NCERT Solutions for Class 10

Candidates who are preparing for the Class 10 board examination must be aware of NCERT Solutions for Class 10. Class 10 plays a major role in choosing the career stream at the higher secondary level. So students who want to shine in grade 10 must score high in Class 10. For that having the detailed knowledge of the NCERT Solutions Class 10 is a must. From the following table, students can find NCERT Solutions for Class 10. With the help of class 10, NCERT solutions students will not only make a good grade in class 10 but will be also able to crack the competitive exams without any difficulty.

NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources

NCERT Solutions For Class 10 Science Chapter 16 Management Of Natural Resources: In this article, we will provide you all the necessary information regarding NCERT Solutions For Class 10 Science Chapter 16 Management Of Natural Resources. Along with the NCERT Solutions for the 16th chapter, we have also included management of natural resources class 10 important questions.

So with the help of this management of natural resources class 10 questions and answers you can easily score good marks in the subject science. Read on to find out everything about NCERT solutions for class 10 science chapter 16 to secure good marks in the subject Science.

Before getting into the details of management of natural resources class 10 exercise solutions, let us have an overview of topics and sub topics under the management of natural resources class 10 notes:

  1. Sustainable Management Of Natural Resources
  2. Why Do We Need To Manage Our Resources?
  3. Forests And Wildlife
  4. Water For All
  5. Coal And Petroleum
  6. An Overview Of Natural Resource Management

Free download NCERT Solutions for Class 10 Science Chapter 16 Management Of Natural Resources PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 16 Intext Questions

Page Number: 271

Question 1
What changes can you make in your habits to become more environment friendly ?
Answer:
(i) Segregate waste into recyclable and non-recyclable parts.
(ii) Switch off the lights, fans, television and other electrical appliances when not used.
(iii) Use energy efficient electrical appliances.
(iv) Walk for nearby shops instead of using vehicles.
(v) Reuse paper, plastic and glass bottles.
(vi) Reuse water from washing machines for cleaning purposes.

Question 2
What would be the advantages of exploiting resources with short term aims?
Answer:
The advantage of exploiting resources with short term aim would be self-centred satisfaction. They provide immediate advantages.

Question 3
How would these advantages differ from the advantages of using a long term perspective in managing our resources ?
Answer:
This way the resources can be used for the benefit of the present generation and also conserved for the benefit of generations to come. This ensures uniform distribution of resources among the people.

Question 4
Why do you think there should be equitable distribution of resources ? What forces would be working against an equitable distribution of our resources ?
Answer:
There should be equitable distribution of resources so that all, rich, powerful and poor people get benefit from the development of these resources. Rich, greedy and powerful people could work against an equitable distribution of our resources.

Page Number: 275

Question 1
Why should we conserve forest and wild life ?
Answer:
We should conserve forest and wildlife because of the following reasons.

  1. They help in maintaining the ecological balance at a place.
  2. They provide us with useful things like rubber, wood, dyes, gum, resin, oil, fibres, medicines, catachu, wax, honey, fruits, seeds, leaves of bidi etc.
  3. They purify the air, control flood and prevent soil erosion and maintain its fertility.
  4. Forests conserve biodiversity and hereditary resources. Ecological stability gets imbalanced due to damage in diversity.

Question 2
Suggest some approaches towards the conservation of forests.
Answer:
Some methods for forest conservation are as follow :

  1. Only except some trees, there should be ban on cutting of forest. Forests stop soil erosion.
  2. Forests should be saved from fires. Many forests get destroyed due to fires.
  3. Forests should be saved from pests and insects. Pesticides, insecticides should be sprayed in forests.
  4. Overgrazing should be prohibited.
  5. National rules and laws should be strictly enforced.

Page Number: 278

Question 1
Find out about the traditional systems of water harvesting management in your region.
Answer:
Many of us live in cities, where water is supplied by the municipal authorities. In the houses, systems of rainwater harvesting are installed which collect the water running off and channel it into a special pit created for the purpose. This helps to recharge ground water.
Efforts are being made to collect run off rain water in soak pits. This water enriches underground water and can cause rise in water table.
Run off water from roof tops can also be collected in trenches, specially made to enrich underground water table.

Question 2
Compare the above systems with the probable systems in hilly/mountainous areas or plains or plateau regions.
Answer:
Drinking water system in hilly areas :

  • Kuhls were a traditional irrigation system in hilly areas such as Himachal Pradesh. In this system, the water flowing through falls, comes to villages located at lower regions through small human made drains.
  • • In Meghalaya, the water is brought down to the lower areas of hills through bamboo drains.

Drinking water system in plains :

  • Jhalaras were made in Rajasthan and Gujarat, essentially meant for community use and for religious rites.
  • In some places bawaries etc. were made to supply water.

Drinking water system in plateau regions :

  • Bandharas are check dams or diversion which were build across rivers. Such a traditional system was found in Maharashtra.
  • In some regions, small pits were dug to collect water.

Question 3
Find out the source of water in your regions/locality. Is water from this source available to all people living in that area ?
Answer:
The main source of water in our region (Delhi) is river Yamuna, upper Ganga canal, Bhakra storage and ground water. Water after being treated is supplied to the residents through a system of water pipes.
The water is available to all the people living in the area.
(Note : Students should write about the locality (region around them.)

NCERT Solutions for Class 10 Science Chapter 16 Textbook Chapter End Questions

Question 1
What changes would you suggest in your home in order to be environment friendly?
Answer:
We would suggest following changes in our home to make it environment friendly.

  1. Separate wastes into recyclable and non-recyclable.
  2. Use electricity judiciously.
  3. Follow three R’s (Reduce, Recycle and Reuse).
  4. Eat as much as you require but do not waste food.
  5. Use water judiciously.
  6. Reuse newspapers and use less plastic.
  7. Have more windows in the house for natural light.
  8. T.V., fans, lights etc should be turned off while going outside the room. Less use of heaters. Try wearing sweaters instead.
  9. Public transport should be used instead of private vehicles.

Question 2
Can you suggest some changes in your school which would make it environment friendly ?
Answer:
Following changes can be made in schools to make it environment friendly.

  1. Plant enough trees in the school.
  2. Leaking taps should be repaired so that water is not wasted.
  3. Bring food in reusable boxes, not in plastic bags or in aluminium foil.
  4. Teachers can educate students about environmental conservation.
  5. There should be more windows in school for natural light.

Question 3
We saw in this chapter that thue are four main stakeholders when it comes to forests and wild life. Which among these should have the authority to decide the management of forest produce ? Why do you think so ?
Answer:
The people living in and around the forests and the forest department of The Government could be given the authority to manage the forests because the forest department of the Government has sufficient power and resources that can manage the forest resources well. The people living in and around forests know about the forest products and use them only according to their needs. In addition to this, they would not damage the forests and use forests sustainably.

Question 4
How can you as an individual contribute or make a difference to the management of (a) forests and wild life (b) water resources and (c) and petroleum ?
Answer:
(a) As an individual we can contribute the following to conserve forest and wildlife.

  1. Trees should not be cut. If trees needed to be cut, then new trees should be planted in their place.
  2. Trees should be saved from fire.
  3. Forest animals should be protected and their illegal hunting should be prohibited. Sustainable Management of Natural Resources

(b) As an individual we can contribute the following in the management of water resources.

  1. Tap should be closed when water is not in use while brushing, shaving, washing hands.
  2. Protect water sources from getting polluted.
  3. If there is any leak in water distribution system, then repair it or inform concerned agency.

(c) As an individual we can contribute the following in the management of coal and petroleum.

  1. Public transport should be used instead of private vehicle. It saves petrol.
  2. Do not use electricity in vain.
  3. Switch off the vehicle at the red light if you have to wait for too long.
  4. Wear extra sweater instead of using heaters.
  5. Use LPG or CNG.

Question 5
What can you as an individual do to reduce your consumption of the various natural resources ?
Answer:
We can do the following as an individual to reduce our consumption of the various natural resources.

  1. Follow the principle of three R’s i.e., Reduce, Recycle and Reuse.
  2. Plastic bags should be reused for the storage of food and small things.
  3. Food should be taken as per requirement.
  4. Reusable bottles should be used to store water everyday.
  5. The devices based on renewable sources of energy like solar cell, solar heater, etc. should be used.

Question 6
List five things you have done over the last one week to
(a) conserve our natural resources.
(b) increase the pressure on our natural resources.
Answer:
(a) To conserve our natural resources :

  • Saved electricity by switching off the lights, fans, television and other electrical appliances when not needed.
  • Used energy efficient electrical appliances. This is done by using compact fluorescent lamps (CFL) and fluorescent tube lights instead of traditional filament type electric bulbs.
  • Used public transport for school instead of parent’s car.
  • Took bath with less water than before and did not waste water.
  • Took part in community awareness meetings regarding environmental conservation.

(b) To increase the pressure on natural resources :

  • Used more paper than required for printing on my computer.
  • Kept the fan on even when I was not in the room.
  • Wasted food.
  • Burnt crackers.
  • Wasted petrol by unnecessarily starting the motorbike.

Question 7
On the basis of the issues raised in this chapter, what changes would you incorporate in your life-style in a move towards sustainable use of our resources ?
Answer:
We would bring following changes in our lifestyle so that sustainable use of our natural resources can be encouraged.

  1. We should limit our personal and collective needs beyond laws, rules and regulation so that the benefit of development can be made available to all and future generations.
  2. Close the tap when not in use.
  3. Turn off the lights, fans etc. in home, school or office when not in use.
  4. Make least use of polythene bags and these should not be thrown in garbage.

NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources

Management of natural resources: Conservation and judicious use of natural resources. Forest and wildlife; Coal and Petroleum conservation. Examples of people’s participation for conservation of natural resources. Big dams: advantages and limitations; alternatives, if any. Water harvesting. Sustainability of natural resources.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 16
Chapter NameManagement of Natural Resources
Number of Questions Solved16
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Question 1.
What changes can you make in your habits to become more environment-friendly?
Answer:
We should use the formula of three R’s in our home in order to be environment friendly.

  1. Reduce, i.e. to use less, and save the water and the electricity by stopping their wastage.
  2. Recycle, i.e. to segregate the waste so that materials which can be recycled should be dumped in a place for recycling.
  3. Reuse, i.e. to reuse certain materials like bottles Of jams and pickles for storing other kitchen items, etc.

Question 2.
What would be the advantages of exploiting resources with short-term aims?
Answer:
There would be no advantage of exploiting resources with short-term aims. Their exploitation may appear to be advantageous in the short-term but it is highly disadvantageous in the long- term. By doing so, we may be able to enjoy the comforts Of life but we would damage our environment gradually.

More Resources for CBSE Class 10

Question 3.
How would these advantages differ from the advantages of using a long-term perspective in managing our resources?
Answer:
The exploitation of natural resources with short-term aims are advantageous for present generation to meet their daily requirements whereas management of natural resources with long-term perspective are aimed to fulfill the needs of future generation and to maintain their sustainability.
Download NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources PDF

Question 4.
Why do you think there should be equitable distribution of resources? What forces would be working against an equitable distribution of our resources?
Answer:
Everybody has equal rights over natural resources and also everybody should get the benefits from them. Therefore, equitable distribution of resources is essential to ensure that everybody gets their due benefit. But many forces go against the equitable distribution of natural resources. The geographical factors are the most important factors which do not allow equitable distribution of natural resources. Economy is another factor which prevents equitable distribution Of these resources.

Page 273

Question 1.
Why should we conserve forests and wildlife?
Answer:
We should conserve forests and wildlife for preserving our environment. They together maintain an ecological balance Of nature. We should conserve them for our economic and social growth and to meet our material aspirations.

Question 2.
Suggest some approaches towards the conservation of forests.
Answer:
The principles of three R’s should be followed to conserve the forests. In addition to this, all stakeholders should be made a part of any conservation programmes. Also, the interests of local forest dwellers should always be kept in mind while Organising a conservation programme.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
Manu and Dheer goes to same school, but their parents drop and pick them separately. After learning about natural resources and their management, they talked to their parents, who arrived on few decisions. What could be the best possible decisions among those given below.
(a) To walk the small distance to school
(b) Car pool
(c) Use common school bus at nearby stop
(d) All of the above
Answer:
(d) To save the resources like petrol and diesel used in cars, one can walk to their destination, if it is close, car pooling can be done by people sharing same locations, etc. These practice will save the natural resources and reduce environmental pollution.

Question 2.
The pH of water sample collected from a river . was found to be acidic in the range of 3.5 – 4.5. On the banks of the river were several factories that were discharging effluents into the river. The effluents of which one of the following factories is most likely to cause low pH of river water? [NCERT Exemplar]
(a) Soap and detergent factory
(b) Lead battery manufacturing factory
(c) Plastic cup manufacturing factory
(d) Alcohol distillery
Answer:
(b) Lead is a major constituent of lead-acid battery used extensively in car batteries. The discharge from lead battery manufacturing factory can lower the pH of river water by making it acidic.

Question 3.
Varun has read about some national movements associated with conserving environment and its resources. Chipko movement was one tree hugging movement in which the villagers compelled axemen to stop the cutting of trees by embracing and encircling trees. Help him in finding out the person who was not related with this movement?
(a) Rajendera Singh
(b) Gaura Devi
(c) Sunder Lai Bahuguna
(d) Chandi Prasad Bhatt
Answer:
(a) Rajendra Singh was not associated with the Chipko movement. Chipko movement was meant for protection of trees from excessive commercial exploitation and was instigated by Sunder Lai Bahuguna and Chandi Prasad Bhatt.

Question 4.
Due to several human activities, waterbodies are polluted resulting in decreased availability of usable water. Maya was testing the samples of polluted water in lab. The presence of which factor will confirm to her that the water sample is polluted.
Select the correct option.
(a) The presence of coliform bacteria
(b) High BOD
(c) Both (a) and (b)
(d) Either (a) or (b)
Answer:
(c) In polluted water sample, coliform bacteria are present. Biochemical Oxygen Demand is BOD. High BOD indicates that water is polluted.
Coliform bacteria occurs in waterbodies where human excreta and deadbodies are disposed off.

Question 5.
The construction of large dams has faced a lot of oppositions like the Sardar Sarovar Project on river Narmada lead to Narmada Bachao Andolan. Raj has to identify the correct problem that lead to such strong oppositions against construction of such dams.
Choose the correct option.
(a) Large areas of agricultural land and human habitation submerged
(b) Destruction of large ecosystem and loss of biological diversity
(c) Displacement of large number of local population without adequate rehabilitation
(d) All of the above
Answer:
(d) All the given statements are correct. Construction of large dams leads to disappearance of agricultural land, disposal of human habitation.
Thus, disturbing an ecosystem along with its diversity. People are displaced from their homes ” without any recommendation of living space and profession.

Question 6.
Ganga has been considered as a symbol of purity but is grossly polluted by waste dumped in it. Government has been making plans to revive this basin. Which steps should according to you be incorporated in the plan to prevent any further polluting of this river? Choose the correct option.
(a) Renovation of sewage pumps and treatment plants
(b) Extension of sewerage in unsewered areas to bring waste from those areas to treatment plants
(c) Installation of new treatment plants
(d) All of the above
Answer:
(d) All the strategies can be incorporated in the plan of action to make river Ganga pollution free.

Question 7.
Madhur was reading about rainwater harvesting and its benefits. He came to learn about different types of structures that are build in different states to conserve rainwater. Select the correct option which represent such structures.
(a) Bhundhis
(b) Khadins
(c) Both (a) and (b)
(d) Compost pit
Answer:
(c) Khadins and Bhundhis are the traditional rain harvesting systems used in Rajasthan and Madhya Pradesh, Uttar Pradesh, respectively.

Question 8.
A student reading an article on sustainable development came across some statements which confused him. Those statements are being given below.
Choose the incorrect statement from therm by selecting an option.
(a) Economic development is linked to environmental conservation
(b) Sustainable development encourages development for current generation and conservation of resources for future generations
(c) Sustainable development does not consider the view points of stakeholders
(d) Sustainable development is a long planned and persistent development
Answer:
(c) Statement (c) is incorrect because sustainable development do consider the interest of stakeholders, i.e. people with dependency on the natural resources and are affected by any project or its outcome directly or indirectly.

Question 9.
A programme called “silviculture” was started to replenish the forest resource, so as to meet the diverse needs of living beings. According to you, which statements from those given below will not be considered an advantage of this initiative.
(a) It maintains a perfect water cycle in nature
(b) It prevents soil erosion.
(c) It encourages plantation of multipurpose trees in open lands of urban area
(d) It produces a large quantity of raw materials for industry
Answer:
(c) Silviculture encourages plantation of multipurpose trees in open lands of urban area is not advantageous because they can be cut down when necessity for more land crops up is required.

Question 10.
Many international treaties and protocols have been developed and signed by different countries to reduce production of greenhouse gases and environment pollution. A treaty/protocol to reduce C02 emission was
(a) Montreal protocol (1987)
(b) Kyoto protocol (1997)
(c) Helesinki declaration (1989)
(d) None of the above
Answer:
(b) The Kyoto protocol was signed by various countries pledging to regulate the emissions of CO2. India signed this protocol in Aug. 2002 and has reduced its CO2 emission by 5.2% till now.

NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources (Hindi Medium)

NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources Hindi Medium 1
NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources Hindi Medium 2
NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources Hindi Medium 3
NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources Hindi Medium 4
NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources Hindi Medium 5

Class 10 Science Management of Natural Resources Mind Map

MANAGEMENT OF NATURAL RESOURCES
Natural resources are resources that exist without actions of humankind. They can be abiotic (such as air, water, land, mineral, ores, etc) or biotic (such as plants, animals, fossil fuels as they are obtained from decaying organic matter).
Natural resource management is an interdisciplinary field of study that considers the physical, biological, economic and social aspects of handling natural resources. It involves putting resources to their best use for human purposes in addition to preserving natural systems.

Why Do We Need To Manage Our Resources?

  • All the things we use or consume such as food, clothes, books, toys, furniture, tools and vehicles are obtained from resources on this earth.
  • A majority of natural resources is limited.
  • Human population is increasing at a tremendous rate.
  • Utilization of natural resources is increasing at an exponential rate.
  • Need to conserve resources for future generations.
  • Equal distribution of resources for equal benefit.
  • Need to reduce the damage caused to the environment while these resources are either extracted or used.

Forests And Wild Life
Forests are ‘biodiversity hot spots’. Biodiversity hotspots are the regions with very high levels of species richness & high degree of endemism. It is very important to preserve biodiversity we have inherited as loss of diversity may lead to a loss of ecological stability.
Stakeholders
Stakeholders are:

  • The people who live in or around forests are dependent on forest produce for various aspects of their life.
  • The Forest Department of the Government which owns the land and controls the resources from forests.
  • The industrialists who use various forests’ produce, but are not dependent on the forests in any one area.
  • The wild life and nature enthusiasts who want to conserve nature in its pristine form.

When we consider the conservation of forests, we need to look at the stakeholders.
Let us look at an example for this:
The local people depend on forests for their firewood, timber, thatch, food, fruits, nuts, as well as medicine. In addition, their cattle also graze in forest areas or feed on other fodder which is collected from forests.

However, when vast tracts of forests have been converted to monocultures of pine, teak or eucalyptus for industrial use, a large amount of biodiversity in the area was destroyed. In addition, the varied needs of the local people (fodder, herbs, fruits & nuts for food) can no longer be met from such forests.

Hence, conserv ation of forests resources must be done at the broader level and should consider each and every group of stakeholder associated with forests resources.

In other words, while the environment is preserved, the benefits of the controlled exploitation should go to the local people, a process in which decentralised economic growth and ecological conservation go hand in hand.

Example of People’s Participation in the Management of Forests
Amrita Devi Bishnoi, in 1731 sacrificed her life along with 363 others for the protection of’khejri’ trees in Khejrali village near Jodhpur in Rajasthan.

The Chipko Andolan, result of a grass-root level effort to end the alienation of people from their forests. The movement was originated in a remote village called Reni in Garhwal during the early 1970s.

In 1972, the West Bengal Forest Department failed in reviving the degraded Sal forests in the southwestern districts of the state.
With the active and willing participation of the local community, the sal forests of Arabari underwent a remarkable recovery by 1983, a previously worthless forest w’as valued Rs 12.5 crores.

Pollution Of The Ganga
Ganga Action Plan, a multi-crore project came about in 1985 because the quality of the water in the Ganga was very poor. Several factors responsible for this poor condition of the river are:

  • Hundred of towns & cities pour their garbage and excreta into it.
  • Large amount of untreated sewage is dumped into the Ganges every day.
  • In addition, human activities like bathing, washing of clothes & immersion of ashes or un-burnt corpses also lead to the huge amount of pollution in the river.
  • Lastly, industries contribute chemical effluents to the Ganga’s pollution load which kills fish in large sections of the river.

Three R’s
Reduce: This means that you use less. For e.g. saving electricity by switching off unnecessary lights & fans, save water by repairing leaky taps etc.
Recycle: This means that you collect plastic, paper, glass & metal items & recycle these materials to make required things instead of synthesising or extracting fresh material. It requires proper segregation of wastes to prevent the dumping of recyclable materials along with other wastes.
Reuse: In this strategy, one simply use things again & again for e.g. plastic or glass bottles used for packaging of food can be used for storing things in the kitchen.

Coal And Petroleum
Coal and petroleum were formed from the degradation of bio-mass millions of years ago & hence they will be exhausted in the future no matter how carefully we use them i.e. they are exhaustible resources.
The management of these resources includes sustainable use of these resources, finding the alternative in forms of renewable energy such as solar energy, wind energy, geothermal energy etc, and increasing the efficiency of our machines or automobiles.

Water Conservation
Dams: Large dams can ensure the storage of adequate water for irrigation as well as for generating electricity.
Canal systems leading from these dams can transfer large amounts of water to greater distances. For e.g. Indira Gandhi Canal has brought greenery to considerable areas of Rajasthan.
However, constructions of large dams address three problems in particular:

  • Social problems as they displace large no. of peasants & tribals without adequate compensation or rehabilitation.
  • Economic problems, they invest huge amounts of public money without the generation of proportionate benefits.
  • Environmental problems, they contribute enormously to deforestation & loss of biological diversity.
  • Water Harvesting: Watershed management emphasises scientific soil and water conservation in order to increase the biomass production.
  • Various organisations have been working on rejuvenating ancient systems of water harvesting as an alternative to the ‘mega-projects’ like dams.
  • These communities have used hundreds of indigenous water saving methods such as dug small pits & lakes, put in place simple watershed systems, built small earthen dams, constructed dykes, sand & limestone reservoirs, and set up rooftop water-collecting units. This has recharged groundwater levels & even brought rivers back to life.
  • Water harvesting is an age-old concept in India for e.g. khadins, tanks & nadis in Rajasthan, bandharas & tals in Maharashtra, bundhis in Madhya Pradesh & Uttar Pradesh, altars & pyncs in Bihar, kulhs in Himachal Pradesh, ponds in the Kandi belt of Jammu region, eris (tanks) in Tamil Nadu, surangams in Kerala, and kattas in Karnataka.
  • Their main purpose of water harvesting is not to hold surface water but to recharge the ground water beneath. The advantages of storing ground water are:
    • It does not evaporate, but spreads out to recharge wells & provides moisture for vegetation over a wide area.
    • It does not provide breeding grounds for mosquitoes.
    • Ground-water is also relatively protected from contamination by
      NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources Mind Map 1

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NCERT Solutions for Class 10 Science Chapter 15 Our Environment

NCERT Solutions For Class 10 Science Chapter 15 Our Environment: Students searching for NCERT solutions for class 10 science chapter 15 notes can refer to this article. Also, students can find our environment class 10 extra questions and answers. Solving these NCERT Solutions For Class 10 Science Chapter 15 Our Environment will not only help students to secure good marks in board exams but also helps in cracking the competitive exams like JEE Main, NEET, JEE Advanced, etc., According to new CBSE Exam Pattern, MCQ Questions for Class 10 Science pdf Carries 20 Marks.

So students are advised to go through this detailed NCERT Solutions For Class 10 Science Chapter 15 Our Environment to build a strong foundation in the subject Science. Read on to find out everything about cbse class 10 biology our environment NCERT Solutions.

Before getting into the details of our environment class 10 extra questions and answers, let’s have an overview of topics and subtopics under Class 10 Science Chapter 15 Our Environment:

  1. Our Environment
  2. Eco-System — What Are Its Components?
  3. How Do Our Activities Affect The Environment?

Free download NCERT Solutions for Class 10 Science Chapter 15 Our Environment PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 15 Intext Questions

Page Number: 260

Question 1
What are trophic levels ? Give an example of food chain and state the different trophic levels in it.
Answer:
Trophic Levels : The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels.
Example : A food chain operating in a grassland is given below :
Grass → Insects → Frog → Birds
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Intext Questions Page 260 Q1
In this food chain

  1. Grass represents first trophic level.
  2. Grasshopper represents second trophic level.
  3. Frog represents third trophic level.
  4. Eagle represents fourth tropic level.

Question 2
What is the role of decomposers in the ecosystem ?
Answer:
(i) Decomposers help in decomposing the dead bodies of plants and animals and hence act as cleansing agents of the environment.
(ii) Decomposers also help in putting back the various elements of which dead plants and animals are made, back into the soil, air and water for reuse by the producers like crop plants.
(iii) They help in recycling of the nutrients.
(iv) They decompose dead remains thereby providing space for new life to settle in the biosphere.

Page Number: 262

Question 1
Why are some substances biodegradable and some non-biodegradable ?
Answer:
The microorganism like bacteria and other decomposer organisms (called saprophytes) present in our environment are specific in their action. They break down the materials or products made from natural materials (say, paper) but do not break down man-made materials such as plastics. So, it is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable, whereas others are non-biodegradable.

Question 2
Give any two ways in which biodegradable substances would affect the environment.
Answer:
(i) Biodegradable substances are decomposed by the action of microorganisms and decomposed materials are recycled through geo-chemical cycle.
(ii) These substances keep the environment clean.

Question 3
Give any two ways in which non-biodegradable substances would effect the environment.
Answer:
(i) They cause air, water and soil pollution.
(ii) They may cause bio-magnification in the food chain and end up in humans.

Page Number: 264

Question 1
What is ozone and how does it affect any ecosystem ?
Answer:
Ozone (O3) is an isotope of oxygen, i.e., it is a molecule formed by three atoms of oxygen.
At the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiations from the sun. These radiations are highly damaging to organisms. Ultraviolet rays can cause skin cancer.

Question 2
How can you help in reducing the problem of waste disposal ? Give any two methods.
Answer:
(i) Recycling : The solid wastes like paper, plastics and metals, etc. are recycled.
(ii) Preparation of Compost: Biodegradable domestic wastes such as left over food, fruit and vegetable peels and leaves of potted plants, etc. can be converted into compost by burying in a pit dug into ground.

NCERT Solutions for Class 10 Science Chapter 15 Textbook Chapter End Questions

Question 1
Which of the following groups contain only biodegradable item ?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit peels, cake and lime juice
(d) Cake, wood and grass
Answer:
(a) Grass, flowers and leather.

Question 2
Which of the following constitutes a food-chain ?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer:
(b) Grass, goat and human.

Question 3
Which of the following are environment friendly practices ?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop on her scooter
(d) All of the above
Answer:
(d) All of the above.

Question 4
What will happen if we kill all the organisms in one trophic level ?
Answer:
The food chain would end and ecological balance would be affected.

  1. If the herbivores are killed, then the carnivores would not be able to get food and would die.
  2. If carnivores are killed, then the population of herbivores would increase to unsustainable level.
  3. If producers are killed, then the nutrient cycle in that area would not be completed.

Question 5
Will the impact of removing all the organisms in a trophic level be different for different trophic levels ? Can the organisms of any trophic level be removed without causing any damage to the ecosystem ?
Answer:
Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example, on removing producers; herbivores would not be able to survive or they would migrate and ecosystem would collapse. If herbivores are removed, producers would grow unchecked and carnivores would not get food. If carnivores are removed, herbivores would increase to unsustainable levels and could destroy the producers. If decomposers are removed, the dead animals would pile up due to which the environment would become polluted. In addition to this, if dead animals will not decompose, the recycling of nutrients in the soil will be stopped and its fertility will be reduced. As a result the green cover of the earth will be lost. Thus to maintain the balance of the ecosystem the presence of organisms is necessary at each trophic level.

Question 6
What is biological magnification ? Will the levels of this magnification be different at different levels of the ecosystem ?
Answer:
Biological magnification : The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification.
Yes, levels of bio-magnification would increase as the trophic level increases and would be the highest for topmost trophic level. It would affect their biological process such as growth, reproduction, etc.

Question 7
What are the problems caused by the non-biodegradable wastes that we generate ?
Answer:
The problems caused by the non-biodegradable wastes are :

  1. If the quantity of non-biodegradable matter increases in the nature then bio-magnification of poisonous chemicals in our body increases.
  2. If the non-biodegradal waste keeps on increasing there will not be left any substance for new organisms.
  3. The increasing quantity of non-biodegradable waste will cause imbalance of ecosystem.

Question 8
If all the waste we generate is biodegradable, will this have no impact on the environment ? [CBSE 2011, 2013]
Answer:
If all the waste we generate is biodegradable, it will also have impact on the environment. If it is disposed off properly, the problem of air, water and soil pollution can be lessened to an extent. There would be less health problems and humans would be disease-free.
But if it is not disposed off properly, it will affect the environment adversely.

Question 9
Why is damage to the ozone layer a cause for concern ? What steps are being taken to limit this damage ?
Answer:
The damage to the ozone layer is a cause for concern because if the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiations coming from the sun would reach the earth. These ultraviolet radiations would cause skin cancer and other ailments in men and animals and also damage the plants.
In an attempt to protect the ozone layer, the United Nations Environment Programme (UNEP) unanimously forged an agreement among its member countries to freeze CFC production at 1986 levels.

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Our environment: Eco-system, Environmental problems, Ozone depletion, waste production and their solutions. Biodegradable and non-biodegradable substances.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 15
Chapter NameOur Environment
Number of Questions Solved16
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Page 257

Question 1.
Why are some substances biodegradable and some non-biodegradable ?
Answer:
Substances that are broken down by biological processes are said to be biodegradable. In our environment, many of the substances are broken easily by decomposers (bacteria and fungi) as they possess specific enzymes for such activity. However, there are other substances also which are not broken down in this manner and are known as non-biodegradable substances. Since these substances are not degraded by bacteria and fungi, so they persist for a long time. These non-biodegradable substances will be acted upon by physical processes like heat and pressure.

Question 2.
Give any two ways in which biodegradable substances would affect the environment.
Answer:

  1. They may produce foul smell during decomposition process.
  2. They may produce some harmful gases such as ammonia, methane, carbon dioxide, etc., which can further-cause global warming.

More Resources for CBSE Class 10

Question 3.
Give any two ways in which non-biodegradable substances would affect the environment.
Answer:

  1. These inert substances simply persist in the environment. This means that these substances require land area for dumping.
  2. Excess of fertilizers, pesticides and other chemicals changes soil chemistry and also affects aquatic life.
  3. Most of these chemicals and heavy metal are easily absorbed by the organisms. This causes biological magnification.

Download NCERT Solutions for Class 10 Science Chapter 15 Our Environment PDF

Page : 261

Question 1.
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer:
Each step or level of the food chain forms a trophic level. Consider the following food chain:

NCERT Solutions for Class 10th Science Chapter 15_1

Question 2.
What is the role of decomposers in the ecosystem?
Answer:
Role of decomposers in the ecosystem :

  1. They help in breaking down the complex organic into simple inorganic that go into the soil and are used up by the plants.
  2. They the nutrient pool of the putting In this way, ad as cleansing agents of nature.
  3. They help in maintaining the fertility of by adding humus content to it.

Page : 264

Question 1.
What is ozone and how does it affect any ecosystem?
Answer:
Ozone (O3) is a molecule formed by three atoms of oxygen. At the higher of the atmosphere, it shields the surface of the earth from ultraviolet (UV) radiation from the Sun. It may affect any ecosystem in the following ways :

  1. At the surface of the earth, it is a deadly poison for all lower forms of life.
  2. If this layer gets depleted, then it may cause cancer in human beings including other plants and animals.

Question 2.
How can you help in reducing the problem of waste disposal? Give any two methods?
Answer:

  1. By changing our lifestyle and change in attitude will reduce disposable waste.
  2. Reducing packaging.
  3. Recycling of waste.
  4. Preparing compost of biodegradable waste.

Excercise:

Question 1.
Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Answer:
(c) Fruit-peels, cake and lime-juice and (d) Cake, wood and grass

Question 2.
Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer:
(b) Grass, goat and human

Question 3.
Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
Answer:
(d) All of the above

Question 4.
What will happen if we kill all the organisms in one trophic level?
Answer:
If we kill all the organisms in one trophic level, then transfer of energy as well as matter to next higher level will stop. It will lead to over- population at one particular level causing amongst the individuals. This would seriously disturb the food chain and can cause the collapse of an ecosystem even.

Question 5.
Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Answer:
Yes, the impact Of removing all the Organisms in a trophic level will be different for different trophic levels. It will not be possible to remove any organism in any trophic level without causing damage to the ecosystem.

Question 6.
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer:
The accumulation of harmful chemicals in the body of living organisms at different trophic levels in a food chain is called biological magnification. Yes, the concentration of these harmful chemicals will be different at different trophic levels. It will be maximum at the last trophic levels which is mostly of the top carnivores (quaternary consumers).

Question 7.
What are the problems caused by the non-biodegradable wastes that we generate?
Answer:
(i) Non-biodegradable wastes persist in the environment for a long time and cause greater harm to the various members of the ecosystem by causing biological magnification.
(ii) Non-biodegradable waste such as fertilizers, pesticides, weedicides, etc., changes the soil chemistry. in turn affects the fertility of soil and subsequently reduces the crop yield.

Question 8.
If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer:
Biodegradable waste will be recycled easily by the decomposers such as bacteria and fungi. It will have only this bad impact on our environment that, many Of the gases released during decomposition process may result in global warming.

Question 9.
Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer:
The ozone shields the surface of the earth from ultraviolet (UV) radiation from the sun. These radiations are highly damaging as they can cause cancer in both plants and animals, damage to eyes and immune system. They can also lead to variations in global rainfall, ecological disturbances and dwindling of global food supplies. Due to these reasons, damage to the ozone layer is a major cause for concern.
Steps which are taken to limit this damage :

  1. To decrease the use of synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.
  2. In 1987, the United Nations Environment Programme (UNEP) succeeded in reaching an agreement to freeze CFC production at 1986

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
Identify the original source of the energy which flows through a food chain?
(a) Carbon dioxide
(b) Glucose
(c) Oxygen
(d) Sunlight
Answer:
(d) All the living organisms get energy directly or indirectly from the sunlight reaching the surface of Earth.

Question 2.
A teacher draws the pyramid of energy on board and writes A, B, C and D, in each trophic level as shown in the diagram given alongside. Which level represents the herbivores?
NCERT Solutions for Class 10 Science Chapter 15 Our Environment MCQs Q2
(a) A
(b) B
(c) C
(d) D
Answer:
(c) The trophic levels represent the transfer of food or energy through various steps or levels in the food chain. Producers harness the maximum energy followed by primary consumers, i.e. a herbivore, which is represented by C in thg given diagram.

Question 3.
Which of the following groups contains only biodegradable items? [NCERT]
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Answer:
(a), (c) and (d) substances that are broken down (decomposed) by the biological processes are said to be biodegradable e.g. fruit-peels, cake, lime-juice, wood, grass, leather, flowers, etc.

Question 4.
Which of the following constitutes a food-chain? [NCERT]
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer:
(b) Each step of food chain form a trophic level. Producers (grass) forms the first trophic level, herbivore (goat) the second and carnivore (human) the third trophic level.

Question 5.
Which of the following are environment- friendly practices? [NCERT]
(a) Carrying cloth-bags to put purchases ‘ while shopping .
(b) Switching off unnecessary light and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
Answer:
(d) Cloth-bags are biodegradable, switching off unnecessary light and fans conserves electricity and limited use of petrol/diesel causes less pollution. Hence, all these practices are considered as environment friendly.

Question 6.
Which of the following statements about food chain are correct?
(a) It includes repeated eating, i.e. each group eats the other and is subsequently eaten by some other group of organisms.
(b) It shows a series of branching lines and unidirectional flow of energy.
(c) It shows the unidirectional flow of energy and proceeds in a progressive straight line.
(d) Both (a) and (c)
Answer:
(d) A food chain is a series of organisms in an environment through which energy transfer occurs starting with a producer. It proceeds in straight line. Food chain does not consist of branching lines.

Question 7.
In class, the teacher explained the concept of food chain and energy flow. She made a diagram as given below and asked the students to identify the producer organism in the chain. What do you think will be the student’s answer?
NCERT Solutions for Class 10 Science Chapter 15 Our Environment MCQs Q7
Answer:
(b) Cabbage is the producer component of this chain. It produces food using sunlight and other components by photosynthesis process. Others are all consumers.

Question 8.
An ecosystem includes
(a) all living organisms
(b) non-living objects ,
(c) both living organisms and non-living objects
(d) sometimes living organisms and sometimes non-living objects
Answer:
(c) All the interacting organisms in an area taken together with the non-living constituents of the environment form an ecosystem. Thus, an ecosystem consists of biotic components including all living organisms and abiotic components constituting physical factors like temperature, rainfall, wind, soil and minerals.

Question 9.
In the following groups of materials, which group (s) contains only non-biodegradable items?
(i) Wood, paper, leather
(ii) Polythene, detergent, PVC
(iii) Plastic, detergent, grass
(iv) Plastic, bakelitC DDT
(a) (iii)
(b) (iv)
(c) (i) and (iii)
(d) (ii) and (iv)
Answer:
(d) Substances that cannot be broken down by biological processes in nature are non-biodegradable. e.g. polythene, detergent, PVC, plastics, bakelite, DDT, etc. On the other hand, substances that are broken down (decomposed) by biological processes are said to be biodegradable, e.g. wood, paper, leather, grass, animal bones, etc.

Question 10.
Which of the following statement is incorrect?
(a) All green plants and blue-green algae are producers.
(b) Green plants get their food from organic compounds.
(c) Producers prepare their own food from inorganic compounds.
(d) Plants convert solar energy into chemical energy.
Answer:
(b) Green plants prepare their food from inorganic compounds using radiant energy of the sun in the presence of chlorophyll. All green plants and blue-green algae are called producers as they can prepare food from inorganic substances by photosynthesis. Producers capture the solar energy and convert it into chemical energy.

Question 11.
What will happen if deer is missing in the food chain given below?
Grass → Deer → Tiger
(a) The population of tiger increases.
(b) The population of grass decreases.
(c) Tiger will start eating grass.
(d) The population of tiger decreases and the population of grass increases.
Answer:
(d) If deer is missing in the given food chain, there will not be sufficient food for the tigers. Some of the tigers will die because of starvation and hence, the population of tigers will decrease. Since, grass is eaten by deers, the population of grass will also increase whefl deer is missing.

Question 12.
In a class activity, two students were asked to collect different items from their fellow mates and classify them as biodegradable and non- biodegradable. All the items have been identified except three. Find out which one is non-biodegradable among these?
(a) Jute crafted bag
(b) A sharpner
(c) Empty fevistick
(d) Both (b) and (c)
Answer:
(d) Both (b) and (c), i.e. the sharpener and the empty fevistick container. These products are made from plastic and hence are non-biodegradable.

Question 13.
The diagram shows excretory losses from a rat to the environment.
NCERT Solutions for Class 10 Science Chapter 15 Our Environment MCQs Q13
Which of the following will not be returned to the ecosystem and recycled?
(a) carbon dioxide
(b) heat energy
(c) salts
(d) urea
Answer:
(b) Heat energy cannot be recycled, it gets lost in the environment. The generated is returned through the carbon cycle. Salts are used by living organisms present in the ecosystem. Urea also returns to the nitrogen cycle.

Question 14.
Which of the following limits the number of trophic levels in a food chain?
(a) Decrease in energy at higher trophic levels
(b) Deficient food supply
(c) Polluted air
(d) Water
Answer:
(a) Decrease in energy at higher trophic levels limits the number of trophic levels in a food chain. At each trophic level, a large portion of energy is utilised for the maintenance of organisms that occur at that trophic level. So, organisms at higher level gets less and less energy at successive levels. The. number of trophic levels are limited to 3-4 because after that, the energy available for the next level will be too small, i.e. it will be insufficient to sustain life of the organisms.

Question 15.
If a grasshopper is eaten by a frog, then the energy transfer will be from
(a) producer to decomposer
(b) producer to primary consumer
(c) primary consumer to secondary consumer
(d) secondary consumer to primary consumer
Answer:
(c) In a food chain, if a grasshopper is eaten by a frog, then the energy transfer will be from primary consumer to secondary consumer. Grasshopper feeds on producers i.e. the grass/plants. So, it occupies the level of primary consumer. Frogs, eating grasshopper thus become the secondary consumer.

Question 16.
In the given food chain, suppose the amount of energy at fourth trophic level is 5 kJ, what will be the energy available at the producer level?
Grass → Grasshopper → Frog → Snake → Hawk
(a) 5 kJ
(b) 50 kJ
(c) 500 kJ
(d) 5000 kJ
Answer:
(d) According to 10% law, only 10% of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level. In this food chain, at the 4th trophic level, only 5 kJ energy is available to the snake. So, the energy available at the producer level will be 5000 kJ.
It can be shown as
NCERT Solutions for Class 10 Science Chapter 15 Our Environment MCQs Q16

NCERT Solutions for Class 10 Science Chapter 15 Our Environment (Hindi Medium)

NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 1
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 2
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 3
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 4
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 5
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NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 8
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 9
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 10
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 11
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 12
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Hindi Medium 13

Class 10 Science Our Environment Mind Map

Eco-system
It is defined as functional unit of nature, where living organisms interact among themselves and also with the surrounding physical environment.
Hence, there are two main components of the ecosystem:
Biotic: Living organisms such as plants, animals, microorganisms and humans.
Abiotic: It includes physical factors such as temperature, rainfall, wind, soil and minerals.
Examples of natural ecosystem: forests, ponds, lakes, etc, and human made or artificial ecosystems are gardens, crop-fields, aquarium etc.

Ecosystem consists of various organisms which can be classified as producers and consumers.
Producers are the organisms which make organic compounds like sugar, starch, etc from inorganic substances with the help of sunlight and chlorophyll.

Consumers are the organisms which are dependent on producers for their nutrition. They can be grouped as herbivores, carnivores, omnivores, parasites, and decomposers.

Decomposers are the microorganisms (bacteria & fungi) which break down complex organic substances (dead remains & waste material of living organisms) into simpler inorganic substances that go back into the soil and are used up again by the plants.
Thus, they help in proper cycling of the nutrients in an ecosystem.

Have you ever wondered why we need to clean aquarium but not lakes or ponds?
It is because aquarium is an artificial and incomplete system which lacks producers, food chains, and decomposers.
Hence, it lacks natural nutrients recycling and self¬cleaning abilities. In contrast lake or ponds are natural and complete ecosystem where there is perfect recycling of nutrients and thus does not need to be cleaned very often.

Waste Material
Waste material can be broadly classified into two categories depending on their degradation:

Biodegradable Waste

  • These are the wastes that can be broken down into simpler compounds by the action of bacteria or other saprophytes.
  • In addition, physical processes such as high temperature and pressure also act on them however, under ambient conditions these substances persist in our environment for a very long time.
  • Some examples of such wastes are food materials, kitchen wastes, and other natural wastes.
  • Non-biodegradable Waste
  • These are the substances that are not broken down into simpler compounds by the action of microorganisms.
  • These substances may be inert and simply persist in the environment for a long time or may harm the various members of the eco-system.
  • They are the main causes of air, water and soil pollution and diseases like cancer.
  • Some examples of such waste are plastic, cans, metals, and chemicals for agricultural and industrial purposes.

Food Chains And Webs
In an ecosystem, there exists a series of organisms feeding on one another. This series or organisms taking part at various biotic levels form a food chain. Alternatively, food chain can be defined as a linear network of food or energy flow starting from producer and ending at apex predator.

Trophic Level
Based on the source of their nutrition or food, organisms occupy a specific place in food chain that is known as their trophic level. There are usually four trophic levels:

  • I trophic level: It includes producers or autotrophs for e.g. phytoplankton, grass, trees etc.
  • II trophic level: It includes primary consumer or herbivores for e.g. zooplanktons, grasshoppers, cow etc.
  • III trophic level: It includes secondary consumer or small carnivore for e.g. birds, fishes, wolf etc.
  • IV trophic level: It includes tertiary consumers or larger carni vores for e.g. level lion, tiger, man etc.

Energy Flow

  • The flow of energy is unidirectional.
  • The green plants in a terrestrial ecosystem capture about 1 % of the energy of sunlight that falls on their leaves and convert it into food energy.
  • On an average only 10% organic matter is present at each step and reaches the next level of consumers. It is because a great deal of energy is lost as heat to the environment and rest goes into digestion, in doing work and in growth & reproduction.
  • In addition, the loss of energy at each step is so great that very little usable energy remains after four trophic levels and this is the reason that a food chain usually contain maximum of four trophic levels.
  • Generally, there are greater number of individuals at lower trophic levels of an ecosystem (the greatest number is of the producers)
  • The length and complexity of food chains vary greatly.
    • Each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms.
    • So instead of a straight line food chain, the relationship can be shown as a series of branching lines called a food web.
      NCERT Solutions for Class 10 Science Chapter 15 Our Environment Mind Map

Environmental Problems
Depletion of the ozone layer: Ozone (O3) is a molecule formed by three atoms of oxygen. It is located in upper part of the atmosphere called stratosphere and it acts as shield absorbing UV radiation from sun.

  • At higher levels of atmosphere, high energy UV radiations split apart some moleculer oxygen (O2) into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to form ozone.
  • Ozone depletion permits entry of harmful UV radiations which lead to diseases like skin aging, irritation & cancer, snow- blindness, cataract, etc.
  • Ozone-depleting substances: CFCs, HCFCs, hydrobromofluorocarbons, etc.

Waste disposal: Improvements in our life-style have resulted in greater amounts of waste material generation. For e.g. increased use of disposable items, plastic bags, packing materials etc have resulted in much of our waste becoming non-biodegradable.

Following methods can be helpful in managing the garbage we produce: categorization of waste materials into biodegradable, recyclable & non-biodegradable, reduction in use of non- biodegradable substances such as plastics, thermocol etc, burning & proper dumping of waste.

It is interesting note that how unknowingly some harmful chemicals enter our bodies through the food chain.
It happens by two ways:
Overuse of several pesticides: These chemicals are either washed down into the soil or into the waterbodies.
From the soil, these are absorbed by the plants along with water and minerals, and from the water bodies these are taken up by aquatic plants and animals

Biological magnification: It is defined as an increase in the concentration of the toxicant at successive trophic levels.
These chemicals are not degradable and the organism can neither metabolize nor excrete them and thus they get accumulated progressively at each trophic level.
In addition, human beings occupy the top level in any food chain and thus a maximum concentration of these chemicals gets accumulated in our bodies.

Now that you are provided all the detailed information regarding NCERT Solutions For Class 10 Science Chapter 15 Our Environment and we hope this detailed article on class 10 science chapter 15 NCERT solutions is helpful. If you have any questions regarding this article or  NCERT Solutions For Class 10 Science Chapter 15 Our Environment, drop your comments in the comment box below and we will get back to you as soon a possible.

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

NCERT Solutions For Class 10 Science Chapter 14 Sources Of Energy: Candidates who are searching for NCERT Solutions For Class 10 Science Chapter 14 Sources Of Energy can refer to this article. Sources of energy class 10 NCERT solutions pdf were solved by best physics faculty in India to provide strong command over the Physics subject.

Solving cbse class 10 physics sources of energy questions and answers will not only help candidates in making a good grade in board exams but also helps in cracking the competitive exam such as JEE, JEE Advanced, NEET, JIPMER etc., NCERT Solutions for sources of energy class 10 questions and answers were solved keeping various parameters in mind such as marking scheme, step marks, etc.,

So the candidates who wish to bag a decent score in the unit of sources of energy class 10 Science can scroll down to find out the NCERT Solutions For Class 10 Science Chapter 14.

Before getting into the details of Sources Of Energy Class 10 NCERT Solutions, let us look at the topics and subtopics under class 10 science chapter 14 notes:

  1. Sources Of Energy
  2. What Is A Good Source Of Energy?
  3. Conventional Sources Of Energy
  4. Alternative Or Non-Conventional Sources Of Energy
  5. Environmental Consequences
  6. How Long Will An Energy Source Last Us?

Free download NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 14 Intext Questions

Page Number: 243

Question 1
What is a good source of energy?
Answer:
A good source of energy is one that

  1. does a large amount of work per unit volume or mass
  2. can be easily accessible
  3. is easy to store and transport, and
  4. is economical.

Question 2
What is a good fuel ?
OR
Write any three characteristics of a good fuel. [AICBSE 2015]
Answer:
A good fuel is one which has the following properties :

  1. It should be fairly cheap.
  2. It should be easily available.
  3. Its ignition temperature should be well above normal temperature.
  4. It should be conveniently handled and transported.
  5. It should not produce any poisonous material during burning.
  6. Its combustion rate should be steady and controllable.
  7. It should not leave any residue or ash after burning.
  8. A good fuel should have high calorific value so that higher amount of heat may be obtained by burning a little fuel.

Question 3
If you could use any source of energy for heating your food, which one should you use and why ?
Answer:
I would prefer to use cooking gas like LPG. It fulfils many of the criteria of a good fuel like its ignition temperature, good calorific value and non-polluting characteristics.

Page Number: 248

Question 1
What are the disadvantages of fossil fuels ?
Answer:
(i) The burning of fossil fuels produces large amount of carbon dioxide that causes increased greenhouse effect.
(ii) The burning of fossil fuels (such as coal) produces smoke which pollutes the air.
(iii) The burning of fossil fuels produces acidic gases such as sulphur dioxide and nitrogen oxide. These acidic gases cause acid rain that affects our water and soil resources.
(iv) Fossil fuels cannot be replenished in short time because it takes millions of years to form them.

Question 2
Why are we looking at alternate sources of energy ?
Answer:
We are looking at alternate sources of energy because of the following reasons.

  • The fossil fuels and nuclear fuels on the earth are limited which may not last for long.
  • The undesirable effects of pollution, both from the burning of fossil fuels and from the radioactive nuclear wastes of nuclear power plants are creating threat to our environment.

Question 3
How has the traditional use of wind and water energy been modified for convenience ?
Answer:
(i) Wind mill farms are constructed to produce electricity.
(ii) The traditional use of energy of flowing water has been modified by establishing hydro-power plants. At hydro-power plants, the energy of falling water or flowing water is tapped by using a water turbine and then made to drive generators.

Page Number: 253

Question 1
What kind of mirror-concave, convex or plane – would be the best suited for use in a solar cooker ? Why ?
Answer:
A concave mirror would be best suited in a solar cooker because it focuses the sunlight in a very small area of the solar cooker and a high temperature is produced in it which is sufficient to cook the food.

Question 2
What are the limitations of the energy that can be obtained from the oceans?
Answer:
The energy from the oceans can be obtained mainly in three forms. These are
(i) tidal energy
(ii) wave energy and
(iii) ocean thermal energy

  • Limitations of Tidal Energy :
    (i) There are very few sites around the world which are suitable for building tidal dams.
    (ii) The rise and fall of sea-water during high and low tides is not enough to generate electricity on a large scale.
  • Limitations of wave energy : The movement of ocean waves is associated with kinetic energy. Such sites in the world are limited where the waves strike the shore lines with sufficient power.
  • Limitations of ocean thermal energy : NCERT Solutions for Class 10 Science Chapter 14 Sources of EnergyTo convert ocean thermal energy into electricity, a temperature difference of 20°C (or more) between the surface water of ocean and deeper water is needed for operating OTEC power plants. This involves high cost.

Question 3
What is geothermal energy ?
Answer:
Energy stored as heat in certain regions of the earth (called hot spots) is called geothermal energy. Hot spots are the locations below earth’s crust where upward moving magma gets collected due to geological changes. When underground water comes in contact with the hot spots, steam is generated. This steam is utilised to generate electricity using pipes and turbines. Sometimes hot water from the hot spot finds outlet at the surface. Such outlets are called hot springs.

Question 4
What are the advantages of nuclear energy ?
Answer:
The advantages of nuclear energy are that :

  1. It produces a large amount of useful energy from a very small amount of a nuclear fuel (like uranium-235).
  2. Once the nuclear fuel (like uranium-235) is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. There is no need for putting in nuclear fuel again and again.
  3. It does not produce gases like carbon dioxide which contributes to greenhouse effect or sulphur dioxide which causes acid rain.

Page Number: 253

Question 1
Can any source of energy be pollution free ? Why or why not ?
Answer:
No source of energy can be pollution free because even if it is clean, its assembly could have caused some environmental damage.

Question 2
Hydrogen has been used as rocket fuel. Would you consider it a cleaner fuel than CNG ? Why or why not ?
Answer:
Hydrogen is cleaner fuel than CNG. This is because the burning of hydrogen produces only water, which is totally harmless. On the other hand, burning of CNG produces carbon dioxide gas and water. The carbon dioxide can produce greenhouse effect in the atmosphere and lead to the excessive heating of the environment in long run.

Page Number: 243

Question 1
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer:
(i) Energy derived from biomass is a renewable source of energy because waste products are continuously produced. Plants and trees are also grown at reasonable intervals.
(ii) The energy derived from flowing water, wind, sun and ocean are renewable sources because these sources can be harnessed into energy so long as the present solar system exists.

Question 2
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer:
Fossil fuels like coal and petroleum are exhaustible sources of energy. The estimated reserves of these fuels are said to last us for about another 200 years, while it takes millions of years for these to be formed.

NCERT Solutions for Class 10 Science Chapter 14 Textbook Chapter End Questions

Question 1
A solar water heater cannot be used to get hot water on
(a) a sunny day
(b) a cloudy day
(c) a hot day
(d) a windy day
Answer:
(b) A cloudy day.

Question 2
Which of the following is not an example of a biomass energy source ?
(a) Wood
(b) Gobar gas
(c) Nuclear energy
(d) Coal
Answer:
(c) Nuclear energy.

Question 3
Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the sun’s energy ?
(a) Geothermal energy
(b) Wind energy
(c) Nuclear energy
(d) Biomass
Answer:
(a) Geothermal energy.

Question 4
Compare and contrast fossil fuels and the sun as direct sources of energy Ans
Answer:

Fossil fuelsSun
(i) Non-renewable source of energy.(i) Renewable source of energy.
(ii) Cause a lot of air pollution.(ii) Pollution-free, doesn’t cause any pollution.
(iii) They will exhaust in future.(iii) It is a non-exhaustible source.
(iv) Energy can be tapped throughout the year.(iv) Energy cannot be tapped during night and cloudy and rainy days.

Question 5
Compare and contrast biomass and hydro-electricity as sources of energy. Ans.
Answer:

BiomassHydroelectricity
(i) Renewable source of energy.(i) Renewable source of energy.
(ii) Biomass plants can be installed at any place to produce biomass as energy source.(ii) Plants can be installed only at the places where dams can be constructed.
(iii) To collect waste materials is a tough and costly process.(iii) Once the plants start to work, it is not difficult to collect water.

Question 6
What are the limitations of extracting energy from
(a) the wind ?
(b) waves ?
(c) tides ?
Answer:
(a) Limitations of wind energy
(i) Wind energy farms cannot be established everywhere. The wind energy farms can be established only at those places, where wind blows for most part of the year.
(ii) The wind required for generating electricity should be strong and steady to maintain the desired level of generation. The minimum wind speed necessary for satisfactory working of the wind generator is about 15 km/h. This is not always so.
(iii) The wind energy farms require a large area of land.
(iv) The setting up of wind energy farms is very expensive.

(b) Limitations of wave energy : The harnessing of sea-waves energy would be a viable proposition only at those places where sea-waves are very strong. This has constraints of time and location.

(c) Limitations of tidal energy :
(i) There are very few sites around the world which are suitable for building tidal dams.
(ii) The rise and fall of sea-water during high and low tides is not enough to generate electricity on a large scale.

Question 7
On what basis would you classify energy sources as
(a) renewable and non-renewable ?
(b) exhaustible and inexhaustible ?
Are the options given in (a) and (b) the same ?
Answer:
(a) Renewable sources : The sources of energy which are being produced continuously in nature and are inexhaustible, are called renewable sources of energy. The energy derived from flowing water, wind, tides, ocean waves, or wood are examples of energy from such sources.
Non-renewable sources : These sources are produced over million of years under special conditions. Once consumed, these are not replaceable for a very long time. Fossil fuels like coal, petroleum and natural gas are non-renewable sources.
(b) Exhaustible sources are non-renewable sources, while inexhaustible sources are renewable sources.
Yes, the options given in (a) and (b) are the same.

Question 8
What are qualities of an ideal source of energy ?
Answer:
An ideal source of energy

  • Must give an adequate amount of net energy.
  • Must be convenient to use so as to give energy at a steady rate.
  • Must be easy to store and transport.

Question 9
What are the advantages and disadvantages of using a solar cooker ? Are there places where solar cookers would have limited utility ?
Answer:
Advantages of using solar cooker :

  1. The use of solar cooker for cooking food saves precious fuels like coal, kerosene and LPG.
  2. The use of solar cooker does not produce smoke due to which it does not pollute air.
  3. When food is cooked in solar cooker, its nutrients do not get destroyed. This is because in a solar cooker, food is cooked at a comparatively lower temperature.
  4. In a solar cooker, up to four food items can be cooked at the same time.

Disadvantages of using solar cooker :

  1. The solar cooker cannot be used to cook food during night because sunshine is not available at that time.
  2. If the day sky is covered with clouds, even then solar cooker cannot be used to cook food.
  3. The direction of reflector of solar cooker has to be changed from time-to-time to keep it facing the sun.
    Sources of Energy
  4. The box-type solar cooker cannot be used for baking (making chappattis, etc.) or for frying.
    The places that receive rain most of the year or where the sky remains cloudy, the solar cooker has limited utility.

Question 10
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption ?
Answer:
Some of the environmental consequences of the increasing demand for energy are the following :

  1. The combustion of fossil fuels is producing acid rain and damaging plants (crops), soil and aquatic life.
  2. The burning of fossil fuels is increasing the amount of greenhouse gas carbon-dioxide in the atmosphere. It has also affected the rainfall.
  3. The cutting down of trees from the forest for obtaining fire-wood is causing soil erosion and destroying wild life.
  4. The construction of hydro-power plants is disturbing ecological balance.
  5. Nuclear power plants are increasing radioactivity in the environment.

The following steps can be taken to reduce energy consumption :

  1. Switch off lights, fans, TV. and other such electrical appliances when not needed, to save electricity.
  2. Use energy efficient electrical appliances to save electricity. This can be done by using compact fluorescent lamps (CFL) and tube lights in place of conventional filament- type electric bulbs.
  3. Good quality stoves should be used to burn fuels like kerosene and LPG so as to obtain maximum heat.
  4. Pressure cookers should be used for cooking food to save fuel.
  5. Solar cookers should be used to cook food whenever possible and solar water heaters should be used to get hot water.
  6. The use of biogas as fuel should be encouraged in rural areas.
  7. Bicycles should be used for short distances to save fuel like petrol which is used in cars, scooters and motorcycles.

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

Sources of energy : Different forms of energy, conventional and non-conventional sources
of energy: Fossil fuels, solar energy; biogas; wind, water and tidal energy; Nuclear energy, Renewable versus non-renewable sources of energy.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 14
Chapter NameSources of Energy
Number of Questions Solved24
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Question 1
What is a good source of energy?
Solution:
A good source of energy would be one,
i) Which would do a large amount of work per unit volume or mass.
ii) Be easily accessible.
iii) Be easy to store and transport, and
iv) Perhaps most importantly, be economical.

Question 2
What is a good fuel?
Solution:
A good fuel would be one,
i) Which is easily available.
ii) It should not produce too much of smoke.
iii) On burning should release less amount of heat.

More Resources for CBSE Class 10

Question 3
If you could use any source of energy for heating your food, which one would you use and why?
Solution:
Solar energy can be used for heating food because it is easily available, it will not produce smoke and it will not release any amount of heat.

Download NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy PDF

Question 4
What are the disadvantages of fossil fuels?
Solution:
Fossil fuels are non-renewable. Burning of coal or petroleum products causes the air pollution. The oxides of carbon, nitrogen and sulphur that are released on burning fossil fuels are acid oxides. These lead to acid rain, which affects water and soil resources.

Question 5
Why are we looking at alternate sources of energy?
Solution:
The fossil fuels are non-renewable sources of energy. So we need to conserve them. If we were to continue consuming these sources at such alarming rates, we would soon run out of energy. In order to avoid this, alternate sources of energy were explored.

Question 6
How has the traditional use of wind and water energy been modified for our convenience?
Solution:
The wind possesses kinetic energy. This energy was harnessed by windmills in the past to do mechanical work. Today, wind energy is also used to generate electricity.
Another traditional source of energy was the kinetic energy of flowing water or the potential energy of water at a height. Hydropower plants convert the potential energy of falling water into electricity.

Question 7
What kind of mirror – concave, convex or plane – would be best suited for use in a solar cooker? Why?
Solution:
Plane mirror would be best suited for use in a solar cooker. A plane mirror is used as a reflector. The reflector is used to increase the area over which the solar energy is collected so that more and more heat rays of the sun may enter the solar cooker.

Question 8
What are the limitations of the energy that can be obtained from the oceans?
Solution:
The energy from the oceans can be obtained mainly in three forms,
a) Tidal energy
b) Ocean waves energy
c) Ocean thermal energy
The energy potential from sea is quite large, but efficient commercial exploitation is difficult.

Question 9
What is geothermal energy?
Solution:
‘Geo’ means ‘earth’ and ‘thermal’ means ‘heat’. Thus the geothermal energy is the heat energy from the hot rock present inside the earth. This heat can be used as a source of energy to produce electricity.

Question 10
What are the advantages of nuclear energy?
Solution:
The advantages of nuclear energy is as follows,
(a) It generates electricity.
(b) Disease like cancer can be treated.
(c) It helps for the improvement in the agriculture and industry.

Question 11
Can any source of energy be pollution-free? Why or why not?
Solution:
Yes, Solar energy does not cause any pollution. Solar cells make use of the ‘everlasting solar energy’ and their use does not produce any environmental pollution.

Question 12
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Solution:
Yes, hydrogen is a cleaner fuel than CNG because of its very high colorific value, hydrogen is an extremely good fuel.

Question 13
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Solution:
Hydro Energy and Solar Energy
Hydro energy or water energy is renewable source of electric energy, which will never get exhausted, since water is available in plenty.
Solar energy is also known as light energy, which is obtained from the sun and it will never get exhausted.

Question 14
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Solution:
Coal and petroleum are the two energy sources that are considered to be exhaustible. They are non-renewable sources of energy and are present in a limited amount in the earth. Once exhausted, they will not be available to us again.

Question 15
A solar water heater can be used to get hot water on
(a) a sunny day.
(b) a cloudy day.
(c) a hot day.
(d) a windy day.
Solution:
(a) a sunny day.

Question 16
Which of the following is not an example of a bio-mass energy source?
(a) wood
(b) gobar-gas
(c) nuclear energy
(d) coal.
Solution:
(c) nuclear energy.

Question 17
Most of the sources of energy we use represent stored solar energy.
Which of the following is not ultimately derived from the Sun’s energy?
(a) geothermal energy
(b) wind energy
(c) nuclear energy
(d) bio-mass.
Solution:
(c) nuclear energy.

Question 18
Compare and contrast fossil fuels and the Sun as direct sources of energy.
Solution:
Fossil fuels are non-renewable sources of energy. These non-renewable sources of energy (like coal, petroleum, natural gas) are present in a limited amount in the earth. Once exhausted, they will not be available to us again.
The sun is the source of all energy. The sun is a renewable source of energy, provides us heat and light energy free of cost. The energy obtained from the sun is called solar energy. The energy coming from the sun contains heat rays, visible light, ultra-violet rays and some gamma rays.

Question 19
Compare and contrast bio-mass and hydro electricity as sources of energy.
Solution:
The waste material of living things and the dead parts of living things is called bio-mass. Bio-mass contains carbon compounds and it is the oldest source of heat energy for domestic purposes. The important examples of bio-mass being used as a fuel are wood, cattle dung and agriculture wastes like bagasse.
Hydropower plants convert the potential energy of falling water into electricity. Water energy is a renewable source of electric energy, which will never get exhausted. The construction of dams on rivers helps in controlling floods and in irrigation.

Question 20
What are the limitations of extracting energy from
(a) the wind?
(b) waves?
(c) Tides?
Solution:
a) There are many limitations in harnessing wind energy. Wind energy farms can be established only at those places where wind blows from the greater part of a year. The wind speed should also be higher than 15 Km/h to maintain the required speed of the turbine. There should be some back-up facilities to take care of the energy needs during a period when there is no wind.
b) The waves are generated by strong winds blowing across the sea. Wave energy would be a viable proposition only where waves are very strong.
c) Tidal energy is harnessed by constructing a dam across a narrow opening, the location where such dams can be built are limited.

Question 21
On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?
Solution:
The options given in (a) and (b) are the same.
Those sources of energy, which are being, produced continuously in nature and are inexhaustible are called renewable sources of energy.
Those sources of energy, which have accumulated in nature over a very, very long time and cannot be quickly replaced when exhausted are called non-renewable sources of energy.

Question 22
What are the qualities of an ideal source of energy?
Solution:
The important qualities of an ideal source of energy is
a) It should be a renewable source of energy.
b) It should be pollution-free.
c) It should be economical.
d) It should be easily accessible.

Question 23
What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Solution:
The advantages of a solar cooker
i) The use of solar cooker for cooking food saves fuel.
ii) The use of solar cooker does not produce smoke due to which the environment also does not get polluted.
iii) When food is cooked in a solar cooker, its nutrients do not get destroyed. This is because in a solar cooker, food is cooked at comparatively lower temperature.
iv) In a solar cooker, upto four food items can be cooked at the same time.
The disadvantages of a solar cooker
i) The box-type solar cooker cannot be used to make chappaties.
ii) The box-type solar cooker cannot be used for ‘frying’.
The limited utility of a solar cooker is
i)The solar cooker cannot be used to cook the food during nighttime.
ii) If the day-sky is covered with clouds, even then the solar cooker cannot be used to cook the food.
iii) The direction of reflector of solar cooker has to be changed from time to time to keep it facing the sun.

Question 24
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Solution:
Exploiting any source of energy disturbs the environment in some way or the other. The source we would choose depends on factors such as the case of extracting energy from that source, the economics of extracting energy from the source, the efficiency of technology available and the environmental damage that will be caused by using that source.
We cannot depend on the fossil fuels for much longer, if we manage bio-mass by replacing the trees we cut down for fire-wood, we can be assured of a constant supply of energy at a particular rate. Renewable energy is available in our natural environment, in the form of some continuing or repetitive current of energy, or is stored in such large under ground reservoirs that the rate of depletion of reservoirs because of extraction of usable energy is practically negligible.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
Which of the following is a non-renewable source of energy? [NCERT Exemplar]
(a) Wood
(b) Sun
(c) Fossil fuel
(d) Wind
Answer:
(c) The fossil fuels are non-renewable sources of energy whereas wood, the Sun and wind are renewable sources of energy. Non-renewable sources of energy are those which are exhaustible and cannot be replaced, once they have been used. They are also known as conventional sources of energy.

Question 2.
Fuel used in thermal power plant is [NCERT Exemplar]
(a) water
(b) uranium
(c) bio-mass
(d) fossil fuels
Answer:
(d) The thermal power plant generates electric power from heat produced by burning fossil fuel, i.e. coal and petroleum. Everyday we burn a large amount of fossil fuels to heat up water to produce steam. The steam so produced runs turbines to generate electricity.

Question 3.
In a hydroelectric power plant more electrical power can be generated, if water falls from a greater height because [NCERT Exemplar]
(a) its temperature increases
(b) a large amount of potential energy is converted into kinetic energy
(c) the electricity content of water increases with height
(d) more water molecules dissociate into ions
Answer:
(b) In a hydroelectric power plant, more electrical power can be generated, if water falls from a greater height, because the rise in water level causes the increase in potential energy of water. Thus, when it flows from higher position more amount of kinetic energy is formed by the conversion of higher potential energy and this kinetic energy in the form of moving water can produce more electrical power.

Question 4.
The power generated in a windmill [NCERT Exemplar]
(a) is more in rainy season, since damp air would mean more air mass hitting blades
(b) depends on the height of the tower
(c) depends on wind velocity
(d) can be increased by planting tall trees close to the tower
Answer:
(c) Wind energy farms can be located only in vast open areas located in favourable wind conditions as the minimum velocity for a windmill to functions is 11-16 km/h and is called as cut in speed. Thus, the power generated in a windmill depends on wind velocity.

Question 5.
Choose the correct statement. [NCERT Exemplar]
(a) Sun can be taken as an inexhaustible source of energy
(b) There is infinite storage of fossil fuel inside the Earth
(c) Hydro and wind energy plants are non-polluting sources of energy
(d) Waste from a nuclear power plant can be easily disposed off
Answer:
(a) The Sun has been radiating an enormous amount of energy at the present rate for nearly 5 billion years and will continue radiating at that rate for about 5 billion years more, so the Sun can be taken as an inexhaustible source of energy.

Question 6.
Which part of the solar cooker is responsible for greenhouse effect? [NCERT Exemplar]
(a) Coating with black colour inside the box
(b) Mirror
(c) Glass sheet
(d) Outer cover of the solar cooker
Answer:
(c) Glass sheet present in the solar cooker easily passes the radiation into the solar cooker and the radiation gets absorbed and that reflected back by the black coating is of longer wavelength and cannot pass back out through the glass. Thus, glass sheet produces greenhouse effect in solar cooker.

Question 7.
Ocean thermal energy is due to [NCERT Exemplar]
(a) energy stored by waves in the ocean
(b) temperature difference at different levels in the ocean
(c) pressure difference at different levels in the ocean
(d) tides arising out in the ocean
Answer:
(b) The water at the surface of the sea or ocean is heated by the Sun, while the water in deeper sections is relatively cold. This difference in temperature between these layers ranges from 10-30 °C and is exploited to obtain energy. Thus, ocean thermal energy is due to temperature difference at different levels in the ocean.

Question 8.
The major problem in harnessing nuclear energy is how to [NCERT Exemplar]
(a) split nuclei
(b) sustain the reaction
(c) dispose off spent fuel safely
(d) convert nuclear energy into electrical energy
Answer:
(c) The major hazard of nuclear power generation is the storage and disposal of spent or used fuels. Improper nuclear waste storage and disposal result in environmental contamination as well as risk of accidental leakage of nuclear radiation. It happened in Chernobyl disaster 1986, Fukushima Nuclear disaster 2011 caused great damage to the living beings and habitats.

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy (Hindi Medium)

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 1
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 2
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 3
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 4
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 5
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 6
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 7
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 8
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 9
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 10
NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy Hindi Medium 11

Class 10 Science  Sources of Energy Mind Map

SOURCES OF ENERGY
(Plants, winds, water, coal, bio-gas, natural gas etc.)

It should not affect the environment. It should be eco-friendly.
Biogas is a mixture of methane (75%) CO2, hydrogen and traces of hydrogen sulphide. Methane is an extremely good fuel

Environmential Consequences

  • Air pollution and acid rain
  • Green house effect
  • Damage to water bodies and to human life.

Types of Sources of Energy

  • Renewable Sources of Energy
  • Non- Renewable Sources of Energy

Renewable Sources of Energy
Which can be easily generated and whose supply is unlimited.

Hydro Power Plants
The potential energy of falling water is converted into electricity.

  • Limited Dams
  • Construction needs a large area
  • Eco-systems are destroyed
  • High lost of installation
  • About 20% of the power generated in India comes from hydro power plants

Wind Energy
When wind blows with a sufficient speed, it gets ability to do some work
It doesn’t pollute the air like power plants that rely on combustion of fossil fuels

Wind mill
It is a device which is used to convert wind energy into electrical energy. More than 25% of the electricity needs are generated through a vast network of wind mills.

Wind farm and power plants
It is basically used to generate electricity on a commercial basis, (large scale)
Wind power plants needs high maintenance and high wind speeds
Wind farms are noisy and may spoil the view for people living near them

Biomass
It means any organic matter from which we get energy on a renewable basis

Solar Energy
The energy coming with the rays of the sun. The ultimate source of energy

Solar Cooker
It is a device that uses solar energy to cook food

Solar Panel
It is a combination of large number of solar cells to draw high voltage for commercial purposes

Solar Cells
It is a device which converts solar energy into electric energy
Solar cells can be used in many small appliances like calculators and spacecrafts

Energy from the Sea
Form of energy obtained from the ocean in the form of tidal waves; wind blowing etc.

Tidal energy
It is a form of energy which is obtained from the ocean in the form of tidal waves

Wave energy
It is a another type of ocean based energy source that uses the power of waves to generate electricity

Ocean thermal energy (OTE)
This energy is obtained from using the temperature difference between deep cold ocean water ane warm surface water

Geothermal energy
It is the energy which is stored in the form of heat inside the earth

Characteristics of good sources of energy

  • Easy storing and transportation
  • Easy access
  • Large amount of work per unit volume or mass
  • Economical

Non-Renewable Sources of Energy
Which cannot be generated easily and whose supply is limited

Advantages

  • High in energy
  • Profitable
  • Easy to use
  • Cost effective

Disadvantages

  • Time consuming to extract
  • Dangerous for humans
  • Contribution to acid rain
  • Not viable for future generations

Fossil Fuels
These are hydrocarbons based natural resources that were formed 300 millions years ago.

Thermal Power Plant
Fuel is burnt to produce heat energy which is converted into electrical energy

Advantages

  • Smaller space is required as compared to hydro power plant
  • Running costs are less compared to gas plants or diesel

Major Hazards
Causes Air Pollution Green House Effect and Acid Rain

Nuclear Energy
Energy released during nuclear reactions

Types of Nuclear Energy
Nuclear Fission
It is a process in which a heavy nucleus splits up into two lighter nuclei
92U235 + 0n1
56Ba141 + 36Kr92 + 30n1 + energy

This principle is used in atom bomb

Moderator
Slow down fast moving neutrons e.g.: heavy water, graphite

Coolant
Remove heat e.g.: cold water, liquid oxygen

Control rods
Absorb neutrons e.g.: boron, cadmium

Nuclear Fusion
It is a process in which two lighter nuclei combine together to form a heavier nucleus
1H2 + 1H2 + 1H22He4 + 1H1 + 0n1 + 21.6 Mev

This principle is used in hydrogen bomb

Major Hazards

  • Storage of spent fuels.
  • Disposal of spent fuels.
  • High cost of Installation
  • Limited availability of fuel.

Now that you are provided all the necessary information regarding NCERT Solutions For Class 10 Science Chapter 14 Sources Of Energy and we hope this detailed article on sources of energy class 10 questions and answers are helpful. If you have any doubt regarding this article or cbse class 10 physics sources of energy questions and answers, drop your comments below and we will get back to you at the earliest.

NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current

NCERT Solutions For Class 10 Science Chapter 13 Magnetic Effects Of Electric Current: In this article, you will find out all the necessary information regarding the magnetic effect of electric current class 10 NCERT solutions. So the students who are in search of NCERT Solutions For Class 10 Science Chapter 13 Magnetic Effects Of Electric Current can refer to this article.

Magnetic Effects Of Electric Current Class 10 NCERT questions and answers were solved by the best academic experts in order to help you a better understanding. So the candidates who want to secure a decent grade in class 10 board exams can refer to this article and solve magnetic effect of electric current science class 10 NCERT solutions. Read on to find out everything about NCERT Solutions For Class 10 Science Chapter 13 Magnetic Effects Of Electric Current.

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 13 Magnetic Effects Of Electric Current, let’s have an overview of topics and subtopics under magnetic effect of electric current class 10 NCERT pdf:

  1. Magnetic Effects Of Electric Current
  2. Magnetic Field And Field Lines
  3. Magnetic Field Due To A Current-Carrying Conductor
  4. Force On A Current-Carrying Conductor In A Magnetic Field
  5. Electric Motor
  6. Electromagnetic Induction
  7. Electric Generator
  8. Domestic Electric Circuits

Free download NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects Of Electric Current PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 13 Intext Questions

Page Number: 224

Question 1
Why does a compass needle get deflected when brought near a bar magnet ?
Answer:
The magnetic field of the magnet exerts force on both the poles of the compass needle. The forces experienced by the two poles are equal and opposite. These two forces form a couple which deflects the compass needle.

Page Number: 228

Question 1
Draw magnetic field lines around a bar magnet.
Answer:
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Intext Questions Page 228 Q1

Question 2
List the properties of magnetic lines of force.
Answer:
Properties of magnetic lines of force :

  • The magnetic field lines originate from the north pole of a magnet and end at its south pole.
  • The magnetic field lines become closer to each other near the poles of a magnet but they are widely separated at other places.
  • Two magnetic field lines do not intersect one another.

Question 3
Why don’t two magnetic lines of force intersect each other ?
Answer:
This is due to the fact that the resultant force on a north pole at any point can be only in one direction. But if the two magnetic field lines intersect one another, then the resultant force on north pole placed at the point of intersection will be along two directions, which is not possible.

Page Number: 229 – 230

Question 1
Consider a circular loop of wire lying on the plane of the table. Let the current pass through the loop clockwise. Apply the right hand rule to find out the direction of the magnetic field inside and outside the loop.
Answer:
As shown in figure alongside, each section of wire produces its concentric set of lines of force. By applying right hand thumb rule, we find that all the sections produce magnetic field downwards at all points inside the loop while at the outside points, the field is directed upwards. Therefore, the magnetic field acts normally into the plane of the paper at the points inside the loop and normally out of the plane of paper at points outside the loop.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Intext Questions Page 229 Q1

Question 2
The magnetic field in a given region is uniform. Draw a diagram to represent it. [CBSE 2013, 2014]
Answer:
A uniform magnetic field in a region is represented by drawing parallel straight lines, ail pointing in the same direction.
For example, the uniform magnetic field which exists inside a current-carrying solenoid can be represented by parallel straight lines pointing from its S-pole to N-pole (as shown in figure).
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Intext Questions Page 229 Q2

Question 3
Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(i) is zero
(ii) decreases as we move towards its end
(iii) increases as we move towards its end
(iv) is the same at all points
Answer:
(iv) Is the same at all points.

Page Number: 231 – 232

Question 1
Which of the following property of a proton can change while it moves freely in a magnetic field. (There may be more than one correct answer.)
(i) Mass
(ii) Speed
(iii) Velocity
(iv) Momentum
Answer:
The correct options are (iii) velocity, (iv) momentum.

Question 2
In Activity 13.7 how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased ?
Answer:
(i) When the current in the rod AB is increased, force exerted on the conductor increases, so the displacement of the rod increases.
(ii) When a stronger horse-shoe magnet is used, the magnitude of the magnetic field increases. This increases the force exerted on the rod and the displacement of the rod.
(iii) When the length of the rod AB is increased, force exerted on the conductor increases, so the displacement of the rod increases.

Question 3
A positively-charged particle (alpha particle) projected towards west is deflected towards north by a magnetic field.
The direction of magnetic field is :
(i) towards south
(ii) towards east
(iii) downward
(iv) upward
Answer:
(iv) Upward.
Here, the positively charged alpha particles are moving towards west, so the direction of current is towards east. The deflection is towards north, so the force is towards north, so, we are given that
(i) direction of current is towards west
(ii) direction of force is towards north.
Let us now hold the forefinger, middle finger and thumb of our left-hand at right angles to one another. Adjust the hand in such a way that our mid finger points towards west (in the direction of current) and thumb points towards north (in the direction of force). Now, if we look at our forefinger, it will be pointing upward. Because the direction of forefinger gives the direction of magnetic field, therefore, the magnetic field is in the upward direction.

Page Number: 233

Question 1
State Fleming’s left hand rule. [CBSE 2018]
Answer:
Fleming’s left hand rule : Stretch the first finger, the middle finger and the thumb of your left hand mutually perpendicular to each other in such a way that the first finger represents the direction of the magnetic field, the middle finger represents the direction of the current in the conductor, then the thumb will represent the direction of motion of the conductor.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Intext Questions Page 233 Q1

Question 2
What is the principle of an electric motor ? [CBSE 2018]
Answer:
A motor works on the principle of magnetic effect of current. When a rectangular coil is placed in a magnetic field and current is passed through it, a force acts on the coil which rotates it continuously.
When the coil rotates, the shaft attached to it also rotates. In this way the electrical energy supplied to the motor is converted into the mechanical energy of rotation.

Question 3
What is the role of the split ring in an electric motor ?
Answer:
The split ring reverses the direction of current in the armature coil after every half rotation, i.e., it acts as a commutator. The reversed current reverses the direction of the forces acting on the two arms of the armature after every half rotation. This allows the armature coil to rotate continuously in the same direction.

Page Number: 236

Question 1
Explain different ways to induce current in a coil.
Answer:
Different ways to induce current in a coil are :

  1. moving a magnet towards or away from the coil or vice-versa, and
  2. changing current in the neighbouring coil.

Page Number: 237

Question 1
State the principle of an electric generator.
Answer:
The electric generator works on the principle that when a straight conductor is moved in a magnetic field, then current is induced in the conductor.
In an electric generator, a rectangular coil is made to rotate rapidly in the magnetic field between the poles of a horse-shoe type magnet. When the coil rotates, it cuts the magnetic field lines due to which a current is produced in the coil.

Question 2
Name some sources of direct current.
Answer:
Some of the sources of direct current are dry cells, button cells, lead accumulators.

Question 3
Which sources produce alternating current ?
Answer:
Alternating current is produced by AC generators of nuclear power plants, thermal power plants, hydroelectric power stations, etc.

Question 4
Choose the correct option : A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each:
(i) two revolution
(ii) one revolution
(iii) half revolution
(iv) one-fourth revolution
Answer:
(iii) Half revolution.

Page Number: 238

Question 1
Name two safety measures commonly used in electric circuits and appliances.
Answer:
(i) Earthing and
(ii) Electric fuse.

Question 2
An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect ? Explain.
Answer:
The electric oven draws a current given by
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Intext Questions Page 238 Q2
Thus the electric oven draws current much more than the current rating 5 A. That is the circuit is overloaded. Due to excessive current, the fuse wire will blow and the circuit will break.
What precautions should be taken to avoid the overloading of domestic electric circuits ?
To avoid the overloading of domestic electric circuits, the following precautions should be taken :
(i) The wires used in the circuit must be coated with good insulating materials like PVC, etc.
(ii) The circuit must be divided into different sections and a safety fuse must be used in each section.
(iii) High power appliances like air-conditioner, refrigerator, a water heater, etc. should not be used simultaneously.

NCERT Solutions for Class 10 Science Chapter 13 Textbook Chapter End Questions

Question 1
Which of the following correctly describes the magnetic field near a long straight wire ?
(i) the field consists of straight lines perpendicular to the wire
(ii) the field consists of straight lines parallel to the wire
(iii) the field consists of radial lines originating from the wire
(iv) the field consists of concentric circles centred on the wire
Answer:
(iv) The field consists of concentric circles centred on the wire

Question 2
The phenomenon of electromagnetic induction is
(i) the process of charging a body
(ii) the process of generating magnetic field due to a current passing through a coil
(iii) producing induced current in a coil due to relative motion between a magnet and the coil
(iv) the process of rotating a coil of an electric motor
Answer:
(iii) Producing induced current in a coil due to relative motion between a magnet and the coil

Question 3
The device used for producing electric current is called a
(i) generator
(ii) galvanometer
(iii) ammeter
(iv) motor
Answer:
(i) Generator.

Question 4
The essential difference between an AC generator and a DC generator is that
(i) AC generator has an electromagnet while a DC generator has permanent magnet
(ii) DC generator will generate a higher voltage
(iii) AC generator will generate a higher voltage
(iv) AC generator has slip rings while the DC generator has a commutator
Answer:
(iv) AC generator has slip rings while the DC generator has a commutator

Question 5
At the time of short circuit, the current in the circuit
(i) reduces substantially
(ii) does not change
(iii) increases heavily
(iv) varies continuously
Answer:
(iii) Increases heavily.

Question 6
State whether the following statements are True or False.
(i) An electric motor converts mechanical energy into electrical energy.
(ii) An electric generator works on the principle of electromagnetic induction.
(iii) The field at the centre a long circular coil carrying current will be parallel straight lines.
(iv) A wire with a green insulation is usually the live wire of an electric supply.
Answer:
(i) False
(ii) True
(iii) True
(iv) False.

Question 7
List three sources of magnetic fields.
Answer:
(i) Current carrying conductor
(ii) Electromagnets
(iii) Permanent magnets

Question 8
How docs a solenoid behave like a magnet ? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
Answer:
A solenoid behaves like a magnet in the following ways.

  • The magnetic field produced by a current carrying solenoid is very much similar to that of a bar magnet.
  • Like a bar magnet, one end of the solenoid has N-polarity while the other end has S-polarity.

To determine the north and south poles, we bring N-pole of the bar magnet near one end of the solenoid. If there is an attraction, then that end of the solenoid has south polarity and the other has north polarity. If there is a repulsion, then that end of the solenoid has north polarity and the other end has south polarity because similar poles repel each other.

Question 9
When is the force experienced by a current-carrying conductor placed in a magnetic field largest ?
Answer:
When the conductor carries current in a direction perpendicular to the direction of the magnetic field, the force experienced by the conductor is largest.

Question 10
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field ?
Answer:
Here the electron beam is moving from our back wall to the front wall, so the direction of current will be in the opposite direction, from front wall towards back wall or towards us. The direction of deflection (or force) is towards our right side.
We now know two things :

  • direction of current is from front towards us, and
  • direction of force is towards our right side.

Let us now hold the forefinger, middle finger and thumb of our left hand at right angles to one another. We now adjust the hand in such a way that our centre finger points towards us (in the direction of current) and thumb points towards right side (in the direction of force). Now, if we look at our forefinger, it will be pointing vertically downwards. Since the direction of forefinger gives the direction of magnetic field, therefore, the magnetic field is in the vertically downward direction.

Question 11
Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor ?
Answer:
Electric Motor : The device used to convert electrical energy to mechanical energy is called Electric Motor. It is used in fans, machines, etc.
Principle : NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric CurrentElectric motor works on the principle of force experienced by a current carrying conductor in a magnetic field. The two forces in the opposite sides are equal and opposite. Since they act in different lines they bring rotational motion.

Working of an electric motor :
When current starts to flow, the coil ABCD is in horizontal position. The direction of current through armature coil has the direction from A to B in the arm AB and from C to D in the arm CD. The direction of force exerted on the coil can be found through Fleming’s left hand law.
According to this law, it is found that the force exerted on the part AB, pushes the coil downwards. While the force exerted on the part CD pushes it upwards. In this way, these two forces being equal and opposite form a couple that rotates the coil in anticlockwise direction.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Chapter End Questions Q11
When the coil is in vertical position, the brushes X and Y would touch the centre of the commutator and the current in the coil is stopped. Though current is stopped but the coil comes back in horizontal state due to momentum.

After half rotation, the polarity of the commutator also changes, because now Q makes contact with brush X and P with brush Y. Therefore, now the force exerts downwards on the arm AB and upwards on the arm CD and thus again a couple of forces is formed that rotates the coil in clockwise direction. This process is repeated again and again and the coil rotates til! the current flows across it.
Function of split ring : Split ring in a motor acts as a commutator, i.e., it reverses the flow of current in the circuit due to which the direction of the forces acting on the arms also reverses.

Question 12
Name some devices in which electric motors are used.
Answer:
Electric motor is used in the appliances like electric fans, washing machine, mixers, grinders, blenders, computers, MP3 players, etc.

Question 13
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (t) pushed into the coil (ii) withdrawn from inside the coil (iii) held stationary inside the coil ? [CBSE (Delhi) 2017, AICBSE 2016]
Answer:
(i) As a bar magnet is pushed into the coil, a momentary deflection is observed in the galvanometer indicating the production of a momentary current in the coil.
(ii) When the bar magnet is withdrawn from the coil, the deflection of galvanometer is in opposite direction showing the production of an opposite current.
(iii) When the bar magnet is held stationary inside the coil, there is no deflection in galvanometer indicating that no current is produced in the coil.

Question 14
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B ? Give reason.
Answer:
Yes, some current will be induced in the coil B. When the current in coil A is changed, some current is induced in the coil B. Due to change in current in coil A, the magnetic field lines linked with coil A and with coil B get changed. This sets up induced current in coil B.

Question 15
State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current (it) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (in) current induced in a coil due to its rotation in a magnetic field.
Answer:
(i) Right hand thumb rule : If the current carrying conductor is held in the right hand such that the thumb points in the direction of the current, then the direction of the curl of the fingers will give the direction of the magnetic field.
(ii) Fleming’s left hand rule : NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Stretch the forefinger, the central finger and the thumb of the left hand mutually perpendicular to each other. If the forefinger points in the direction of the magnetic field, the middle finger in the direction of current, then the thumb points in the direction of force in the conductor.
(iii) Fleming’s right hand rule : Stretch the thumb, forefinger and the central finger of the right hand mutually perpendicular to each other. If the forefinger points in the direction of magnetic field, thumb in the direction of motion of the conductor, then the middle finger points in the direction of current induced in the conductor.

Question 16
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes ?
Answer:
Principle : The electric generator is based on the principle of electromagnetic induction. When a coil is rotated with respect to a magnetic field, the number of magnetic field lines through the coil changes. Due to this a current is induced in the coil whose direction can be found by Fleming’s right hand rule.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Chapter End Questions Q16

Working : When the armature coil ABCD rotates in a magnetic field produced by the permanent magnets, it cuts through the magnetic lines of force.
Due to the rotation of armature coil, the associated magnetic field changes and an induced electromagnetic force is produced in it. The direction of this induced electromotive force or current can be determined by using Fleming’s right hand rule.
In first half cycle the current flows in one direction by brush B1 and in second it flows in opposite direction by brush B2. This process continues. So the current produced is alternating in nature.
Functions of Brushes : Brushes in contact with rings provide the current for external use.

Question 17
When does an electric short circuit occur ?
Answer:
In a domestic circuit, short-circuit occurs when live and neutral wire come in direct contact with each other without any resistance. The resistance of the circuit becomes zero and excessive current starts to flow through it.

Question 18
What is the function of an earth wire ? Why is it necessary to earth metallic appliances ?
Answer:
Earth wire is a safety measure that provides a low resistance conducting path to the current. Sometimes due to excess heat or wear and tear, the live wire comes in direct contact with the metallic cover of the appliances, which can give an electric shock on touching them. To prevent from the shock the metallic part is connected to the earth through a three-pin plug due to which the current flows to the earth at the instant there is a short circuit.

It is necessary to earth metallic appliances because it ensures that if there is any current leakage in the metallic cover, the potential of the appliance becomes equal to that of the earth. The potential of the earth is zero. As a result, the person handling the appliance will not get an electric shock.

NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current

Magnetic effects of current: Magnetic field, field lines, field due to a current carrying conductor, field due to current carrying coil or solenoid; Force on current carrying conductor, Fleming’s left hand rule. Electromagnetic induction, Induced potential difference, Induced current, Fleming’s right hand rule, Direct current, Alternating current, frequency of AC, Advantage of AC over DC, Domestic electric circuits.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 13
Chapter NameMagnetic Effects of Electric Current
Number of Questions Solved39
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Question 1
Why does a compass needle gets deflected when brought near a bar magnet?
Solution:
A compass needle is, in fact, a small bar magnet. If this is brought near another bar magnet, the like poles repel and the needle gets deflected.

Question 2
Draw magnetic field lines around a bar magnet?
Solution:
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Q2

More Resources for CBSE Class 10

Question 3
List the properties of magnetic lines of force.
Solution:
a) Magnetic lines are directed from the north pole towards the south pole.
b) They do not cross each other.
c) They are more crowded near the poles than at any other region in the field.
d) They are closed curves.
e) In the uniform magnetic field, the lines of force are parallel to one another.

Download NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current PDF

Question 4
Why don’t two magnetic lines of force intersect each other?
Solution:
No two field-lines are found to cross each other. If they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.

Question 5
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the magnetic field inside and outside the loop.
Solution:
At every point of a current –carrying loop, the concentric circles representing the magnetic field around it would become larger and larger as we move away from the wire. By the time we reach at the center of the circular loop, the arc of these big circles would appear as straight lines.

Question 6
The magnetic field in a given region is uniform. Draw a diagram to represent it.
Solution:
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Q6

Question 7
The magnetic field inside a long straight solenoid-carrying current
a) is zero
b) decreases as we move towards its end
c) increases as we move towards its end
d) is the same at all points
Solution:
d) is the same at all points

Question 8
Which of the following property of a proton can change while it moves freely in a magnetic field?
a) Mass
b) Speed
c) Velocity
d) Momentum
Solution:
c) Velocity
d) Momentum.

Question 9
(a) Current in rod AB is increased?
(b) A stronger horseshoe magnet is used?
(c) Length of the rod AB is increased?
Solution:
(a) If the current in rod AB is increased, the displacement of rod AB will not be affected.
(b) If a stronger horseshoe magnet is used, force is exerted and hence the displacement increases.
(c) If the length of the rod AB is increased there is no change in the displacement of the rod AB.

Question 10
A positively-charged particle projected towards west is deflected towards north by a magnetic field. The direction of the magnetic field is
a) Towards south
b) Towards east
c) Downward
d) Upward
Solution:
b) Towards east.

Question 11
State Fleming’s left-hand rule.
Solution:
Fleming’s left-hand rule states that, stretch the thumb, fore finger and middle finger of the left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.

Question 12
What is the principle of an electric motor?
Solution:
Principle of an electric motor:
The working of the electric motor is based on the mechanical effect of an electric current. A conductor carrying a current placed in a magnetic field experiences a mechanical force.
In the motor, when a current is passed through a rectangular coil of wire placed in a magnetic field, the coil rotates continuously.

Question 13
What is the role of the split ring in an electric motor?
Solution:
In electric motor, the split ring acts as a commutator. A device that reverses the direction of flow of current through a circuit is called a commutator. The reversal of current also reverses the direction of force acting on the two arms AB and CD.

Question 14
Explain different ways to induce current in a coil.
Solution:
Current can be induced in a coil either by moving it in a magnetic field or by changing the magnetic field around it. The induced current is found to be the highest when the direction of motion of the coil is at right angles to the magnetic field. The process, by which a changing magnetic field in a conductor induces a current in another conductor, is called electromagnetic induction.

Question 15
State the principle of an electric generator.
Solution:
A generator is also known as a dynamo. It is a device used to convert mechanical energy in to electrical energy. The mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. It is an application of electromagnetic induction.
An A.C generator generates an alternating current.
A D.C generator is used to deliver a current, which flows in the same direction.

Question 16
Name some source of direct current.
Solution:
The source of direct current is a split-ring type commutator, one brush is at all times in contact with the arm moving up in the field, while the other is in contact with the arm moving down. Thus a unidirectional current is produced.

Question 17
Which sources produce alternating current?
Solution:
The sources which produce alternating current is a permanent magnet called the field magnet, armature, slip ring and carbon brushes. After every half rotation the polarity of the current in the respective arms changes. Such a current, Which changes direction after equal intervals of time, is called an alternating current.

Question 18
A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each:
a) Two revolutions
b) One revolution
c) Half revolutions
d) One-fourth revolutions.
Solution:
b) One revolution.

Question 19
Name two safety measures commonly used in electric circuits and appliances.
Solution:
The use of an electric fuse prevents the electric circuits and appliance from a possible damage by passing the flow of unduly high electric current. The Joule heating that takes place in the fuse melts it to break the electric circuit.

Question 20
An electric oven of 2 KW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
Solution:
V = 220 V, I = 5 A
Power, P = VI
P = 220 × 5
P = 1100 W
Therefore, power P = 1100 W = 1.1 KW
Therefore, an electric oven of 2 KW power rating cannot be operated in a domestic electric circuit (220 V) that has a current rating of 5 A because electric oven has higher power than the power of the electric circuit.

Question 21
What precaution should be taken to avoid the overloading of domestic electric circuits?
Solution:
Fuse is the most important safety device, to avoid the overloading of domestic electric circuits.
Too many appliances should not be connected to a single socket.

Question 22
Which of the following correctly describes the magnetic field near a long
straight wire?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.
Solution:
(d) The field consists of concentric circles centred on the wire.

Question 23
The phenomenon of electromagnetic induction is
(a) the process of charging a body.
(b) the process of generating magnetic field due to a current passing through a coil.
(c) producing induced current in a coil due to relative motion between a magnet and the coil.
(d) the process of rotating a coil of an electric motor.
Solution:
(c) producing induced current in a coil due to relative motion between a magnet and the coil.

Question 24
The device used for producing electric current is called a
(a) generator.
(b) galvanometer.
(c) ammeter.
(d) motor.
Solution:
(a) generator.

Question 25
The essential difference between an AC generator and a DC generator is that:
(a) AC generator has an electromagnet while a DC generator has permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator
Solution:
(d) AC generator has slip rings while the DC generator has a commutator.

Question 26
At the time of short circuit, the current in the circuit
(a) reduces substantially.
(b) does not change.
(c) increases heavily.
(d) vary continuously.
Solution:
(c) increases heavily.

Question 27
State whether the following statements are true or false.
Solution:
(a) An electric motor converts mechanical energy into electrical energy – false.
(b) An electric generator works on the principle of electromagnetic induction – true
(c) The field at the centre of a long circular coil carrying current will be parallel straight lines – true.
(d) A wire with a green insulation is usually the live wire of an electric supply – true.

Question 28
List three sources of magnetic fields.
Solution:
a) Magnetic field due to a current through a straight conductor.
b) Magnetic field due to a current in a solenoid.
c) Magnetic field due to a current through a circular loop.

Question 29
How does a solenoid behave like a magnet? Can you determine the north and the south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
Solution:
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Q29
A coil of many circular turns of insulated copper wire wrapped closely in the shape of the cylinder is called a solenoid. The pattern of the magnetic field lines around a current- carrying solenoid is shown in this figure. In fact, one end of the solenoid behaves as a magnetic north pole, while the other behaves as the south pole. The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.
A strong magnetic field produced inside a solenoid can be used to magnetise a piece of magnetic material, like soft iron, when placed inside the coil. The magnet so formed is called an electromagnet.

Question 30
When is the force experienced by a current-carrying conductor placed in a magnetic field the largest?
Solution:
The force experienced by a current-carrying conductor placed in a magnetic field is largest provided when the direction of current is at right angles to the direction of the magnetic field.

Question 31
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
Solution:
The direction of magnetic field is towards west.

Question 32
Draw a labelled diagram of an electric motor. Explain its principle and working.What is the function of a split ring in an electric motor?
Solution:
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Q32
A motor is a device that converts the electrical energy into mechanical energy.
Principle
An electric motor is based on the fact that when a current carrying conductor is placed in a magnetic field the conductor experiences a force which is given by Fleming’s Left Hand Rule. For example, when a rectangular coil is placed in the magnetic field and current is passed through it, a torque acts on the coil, which rotates it continuously. When the coil rotates, the shaft attached to it also rotates and therefore the electrical energy supplied to the motor is converted into the mechanical energy of rotation.

An electrical motor consists of a rectangular coil ABCD of insulated copper wire, wound on a soft iron core called armature. The coil is mounted between the poles of a magnet in such a way that it can rotate between the poles N and S. The two ends of the coil are soldered to the ends of a commutator whose main function is to reverse the direction of the current flowing through the coil every time the coil just passes the vertical position during its revolution.

Working
Suppose the coil ABCD is initially at a horizontal position. When the switch is in ON position the current enters the coil through the carbon brushes and the half ring ‘A’ of the commutator.

The current flows in the direction DCBA and leaves via the half ring ‘B’. In the side PQ of the coil, the direction is from Q to P towards the south and the direction of the magnetic field is from the N to S pole towards the east. So, by applying Fleming’s left hand rule, we find that it will experience a force in upward direction. Similarly, the side SR of the coil will experience a downward force. Thus we have two parallel wires experiencing forces in opposite directions. They form a couple tending to rotate the coil in the anticlockwise direction.

When the coil goes beyond the vertical position, the two commutator half rings automatically changes contact from one brush to the other. This reverses the direction of current through the coil which, in turn, reverses the direction of forces acting on the two sides of the coil. The sides of the coil are interchanged, but rotate in the same anticlockwise direction. This process is repeated again and again and the coil continues to rotate as long as the current is passing.

Question 33
Name some devices in which electric motors are used.
Solution:
Electric fans, refrigerators, mixers, washing machines, computers, MP3 players etc are some devices in which electric motors are used.

Question 34
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is
(i) pushed into the coil,
(ii) withdrawn from inside the coil,
(iii) held stationary inside the coil?
Solution:
(i) A deflection is observed in the galvanometer due to the induced current because of the changing magnetic flux (increasing) through the turns of the coil connected to the galvanometer.
(ii) A deflection is again observed in the galvanometer, as when it is pulled out, the flux linked with the coil due to the bar magnet decreases. Hence a current flows in the coil to reduce the change in flux. The deflection can be observed in the opposite direction as compared with the previous case.
(iii) No deflection is observed in the galvanometer. The flux linked with the coil due to the magnetic field is at a constant. Hence no current is induced due to the bar magnet.

Question 35
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
Solution:
Yes, if the current in the coil A is changed, then some current will be induced in the coil B because due to the change in the magnetic field effect around the coils.

Question 36
State the rule to determine the direction of a
(i) magnetic field produced around a straight conductor-carrying current,
(ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and
(iii) current induced in a coil due to its rotation in a magnetic field.
Solution:
(i) Right-hand thumb rule
Imagine that we are holding a current carrying straight conductor in the right hand such that the thumb points towards the direction of current. Then our fingers will wrap around the conductor in the direction of the field lines of the magnetic field. This is known as Right-hand thumb rule.
(ii) Fleming’s left-hand rule
Fleming’s left-hand rule states that, stretch the thumb, fore finger and middle finger of the left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
(iii) Fleming’s right-hand rule
If the thumb and the first two fingers of right hand are held at right angles to each other, with the Forefinger held in the direction of the field, and the thumb in the direction of motion, the induced current I flows in the direction of the middle finger.

Question 37
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?
Solution:
A C. generator
“A C. generator” means “Alternating Current generator”. That is, an A. C. generator produces alternating current, which alternates (changes) in polarity continuously. We will now describe the construction an working of the A. C. generator or A. C. dynamo.
Construction of an A. C. generator
A simple A. C. generator consists of a rectangular coil ABCD that can be rotated rapidly between the poles N and S of a strong horseshoe type magnet M. The coil is made of a large number of turns of insulated copper wire. The ends A and D of the rectangular coil are connected to two circular pieces of copper metal called slip rings R1 and R2. As the slip rings R1 and R2 rotate with the coil, the two pieces of carbon called brushes, B1 and B2, keep contact with them. So, the current produced in the rotating coil can be tapped out through slip rings into the carbon brushes. From the carbon brushes B1 and B2 we take the current into various electrical appliances like radio, T. V., electric iron, bulbs, etc. But in this figure, we have shown only a galvanometer G connected the two carbon brushes.

Working of an A. C. generator

Suppose that the generator coil ABCD is initially in the horizontal position. Again suppose that he coil ABCD is being rotated in the anticlockwise direction between the poles N and S of a horseshoe type magnet.

(i) As the coil rotates in the anticlockwise direction, the side AB of the coil moves down cutting the magnetic lines of force near the N-pole of the magnet, and side CD moves up, cutting the lines of force near the S-pole of the magnet. Due to this, induced current is produced in the sides AB and DC of the coil. On applying Fleming’s right hand rule to the side AB and DC of the coil, we find that the currents are in the direction B to A and D to C respectively. Thus, the induced currents in the two sides of the coil are in the same direction, and we get an effective induced current in the direction BADC.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Q37.1
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Q37.2

(ii) After half revolution, the sides AB and DC of the coil will interchange their positions. The side AB will come on the right hand side and DC will come on the left side. So, after half a revolution, side AB starts moving up and side DC starts coming down. As a result of this, the direction of induced current in each side of the coil is reversed after half a revolution. Since the direction of induced current in the coil is reversed after half revolution so the polarity (positive and negative) of the two ends of the coil also changes after half revolution. The end of coil which was positive in the first half of rotation becomes negative in the second in the second half. And the end which was negative in the first half revolution becomes positive in the second half of revolution. Thus, in 1 revolution of the coil, the current changes its direction 2 times.

The alternating current (A. C.) produced in India has a frequency of 50 Hz. That is, the coil is rotated at the rate of 50 revolutions per second. Since in 1 revolution of coil, the current changes its direction 2 times, so in 50 revolutions of coil, the current changes its direction 2 × 50 = 100 times. Thus, the A. C. supply in India changes its direction 100 times in 1 second. Another way of saying this is that the alternating current produced in India changes its direction every 1/100 second. That is, each terminal of the coil is positive (+) for 1/100 of a second and negative (-) for the next 1/100 of a second. This process is repeated again and again with the result that there is actually no positive and negative in an A. C. generator. We will now describe why the direction of induced current in the coil of an A. C. generator changes after every half revolution of the coil.

After every half revolution, each side of the generator coil starts moving in the opposite direction in the magnetic field. The side of the coil which was initially moving downwards in a magnetic field, after half revolution, it starts moving in opposite direction – upwards. Similarly the side of coil which was initially moving upwards, after half revolution, it starts moving downwards. Due to the change in the direction of motion of the two sides of the coil in the magnetic field after every half revolution, the direction of current produced in them also changes after every half revolution.

D. C. generator
“D. C. generator” means “Direct Current generator”. That is, a D. C. generator produces direct current and not alternating current. We will now describe the construction and working of D. C. generator or D. C. Dynamo.
Construction of a D. C. generator
A simple D. C. generator consists of a rectangular coil ABCD which cab be rotated rapidly between the poles N and S of a strong horse-shoe type magnet M. The generator coil is made of a large number of turns of insulated copper wire. The two ends of the coil are connected to the two copper half rings (or split rings) R1 and R2 of a commutator. There are two carbon brushes B1 and B2 which press lightly against the two half rings. When the coil is rotated, the two half rings R1 and R2 touch the two carbon brushes B1 and B2 one by one. So the current produced in the rotating coil can be tapped out through the commutator half rings into the carbon brushes. From the carbon brushes B1 and B2, we can take the current into the various electrical appliances like radio, T. V., electric iron, bulbs, etc. But in this figure, we have shown only a galvanometer G connected between the two carbon brushes. The galvanometer is a current detecting and current measuring instrument.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Q37

Working of a D. C. generator
Suppose that the generator coil ABCD is initially in the horizontal position. Again suppose that he coil ABCD is being rotated in the anticlockwise direction between the poles N and S of a horseshoe type magnet.

(iii) As the coil rotates in the anticlockwise direction, the side AB of the coil moves down cutting the magnetic lines of force near the N-pole of the magnet, and side DC moves up, cutting the lines of force near the S-pole of the magnet. Due to this, induced current is produced in the sides AB and DC of the coil. On applying Fleming’s right hand rule to the side AB and DC of the coil we find that the currents in them are in the direction B to A and D to C respectively. Thus, the induced currents in the two sides of the coil are in the same direction, and we get an effective induced current in the direction BADC. Due to this the brush B1 becomes a positive (+) pole and brush B2 becomes negative (-) pole of the generator.

(iv) After half revolution, the sides AB and DC of the coil will interchange their positions. The side AB will come on the right hand side and start moving up whereas side DC will come on then the two commutator half rings R1 and R2 automatically change their contacts from one carbon brush to the other. Due to this change, the current keeps flowing in the same direction in the other circuits. The brush B1 always remaining positive terminal and brush B2 always remaining negative terminal of the generator. Thus, a D. C. generator supplies a current in one direction by the use of a commutator consisting of two, half-rings of copper. In the above discussion we have used the word D. C. generator everywhere. Please note that we can also write D. C. dynamo in place of D. C. generator.

Question 38
When does an electric short circuit occur?
Solution:
Short circuiting
If the plastic insulation of the live wire and neutral wire gets torn, then the two wires touch each other. This touching of the live wire and neutral wire directly is known as short-circuiting. The current passing through the circuit formed by these wires is very large and consequently a high heating effect is created which may lead to fire.

Question 39
What is the function of an earth wire? Why is it necessary to earth metallic appliances?
Solution:
To avoid electric shocks, the metal body of an electrical device is ‘earthed’. A wire called ‘earth wire’ is used to connect the metal body of the electrical device to the earth, which is at zero potential. In household circuits, we have three wires, the live wire, the neutral wire and the earth wire. One end of the earth wire is connected to the device and the other end of the wire is connected to the earth. We now say that the device is “earthed” or “grounded”. Usually the three wires are connected to a three-pin plug. The neutral wire or the earth connection carries the high current to the earth from the device and prevents an electric shock.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
A compass is to be placed near a bar magnet with unknown poles. Outside the magnetic field, the compass needle is pointing towards North as shown below:
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q1
Answer:
(c) Magnetic field lines always point from North pole to South pole around the magnet. Thus, compass needle follows the path difference of magnetic field lines.

Question 2.
A bar magnet is broken into three parts X, Y and Z.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q2
Which diagram show the poles in X, Y and Z?
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q2.1
Answer:
(d) When a magnet is broken into three parts X, Y and Z, each part is still a magnet and the strength of the magnetic force remains the same.

Question 3.
An unmagnetised iron bar is placed near the end of a bar magnet.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q3
Which of the following diagram is correct?
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q3.1
Answer:
(b) The end of the iron bar nearer to the South pole of the bar magnet becomes induced North pole while the other end is South pole.

Question 4.
The diagram shows a current-carrying wire passing through the centre of a square cardboard.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q4
How do the strengths of the magnetic field at points X, Y and Z compare?
(a) equal at X, Y and Z
(b) stronger at Y than X, equal at Y and Z
(c) weaker at Y than Z, stronger at Y than Z
(d) stronger at Y than X, weaker at Z than X
Answer:
(d) The closer to the wire, the stronger is the magnetic field strength. Since, the magnetic field is circular. Y is the closest followed by X than Z.

Question 5.
A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is on.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q5
The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti-clockwise and clockwise, respectively.
The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to
(a) A
(b) B
(c) A if the current is small and B if the current is large
(d) B if the current is small and A if the current is large [NCERT Exemplar]
Answer:
(a) The N-pole of the resultant magnet is on the face close to A because, the magnetic field lines enter in loop from B and come out from A. Also, as a matter of fact magnetic lines come out of the N-pole of magnet. Therefore, face close to A represents N-pole. The currents in A and B are same.

Question 6.
A bar magnet is used to pick up an iron nail.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q6
At which parts X, Y and Z is the easiest for the magnet to pick up the iron nail?
(a) At X
(b) AtY
(c) At Z
(d) It makes no difference
Answer:
(c) The region with the highest density of magnetic field lines has the greatest strength.

Question 7.
If the key in the arrangement as shown below is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are [NCERT Exemplar]
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q7
(a) concentric circles
(b) elliptical in shape
(c) straight lines parallel to each other
(d) concentric circles near the point O but of elliptical shapes as we go away from it
Answer:
(c) When the key is taken out (the circuit is made open), no current flows through the wire, hence no magnetic field exists due to the conductor.
The only magnetic field is due to Earth’s magnetic field and are straight lines parallel to each other. The horizontal component is directed from geographical South to geographical North on the horizontal plane ABCD.

Question 8.
Four metal rods are placed in turn inside the solenoid to attract paper clips.
The table below gives the results of the experiment when current is switched on and off.

MetalrodWhen current is switched on, number of paper clips attractedWhen current is switched off, number of paper clips still attracted
(a)10
(b)202
(c)350
(d)3530

Which rod would be the most suitable to use for the core of the solenoid in a circuit breaker?
Answer:
(c) The core of the solenoid in a circuit breaker must be made of a soft type magnetic material which can be strongly magnetised but does not retain induced magnetism.

Question 9.
Permanent magnets can be made using hard magnetic materials.
Which of the following is not the correct method to make permanent magnets?
(a) Using a bar magnet to stroke a steel bar
(b) Using two bar magnets to stroke a steel bar
(c) Placing a steel bar in a solenoid that connects to a DC supply
(d) Placing a steel bar in a solenoid that connects to an AC supply, then slowly withdrawing the steel bar away from the solenoid in West-East direction
Answer:
(d) The AC supply will mix up the direction of the magnetic domains. In fact, this is one of the methods to demagnetise magnets.

Question 10.
In the arrangement shown in figure, there are two coils wound on a non-conducting cylindrical rod. Initially, the key is not inserted. Then, the key is inserted and later removed. Then,
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current MCQs Q10
(a) the deflection in the galvanometer remains zero throughout.
(b) there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed.
(c) there are momentary galvanometer deflections that die out shortly, the deflections are in the same direction.
(d) there are momentary galvanometer deflections that die out shortly, the deflections are in opposite directions. Thus, the galvanometer shows momentary deflections in opposite directions. [NCERT Exemplar]
Answer:
(d) In the given arrangement, whenever an electric current through the first coil is changed, an emf is induced in the coil due to change in magnetic field lines which pass through the neighbouring second coil. When key is inserted and removed, then the magnetic field lines passing through second coil increases and decreases in two cases respectively. Therefore, the direction of current in two cases is opposite. Thus, the galvanometer shows momentary deflections in opposite directions.

NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current (Hindi Medium)

NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Hindi Medium 1
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NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Hindi Medium 10
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Class 10 Science Magnetic Effects of Electric Current Mind Map

Properties of Magnets

  • Attractive property: Magnets attract magnetic materials like – iron, cobalt, nickel, etc
  • Directive property: A freely suspended magnet always aligns in north- south direction
  • Opposite poles attract and like poles repel.
  • Poles exist in pairs North and South
  • Repulsion is a sure test of magnet

Magnetic Field
Space around a magnet in which magnetic effect is experienced

Magnetic Field Lines
A line such that the tangent at any point on it gives the direction of the magnetic field at that point.

Properties of Magnetic Field Lines

  • All field lines are closed curves.
  • Field lines are close together near the poles.
  • Two field lines never intersect each other.

Magnetic Field Due to a Current Carrying Conductor
The magnetic field around a straight conductor carrying current is in the form of closed circular loops, in a plane perpendicular to the conductor.
Direction of magnetic field can be determined by using Right hand thumb rule
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Mind Map 1

Solenoid
A solenoid is a long cylindrical helix, which produces a magnetic field when an electric current is passed through it.

The magnetic field within the solenoid is uniform and parallel to the axis of solenoid.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Mind Map 2

The magnetic field due to solenoid depends upon
(a) number of turns i.e., B ∝ n
(b) strength of current i.e, B ∝ I
(c) Nature of material inside solenoid i.e., B ∝ μ

Magnetic Field Due to a Circular Current Carrying Loop
At every’ point of a current carrying loop, the concentric circles representing the magnetic field around it would become larger as we move away.
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Mind Map 3
Direction of magnetic field can be determined by using right hand rule

Force on a Current Carrying Conductor
The force experienced by the conductor
F→=IL×B→
Direction of force can be determined by Fleming’s left hand rule, right hand palm or screw rule
NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Mind Map 4

Electromagnet
A solenoid with a soft iron core. A magnetic field is produced then an electric current flows through a coil of wire.
Uses

  • For lifting and transporting large masses of iron scrap.
  • For loading furnaces with iron.
  • Electric bell, telegraph, electric motor, relay, loud speaker, microphone
  • For separating magnetic substances such as iron from other debris
  • In scientific research to study the magnetic properties of a substance in a magnetic field

Electric Motor
It converts electrical energy to mechanical energy.
It works on the principle of electromagnetic induction

Parts of Electric Motor

  • Armature
  • Field magnet
  • Split-ring
  • Commutator converts alternating voltage into direct voltage across the brushes.
  • Brushes
  • Battery

Uses

  • The d.c. motors are used in d.c. fans
  • They are used for pumping water
  • Big d.c. motors are used for running tramcars and even trains

Electric Generator

  • It converts mechanical energy to electrical energy.
  • It works on the principle of electromagnetic induction

Parts of Electric Generator

  • Armature
  • Magnet
  • Slip-rings
  • Brushes
  • Split ring type commutator for direct current generator
    NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Mind Map 5

Types of Electric Generator
D.C. Generator
It is a type of generator which is used to produce induced current which flows in one direction

A.C. Generator
It generates alternating current that changes its polarity after every half rotation

Electromagnetic Induction
Voltage is induced by the relative motion between a wire and a magnetic field.
The amount of voltage induced depends on how fast the magnetic field lines are entering or leaving the coil.

Safety Devices

  • When too much current flows or short circuit these devices breaks the circuit.
  • They have less melting point.
  • Fuses
  • Miniature circuit breakers (MCBs)

Now that you are provided all the necessary information regarding NCERT Solutions For Class 10 Science Chapter 13 Magnetic Effects Of Electric Current and we hope this detailed article on magnetic effect of electric current class 12 ncert solutions is helpful. If you have any query regarding this article or magnetic effect of electric current class 10 ncert solutions, ping us through the comment section below and we will get back to you as soon as possible.

NCERT Solutions for Class 10 Science Chapter 12 Electricity

NCERT Solutions For Class 10 Science Chapter 12 Electricity: In this article, we will provide you all the necessary information regarding NCERT solutions for class 10 science physics chapter 12 electricity. Working on CBSE class 10 physics electricity questions and answers will help candidates to score good marks in-class tests as well as in the CBSE Class 10 board exam.

Electricity class 10 NCERT solutions will not only help in board exam preparation but also helps in clearing the competitive exams like Engineering. Also, candidates can find electricity class 10 numericals with solutions which helps candidates solving their assignments. Read on to find out everything NCERT Solutions For Class 10 Science Chapter 12 Electricity.

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 12 Electricity, let’s have an overview of the list of topics and subtopics under Electricity class 10 NCERT solutions:

  1. Electricity
  2. Electric Current And Circuit
  3. Electric Potential And Potential Difference
  4. Circuit Diagram
  5. Ohm’S Law
  6. Factors On Which The Resistance Of A Conductor Depends
  7. Resistance Of A System Of Resistors
  8. Heating Effect Of Electric Current
  9. Electric Power

Free download NCERT Solutions for Class 10 Science Chapter 12 Electricity PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 12 Intext Questions

Page Number: 200

Question 1
What does an electric circuit mean ?
Answer:
A continuous and closed path along which an electric current flows is called an electric circuit.

Question 2
Define the unit of current.
Answer:
Unit of current is ampere. If one coulomb of charge flows through any section of a conductor in one second then the current through it is said to be one ampere.
I = Qt or 1 A = I C s-1

Question 3
Calculate the number of electrons constituting one coulomb of charge.
Answer:
Charge on one electron, e = 1.6 x 10-19 C
Total charge, Q = 1 C
Number of electrons, n = Qe = 1C1.6×10−19 = 6.25 x 1018

Page Number: 202

Question 1
Name a device that helps to maintain a potential difference across a conductor.
Answer:
A battery.

Question 2
What is meant by saying that the potential difference between two points is IV?
Answer:
The potential difference between two points is said to be 1 volt if 1 joule of work is done in moving 1 coulomb of electric charge from one point to the other.

Question 3
How much energy is given to each coulomb of charge passing through a 6 V battery ?
Answer:
Energy given by battery = charge x potential difference
or W = QV = 1C X 6V = 6J.

Page Number: 209

Question 1
On what factors does the resistance of a conductor depend ?
OR
List the factors on which the resistance of a conductor in the shape of a wire depends. [CBSE2018]
Answer:
The resistance of a conductor depends (i) on its length (ii) on its area of cross-section and (iii) on the nature of its material.

Question 2
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source ? Why ?
Answer:
The current will flow more easily through a thick wire than a thin wire of the same material. Larger the area of cross-section of a conductor, more is the ease with which the electrons can move through the conductor. Therefore, smaller is the resistance of the conductor.

Question 3
Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it ?
Answer:
When potential difference is halved, the current through the component also decreases to half of its initial value. This is according to ohm’s law i.e., V ∝ I.

Question 4
Why are coils of electric toasters and electric irons are made of an-alloy rather than a pure metal ?
OR
Why are alloys commonly used in electric heating devices? Given reason. [CBSE 2018]
Answer:
The coils of electric toasters, electric irons and other heating devices are made of an alloy rather than a pure metal because (i) the resistivity of an alloy is much higher than that of a pure metal, and (ii) an alloy does not undergo oxidation (or burn) easily even at high temperature, when it is red hot.

Question 5
Use the data in Table 12.2 (in NCERT Book on Page No. 207) to answer the following :
(i) Which among iron and mercury is a better conductor ?
(ii) Which material is the best conductor ?
Answer:
(i) Resistivity of iron = 10.0 x 10-8 Ω m
Resistivity of mercury = 94.0 x 10-8 Ω m.
Thus iron is a better conductor because it has lower resistivity than mercury.
(ii) Because silver has the lowest resistivity (= 1.60 x 10-8 Ω m), therefore silver is the best conductor.

Page Number: 213

Question 1
Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5Ω resistor, an 8 Ω resistor, and a 12 Ω resistor, and a plug key, all connected in series.
Answer:
The required circuit diagram is shown below :
NCERT Solutions for Class 10 Science Chapter 12 Electricity Intext Questions Page 213 Q1

Question 2
Redraw the circuit of Questions 1, putting in an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the 12 Ω resistor. What would be the readings in the ammeter and the voltmeter ?
Solution:
The required circuit diagram is shown on the right.
Total voltage, V = 3 x 2 = 6V
Total resistance, R = 5Ω + 8Ω + 12Ω = 25Ω
NCERT Solutions for Class 10 Science Chapter 12 Electricity Intext Questions Page 213 Q2
NCERT Solutions for Class 10 Science Chapter 12 Electricity Intext Questions Page 213 Q2.1

Page Number: 216

Question 1
Judge the equivalent resistance when the following are connected in parallel :
(i) 1 Ω and 106 Ω,
(if) 1 Ω and 103 Ω and 106 Ω.
Answer:
When the resistances are connected in parallel, the equivalent resistance is smaller than the smallest individual resistance.
(i) Equivalent resistance < 1 Ω.
(ii) Equivalent resistance < 1 Ω.

Question 2
An electric lamp of 100 Ω, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it ?
Solution:
Resistance of electric lamp, R1 = 100 Ω
Resistance of toaster, R2 = 50 Ω
Resistance of water filter, R3 = 500 Ω
Equivalent resistance Rp of the three appliances connected in parallel, is
NCERT Solutions for Class 10 Science Chapter 12 Electricity Intext Questions Page 216 Q2
Resistance of electric iron = Equivalent resistance of the three appliances connected in parallel = 31.25 Ω
Applied voltage, V = 220 V
Current, I = VR = 220V31.25Ω

Question 3
What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series ?
Answer:
Advantages of connecting electrical devices in parallel with the battery are :

  1. In parallel circuits, if an electrical appliance stops working due to some defect, then all other appliances keep working normally.
  2. In parallel circuits, each electrical appliance has its own switch due to which it can be turned on turned off independently, without affecting other appliances.
  3. In parallel circuits, each electrical appliance gets the same voltage (220 V) as that of the power supply line.
  4. In the parallel connection of electrical appliances, the overall resistance of the household circuit is reduced due to which the current from the power supply is high.

Question 4
How can three resistors of resistances 2Ω, 3 Ω, and 6Ω be connected to give a total resistance of (i) 4 Ω, (ii) 1 Ω ?
Solution:
(i) We can get a total resistance of 4Ω by connecting the 2Ω resistance in series with the parallel combination of 3Ω and 6Ω.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Intext Questions Page 216 Q4
(ii) We can obtain a total resistance of 1Ω by connecting resistors of 2 Ω, 3 Ω and 6 Ω in parallel.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Intext Questions Page 216 Q4.1

Question 5
What is (i) the highest, (ii) the lowest total resistance that can be secured by combinations of four coils of resistance 4 Ω, 8 Ω, 12 Ω, 24 Ω?
Solution:
(i) Highest resistance can be obtained by connecting the four coils in series.
Then, R = 4Ω + 8Ω + 12Ω + 24Ω = 48Ω
(ii) Lowest resistance can be obtained by connecting the four coils in parallel.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Intext Questions Page 216 Q5

Page Number: 218

Question 1
Why does the cord of an electric heater not glow while the heating element does ?
Solution:
Heat generated in a circuit is given by I2R t. The heating element of an electric heater made of nichrome glows because it becomes red-hot due to the large amount of heat produced on passing current because of its high resistance, but the cord of the electric heater made of copper does not glow because negligible heat is produced in it by passing current because of its extremely low resistance.

Question 2
Compute the heat generated while transferring 96000 coulomb of charge in one hour through a potential difference of 50 V.
Solution:
Here, Q = 96,000 C, t =1 hour = 1 x 60 x 60 sec = 3,600 s, V = 50 V
Heat generated, H = VQ = 50Vx 96,000 C = 48,00,000 J = 4.8 x 106 J

Question 3
An electric iron of resistance 20Ω takes a current of 5 A. Calculate the heat developed in 30 s.
Solution:
Here, R = 20 Ω, i = 5 A, t = 3s
Heat developed, H = I2 R t = 25 x 20 x 30 = 15,000 J = 1.5 x 104 J

Page Number: 220

Question 1
What determines the rate at which energy is delivered by a current ?
Answer:
Resistance of the circuit determines the rate at which energy is delivered by a current.

Question 2
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
Answer:
Here, I = 5 A, V = 220 V, t = 2h = 7,200 s
Power, P = V I = 220 x 5 = 1100 W
Energy consumed = P x t = 100 W x 7200 s = 7,20,000 J = 7.2 x 105 J

NCERT Solutions for Class 10 Science Chapter 12 Textbook Chapter End Questions

Question 1
A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R’, then the ratio R/R’ is :
(a) 125
(b) 15
(c) 5
(d) 25
Answer:
(d) 25

Question 2
Which of the following terms does not represent electrical power in a circuit?
(a) I2R
(b) IR2
(c) VI
(d) v22
Answer:
(fa) IR2

Question 3
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be :
(a) 100 W
(b) 75 W
(c) 50 W
(d) 25 W
Answer:
(d) 25 W

Question 4
Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be :
(a) 1 : 2
(b) 2 : 1
(c) 1 : 4
(d) 4 : 1
Answer:
(c) 1 : 4

Question 5
How is a voltmeter connected in the circuit to measure the potential difference between two points ?
Answer:
A voltmeter is connected in parallel to measure the potential difference between two points.

Question 6
A copper wire has diameter 0.5 mm and resistivity of 1.6 x 10-8 Ω m. What will be the length of this wire to make its resistance 10 Ω ? How much does the resistance change if the diameter is doubled ?
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q6
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q6.1
If a wire of diameter doubled to it is taken, then area of cross-section becomes four times.
New resistance = 102 = 2.5 Ω, Thus the new resistance will be 14 times.
Decrease in resistance = (10 – 2.5) Ω = 7.5 Ω

Question 7
The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below :
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q7
Plot a graph between V and I and calculate the resistance of the resistor.
Solution:
The graph between V and I for the above data is given below.
The slope of the graph will give the value of resistance.
Let us consider two points P and Q on the graph.
and from P along Y-axis, which meet at point R.
Now, QR = 10.2V – 34V = 6.8V
And PR = 3 – 1 = 2 ampere
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q7.1
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q7.2
Thus, resistance, R = 3.4 Ω

Question 8
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Solution:
Here, V = 12 V and I = 2.5 mA = 2.5 x 10-3 A
∴ Resistance, R = VI = 12V2.5×103A = 4,800 Ω = 4.8 x 10-3 Ω

Question 9
A battery of 9V is connected in series with resistors of 0.2 O, 0.3 O, 0.4 Q, 0.5 Q and 12 £1, respectively. How much current would flow through the 12 Q resistor?
Solution:
Total resistance, R = 0.2 Ω + 0.3 Ω + 0.4 Ω + 0.5 Ω + 12 Ω – 13.4 Ω
Potential difference, V = 9 V
Current through the series circuit, I = VR = 12V13.4Ω = 0.67 A
∵ There is no division of current in series. Therefore current through 12 Ω resistor = 0.67 A.

Question 10
How many 176 Ω resistors (in parallel) are required to carry 5 A on a 220 V line? [CBSE (Delhi) 2013]
Solution:
Suppose n resistors of 176 Ω are connected in parallel.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q10
Thus 4 resistors are needed to be connect.

Question 11
Show how you would connect three resistors, each of resistance 6 Ω, so that the combination has a resistance of (i) 9 Ω, (ii) 4Ω
Solution:
Here, R1 = R2 = R3 = 6 Ω.

(i) When we connect R1 in series with the parallel combination of R2 and R3 as shown in Fig. (a).
The equivalent resistance is
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q11
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q11.1

(ii) When we connect a series combination of R1 and R2 in parallel with R3, as shown in Fig. (b), the equivalent resistance is
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q11.2
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q11.3

Question 12
Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A ?
Solution:
Here, current, I = 5 A, voltage, V = 220 V
∴ Maxium power, P = I x V = 5 x 220 = 1100W
Required no. of lamps =Max.PowerPowerof1lamp=110010=110
∴ 110 lamps can be connected in parallel.

Question 13
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases ?
Solution:
(i) When the two coils A and B are used separately. R = 24 Ω, V = 220 V
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q13

(ii) When the two coils are connected in series,
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q13.1

(iii) When the two coils are connected in parallel.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q13.2

Question 14
Compare the power used in the 2 Ω resistor in each of the following circuits
(i) a 6 V battery in series with 1 Ω and 2 Ω resistors, and
(ii) a 4 V battery in parallel with 12 Ω and 2 Ω resistors.
Solution:
(i) The circuit diagram is shown in figure.
Total resistance, R = 1Ω + 2Ω = 3Ω
Potential difference, V = 6 V
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q14
Power used in 2Ω resistor = I2R = (2)2 x 2 = 8 W

(ii) The circuit diagram for this case is shown :
Power used in 2 resistor = v2R =422 = 8 W.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q14.1
[ ∵ Current is different for different resistors in parallel combination.]

Question 15
Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V ? [CBSE 2018]
Solution:
Power of first lamp (P1) = 100 W
Potential difference (V) = 220 V
NCERT Solutions for Class 10 Science Chapter 12 Electricity Chapter End Questions Q15

Question 16
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes ?
Solution:
Energy used by 250 W TV set in 1 hour = 250 W x 1 h = 250 Wh
Energy used by 1200 W toaster in 10 minutes = 1200 W x 10 min
= 1200 x 1060 = 200 Wh 60
Thus, the TV set uses more energy than the toaster.

Question 17
An electric heater of resistance 8 Ω draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.
Solution:
Here, R = 8 Ω, 1 = 15 A, t = 2 h
The rate at which heat is developed in the heater is equal to the power.
Therefore, P = I2 R = (15)2 x 8 = 1800 Js-1

Question 18
Explain the following:
(i) Why is tungsten used almost exclusively for filament of electric lamps ?
(ii) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal ?
(in) Why is the series arrangement not used for domestic circuits ?
(iv) How does the resistance of a wire vary with its area of cross-section ?
(v) Why are copper and aluminium wires usually employed for electricity transmission?
Answer:
(i) The tungsten is used almost exclusively for filament of electric lamps because it has a very high melting point (3300°C). On passing electricity through tungsten filament, its temperature reaches to 2700°C and it gives heat and light energy without being melted.
(ii) The conductors of electric heating devices such as bread-toasters and electric irons, are made of an alloy rather than a pure metal because the resistivity of an alloy is much higher than that of pure metal and an alloy does not undergo oxidation (or burn) easily even at high temperature.
(iii) The series arrangement is not used for domestic circuits because in series circuit, if one electrical appliance stops working due to some defect, than all other appliances also stop working because the whole circuit is broken.
(iv) The resistance of a wire is inversely proportional to its area of cross-section, i.e., Resistance R ∝ (1/πr2). If the area of cross section of a conductor of fixed length is increased, then resistance decreases because there are more free electrons for movement in conductor.
(v) Copper and aluminium wires usually employed for electricity transmission because they have very low resistances. So, they do not become too hot on passing electric current.

NCERT Solutions for Class 10 Science Chapter 12 Electricity

Electric current, potential difference and electric current, Ohms law, Resistance, Resistivity factors on which the resistance of a conductor depends; Series combination of resistors, parallel combination of resistors; and its application on daily life; Heating effect of Electric current, electric Power, Interrelation between P, V, and R.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 12
Chapter NameElectricity
Number of Questions Solved41
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Page 200
What does an electric circuit mean?
Electric circuit is a continuous and closed path made of conducting wires, through which the electric current flows. It comprises a cell, ammeter, voltmeter, plug key, etc.
Define the unit of current.
SI unit of electric current is ampere (A).
Ampere is the flow of electric charges through an area at the rate of one coulomb per second, i.e. if 1 coulomb of electric charge flows through a cross-section of wire for 1 second, then it would be equal to 1 ampere.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 200 Q1

Page 202

Question 1:
Name a device that helps to maintain a potential difference across a conductor.
Answer:
Cell or battery eliminator.

Question 2:
What is meant by saying that the potential difference between two points is 1 V?
Answer:
As we know that V = W / q
Thus, the potential difference between two points is one volt when one joule of work is done to carry a charge of one coulomb between the two points in the electric field.

More Resources for CBSE Class 10

Question 3:
How much energy is given to one coulomb of charge passing through a 6 V battery
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 202 Q3

Page 209

Question 1:
On what factors does the resistance of a conductor depend
Answer:
Resistance of a conductor depends upon:
(i) Resistivity of the material.
(ii) Length of the conductor.
(iii) Cross-sectional area of the conductor.

Question 2:
Will current flow more easily through a thick wire or thin wire of the same material when connected to the same source? Why
Answer:
The current flows more easily through a thick wire than through a thin wire because the resistance of thick wire is less than that of a thin wire as R ∝ 1/A.

Download NCERT Solutions for Class 10 Science Chapter 12 Electricity PDF

Question 3:
Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 209 Q3
Hence, the current through an electrical component also becomes half of its previous value.

Question 4:
Why are the coils of electric toasters and electric irons made of an alloy rather than a pure metal
Answer:
The coils of electric toaster and electric iron are made of an alloy rather than a pure metal because of the following reasons;
(i) The resistivity of an alloy is higher than that of a pure metal.
(ii) It has high melting point and does not oxidise.

Question 5:
Use the data in Table 12.2 of NCERT book to answer the following:
(a) Which among iron and mercury is a better conductor?
(b) Which material is the best conductor? ‘
Answer:
(a) Iron because its resistivity is less than mercury.
(b) Silver is the best conductor as it has least resistivity.

Page 213

Question 1:
Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5 Ω resistor, a 8 Ω resistor and a 12 Ω resistor and a plug key, all connected in series.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 213 Q1

Question 2:
Redraw the circuit of the above question, putting in an ammeter to measure the current through the resistors and a voltmeter to measure the voltage across the 12 resistor. What would be the reading in the ammeter and the voltmeter?
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 213 Q2
Total resistance of the circuit = R
Since all the three resistors are connected in series, so, the equivalent resistance R is equal to the sum of all resistance.
R = 5 Ω + 8 Ω + 12 Ω = 25 Ω
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 213 Q2.1
Page 216

Question 1:
Judge the equivalent resistance when the following are connected in parallel.
(a) 1 Ω and 106 Ω
(b) 1 Ω , 103 Ω and 106 Ω Answer:
Equivalent resistance in parallel combination of resistors is always less than the least resistance of any resistor in the circuit.
Hence, in both the given cases, the equivalent resistance is less than 1 Ω.

Question 2:
An electric lamp of 100 Ω, a toaster of resistance 50 Ω and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances and what is the current flows through it?
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 216 Q2

Question 3:
What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series ?
Answer:
Advantages of connecting electrical devices in parallel:

  1. When the appliances are connected in parallel with the battery, each appliance gets the same potential difference as that-of battery which is not possible in series connection.
  2. Each appliance has different resistances and requires different currents to operate properly. This is possible only in parallel connection, as in series connection, same current flows through all devices, irrespective of their resistances.
  3. If one appliance fails to work, other will continue to work properly.

Question 4:
How can three resistors of resistances 2 Ω, 3 Ω and 6 Ω be connected to give a total resistance of (a) 4 Ω (b) 1 Ω?
Answer:
(a) In order to get 4 Ω, resistance 2 Ω should be connected in series with the parallel combination of 3 Ω and 6 Ω.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 216 Q4

Question 5:
What is (a) the highest (b) the lowest total resistance that can be secured by combination of four coils of resistances 4 Ω, 8 Ω, 12 Ω, 24 Ω?
Answer:
(a) The highest resistance is secured by combining all four coils of resistance in series.
Rs = 4 Ω+ 8 Ω + 12 Ω + 24 Ω = 48 Ω
(b) The lowest resistance is secured by combining all four coils of resistance in parallel.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 216 Q5

Page 218

Question 1:
Why does the cord of an electric heater not glow while the heating element does?
Answer:
The cord of an electric heater is made up of metallic wire such as copper or aluminum which has low resistance while the heating element is made up of an alloy which has more resistance than its constituent metals. Also heat produced ‘H’ is
H = I2Rt
Thus, for the same current H oc R, so for more resistance, more heat is produced by heating element and it glows.

Question 2:
Compute the heat generated while transferring 96000 C of charge in one hour through a potential difference of 50 V.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Page 218 Q2

Question 3:
An electric iron of resistance 20 Q takes a current of 5 A. Calculate the heat developed in 30 s.
Answer:
Given R = 20 Ω, I = 5 A, t = 30 s
H = I2Rt = (5)2 x 20 x 30 = 15000 J = 1.5 x 104 J

Page 220

Question 1:
What determines the rate at which energy is delivered by a current?
Answer:
Electric power determines the rate at which energy is delivered by a current.

Question 2:
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
Answer:
Given I = 5 A, V = 220 V, t = 2 h Power,
p = VI = 220 x 5 = 1100 W
Energy consumed = Vlt = Pt
= 1100 x 2 = 2200 Wh

Textbook Questions

Question 1:
A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R’, then the ratio R/R’ is
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q1
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q1.1

Question 2:
Which of the following terms does not represent electrical power in a circuit?
(a) I2R
(b) IR2
(c) VI
(d) V2/R
Answer:
(b) P = V2/R = I2R = VI Option (b) does not represent electrical power.

Question 3:
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be
(a) 100 W
(b) 75 W
(c) 50 W
(d) 25 W
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q3

Question 4:
Two conducting wires of same material and of equal lengths and diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be
(a) 1:2
(b) 2:1
(c) 1:4
(d) 4:1
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q4

Question 5:
How is a voltmeter connected in the circuit to measure the potential difference between two points?
Answer:
A voltmeter is connected in parallel across any two points in a circuit to measure the potential difference between them with its +ve terminal to the point at higher potential and -ve terminal to the point at lower potential of the source.

Question 6:
A copper wire has a diameter 0.5 mm and resistivity of 1.6 X 10-8 Ωm. What will be the length of this wire to make its resistance 10 Ω? How much does the resistance change if the diameter is doubled?
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q6
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q6.1

Question 7:
The values of the current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q7
Plot a graph between V and I and calculate the resistance of that resistor.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q7.1

Question 8:
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q8

Question 9:
A battery of 9 V is connected in series with resistors of 0.2 Ω, 0.3 Ω, 0.4 Ω, 0.5 Ω and 12 Ω, respectively. How much current would flow through the 12 Ω resistor?
Answer:
Since all the resistors are in series, the same current, 0.67 A flows through the 12 Ω resistor.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q9

Question 10:
How many 176 Ω resistors (in parallel) are required to carry 5 A on a 220 V line?
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q10

Question 11:
Show how you would connect three resistors, each of resistance 6 Ω , so that the combination has a resistance of (i) 9 Ω , (it) 4 Ω .
Answer:
(i) When two 6 Ω resistances are in parallel and the third is in combination to this, the equivalent resistance will be 9 Ω.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q11
(ii) When two 6 Ω resistances are in series and the third is in parallel to them, then it will be 4 Ω.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q11.1

Question 12:
Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A?
Answer:
Since, N bulbs of power P each connected in parallel will make the total power of NP,
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q12

Question 13:
A hot plate of an electric oven connected to 220 V line has two resistance coils A and B, each of 24 Q resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q13

Question 14:
Compare the power used in the 2 Ω resistor in each of the following circuits.
(i) a 6 V battery in series with 1 Ω and 2 Ω resistors, and
(ii) a 4 V battery in parallel with 12 Ω and 2 Ω resistors.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q14

Question 15:
Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q15

Question 16:
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
Answer:
Energy consumed by 250 W TV set in 1 h = 250 x 1 = 250 Wh.
Energy consumed by 1200 W toaster in 10 min = 1200 X 1/6 = 200 Wh.
∴ Energy consumed by TV set is more than the energy consumed by toaster in the given timings.

Question 17:
An electric heater of resistance 8 f2 draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions Q17

Question 18:
Explain the following.
(a) Why is the tungsten used almost exclusively for filament of electric lamps?
(b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
(c) Why is the series arrangement not used for domestic circuits?
(d) How does the resistance of a wire vary with its area of cross-section?
(e) Why are copper and aluminum wires usually employed for electricity transmission?
Answer:
(a) It has high melting point and emits light at a high temperature.
(b) It has more resistivity and less temperature coefficient of resistance.
(c) (i) All appliances do not get same potential in series arrangement.
(ii) All appliances cannot be individually operated.
(d) R ∝ =1 / Area of cross – section.
(e) They are very good conductors of electricity.

Short Answer Type Questions

Question 1:
Three 2 Ω resistors, A, B and C are connected as shown in figure. Each of them dissipates energy and can withstand a maximum power of 18 W without melting. Find the maximum current that can flow through the three resistors.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions SAQ Q1

Question 2:
Should the resistance of an ammeter be low or high? Give reason.
Answer:
The resistance of an ammeter should be low so that it will not disturb the magnitude of current flowing through the circuit when connected in series in a circuit.

Question 3:
How does use of a fuse wire protect electrical appliances?
Answer:
The fuse wire is always connected in series with the live wire or electrical devices. If the flow of current exceeds the specified preset value due to some reason, the heat produced melts it and disconnects the circuit or the device from the mains. In this way, fuse wire protects the electrical appliances.

Question 4:
What is electrical resistivity? In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 5 A. The reading of the ammeter decreases to half when the length of the wire is doubled. Why?
Answer:
The resistance offered by a metallic wire of unit length and unit cross-sectional area is called electrical resistivity.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions SAQ Q4
Hence, when the length of wire is doubled, the resistance becomes double and current decreases to half.

Question 5:
A current of 1 ampere flows in a series circuit containing an electric lamp and a conductor of 5 Ω when connected to a 10 V battery. Calculate the resistance of the electric lamp.
Now if a resistance of 10 Ω is connected in parallel with this series combination, what change (if any) in current flowing through 5 Ω conductor and potential difference across the lamp will take place? Give reason.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions SAQ Q5
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions SAQ Q5.1

Question 6:
Why is parallel arrangement used in domestic wiring?
Answer:
Parallel arrangement is used in domestic wiring because
(i) Each appliance gets the same voltage as that of the mains supply.
(ii) If one component is switched off, others can work properly.
(iii) Fault in any branch of the circuit can be easily identified.

Question 7:
B1, B2 and B3 are three identical bulbs connected as shown in figure. When all the three bulbs glow, a current of 3A is recorded by the ammeter A.

NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions SAQ Q7
(i) What happens to the glow of the other two bulbs when the bulb B j gets fused?
(ii) What happens to the reading of A1 ,A2 , A3 and A when the bulb B2 gets fused?
(iii) How much power is dissipated in the circuit when all the three bulbs glow together?
Answer:
(i) Since B1 ,B2 and B3 are in parallel, the potential difference across each of them will remain same. So when the bulb B1 gets fused, B2 and B3 have the same potential and continues with the same energy dissipated per second, i.e. they will glow continuously as they were glowing before.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions SAQ Q7.1
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions SAQ Q7.2

Long Answer Type Questions

Question 1:
Three incandescent bulbs of 100 W each are connected in series in an electric circuit. In another circuit, another set of three bulbs of the same wattage are connected in parallel to the same source.
(а) Will the bulb in the two circuits glow with the same brightness? Justify your answer.
(b) Now let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions LAQ Q1
(a) The bulbs in the two circuits will not glow equally bright as the current through them is not the same.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions LAQ Q1.1
(b) As one bulb fuses, the other bulbs in the series circuit will not glow because the circuit becomes an open circuit. While the rest of bulbs in parallel circuit will continue to glow without getting disturbed because in parallel combination, current gets additional paths to flow.

Question 2:
Find out the following in the electric circuit given in figure:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions LAQ Q2
Answer:
NCERT Solutions for Class 10 Science Chapter 12 Electricity Text Book Questions LAQ Q2.1
(e) No difference, since the ammeters are connected in series and same current will pass through them, so reading of both ammeters will be same.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
To determine the equivalent resistance of two resistors when connected in series, a student arranged the circuit components as shown in the diagram. But he did not succeed to achieve the objective. [CCE 2010]
NCERT Solutions for Class 10 Science Chapter 12 Electricity MCQs Q1
Which of the following mistakes has been committed by him in setting up the circuit?
(a) Position of ammeter is incorrect
(b) Position of voltmeter is incorrect
(c) Terminals of ammeter are wrongly connected
(d) Terminals of voltmeter are wrongly connected
Answer:
(c) Because positive terminal of ammeter must be connected with positive terminal of cell and negative terminal of an ammeter must be connected to negative terminal of a cell.

Question 2.
For the given circuit, name the components which are connected in parallel. [CCE 2011]
NCERT Solutions for Class 10 Science Chapter 12 Electricity MCQs Q2
(a) R1 and R2
(b) R1, R2 and V
(c) R2 and V
(d) R1 and V
Answer:
(b) The components R1, R2 and V are connected in parallel combination. Because terminals of the resistance and voltmeter are connected together.

Question 3.
A student arranges the following circuit to get equivalent resistance of a series combination of two resistors R1 and R2.
NCERT Solutions for Class 10 Science Chapter 12 Electricity MCQs Q3
Which one of the following statements will be true for this circuit [CCE 2007]
(a) It gives incorrect reading for current I as well as potential difference V
(b) It gives correct reading for current I but incorrect reading for potential difference V
(c) It gives correct reading for potential difference V but incorrect reading for current I
(d) It gives correct reading for both I and V
Answer:
(b) The voltmeter should be connected across the components of and R2 to give correct reading for potential difference.

Question 4.
An ammeter has 20 divisions between 0 mark and 2A mark on its scale. The least count of ammeter is
(a) 0.01A
(b) 0.2A
(c) 0.1A
(d) 1A
Answer:
(c) Number of divisions = 20
Maximum reading of ammeter = 2 A
Least count of ammeter = 2/20 = 1/10 = 0.1 A

Question 5.
A student finds that there are 20 divisions between zero mark and 1V mark of a voltmeter. The least count of voltmeter is
(a) 0.1 V
(b) 0.01 V
(c) 0.05 V
(d) 1.0 V
Answer:
(c) Number of divisions = 20
Maximum reading of the voltmeter = 1 V
Least count of voltmeter = 1/20 = 0.05 V

Question 6.
The current flowing through a resistor connected in an electric circuit and the potential difference applied across its ends are shown in figure alongside.
NCERT Solutions for Class 10 Science Chapter 12 Electricity MCQs Q6
The value of the resistance of the resistor is [CCE2013]
(a) 1 Ω
(b) 5 Ω
(c) 8 Ω
(d) 10 Ω
Answer:
(d) Reading from ammeter (7) = 180 mA= 0.18 A,
reading from voltmeter (V) = 1.8 V
Resistance of the resistor R = V/I = 1.8/0.18 = 180/18 = 10Ω

Question 7.
Which of the following is the correct method to connect the ammeter and voltmeter with resistance in the circuit to verify Ohm’s law? [CCE 2012]
(a) Ammeter and voltmeter in series
(b) Ammeter in series and voltmeter in parallel
(c) Ammeter in parallel and voltmeter in series
(d) Ammeter and voltmeter in parallel
Answer:
(b) In a circuit, ammeter should be connected in series, while voltmeter in parallel.

Question 8.
In an experiment on studying the dependence of the current I flowing through a given resistor on the potential difference V applied across it, a student has to change the value of the current. For doing this, he should change the
(a) number of cells used
(b) resistor itself
(c) ammeter used in the circuit
(d) Voltmeter used in the circuit
Answer:
(a) If we change the number of cells in electric circuit, the potential difference will change and as a result current flowing in the circuit changes.

Question 9.
A milliammeter had graduations marked 0, 100, 200, 300, 400 and 500. The space between 0 mark and 100 mark is divided into 20 divisions. If the pointer of the milliammeter is indicating the seventh graduation after 300 mark, the current flowing in the circuit is
(a) 335 mA
(b) 330 mA
(c) 331mA
(d) 340 mA
Answer:
(a) Number of divisions = 20
Least count of milliammeter = (100-0) / 20 = 5 mA
Milliammeter reading = 300 + 7 x 5 = 335 mA

Question 10.
If a student while studying the dependence of current on the potential difference keeps the circuit closed for a long time to measure the current and potential difference, then
(a) ammeter’s zero error will change
(b) ammeter will give more reading
(c) voltmeter will show constantly higher readings
(d) resistor will get heated up and its value will change
Answer:
(d) If the circuit is closed for a long time, then current flows in it for a long time which results that the resistor is heated.

Question 11.
To determine the eguivalent resistance of two resistors connected in series, a student prepared two electric circuits, correct reading of ammeter in the circuits is [CCE 2015]
NCERT Solutions for Class 10 Science Chapter 12 Electricity MCQs Q11
(a) In circuit I, 1.0 A and in II, 0.1 A
(b) In both circuits I and II, 1.0 A
(c) In circuit I, 0.1 A and in II, 1.0 A
(d) In both circuits I and II, 0.1 A
Answer:
(b) Equivalent resistance of two resistors 3.5Ω and 1Ω in both the circuits I and II is R = 3.5 + 1 = 4.5 Ω
As, I = V/R = 4.5/4.5 = 1A
Therefore, current in both the circuits I and II is 1.0 A.

Question 12.
When parallel resistors are of three different values, the potential difference across its terminals is [CCE 2015]
(a) greatest across smallest resistance
(b) greatest across largest resistance
(c) equal across each resistance
(d) least across the smallest resistance
Answer:
(c) Potential difference across each resistor is same in parallel combination of resistors.

NCERT Solutions for Class 10 Science Chapter 12 Electricity (Hindi Medium)

NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 1
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 2
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 3
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 4
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 5
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 6
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 7
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 8
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 9
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 10
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 11
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 12
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 13
NCERT Solutions for Class 10 Science Chapter 12 Electricity Hindi Medium 14

Class 10 Science Electricity Mind Map

Electricity
Study of Electric Charges at Rest and in Motion

Charge
Something associated with the matter due to which it produces and experiences electric and magnetic effects. Resides on the outer surface of the conductor.
Q = ne S.I. unit coulomb (C)

Electric Current (I)
The time rate of flow of charge (Q) through any cross-section
I = Qt S.I. unit ampere (A)

Types of Current
Direct Current
Current whose magnitude and direction does not vary with time.

Alternating Current
Current whose magnitude and direction periodically changes with time.

Electric Potential
Work done per unit charge
V = WQ
S.I. unit volt

Ohm’s law: If the physical conditions remain same, current I ∝ V => V = IR
R-electric resistance Substances which obey ohm’s law called ohmic and that do not obey called non-ohmic substances.

Dependence of Resistance

On length (l) and area of cross-section (A)
R ∝ l
∝ 1A
R = ρlA
ρ = resistivity
Resistivity depends on the material of the conductor only.

On Temperature
Rt = R0( 1 + αt)
α = temperature coefficient of resistance

Resistance (R): Obstruction offered to flow of electrons.
SI unit ohm
Resistance, R ∝ ℓ2m
l = length and
m = mass of conducting wire

After stretching, if length increases by n times then resistance will increase by n2 times i.e., R2 = n2 R1. Similarly
if radius be reduced to 1n times then area of cross-section decreases 1n2 times so the resistance becomes n4 times i.e.. R2 = n4 R1
After stretching, if length of a conductor increases by x%, then resistance will increase by 2x% (valid only if x< 10%).

  • Using n conductors of equal resistance, the number of possible combinations is 2n-1 .
  • If the resistances of n conductors are totally different, then the number of possible combinations will be 2n .
  • If n identical resistances are first connected in series and then in parallel, the ratio of the equivalent resistance is given by
    RsRp=n21
  • If a wire of resistance R is cut in n equal parts and then these parts are collected to form a bundle, then equivalent resistance of combination will be Rn2
  • If equivalent resistance of R1 and R2 in series and parallel be Rs and Rp respectively, then
    R1 = 12[Rs+R2s−4RsRp−−−−−−−−−−√]
    and R2 = =12[Rs−R2s−4RsRp−−−−−−−−−−√]

Grouping of Resistances

Series Grouping of Resistances
Equivalent resistance, resistance, Rs = R1 + R2 + … + Rn
In this case same current flows through each resistance but potential difference in the ratio of resistance

Parallel Grouping of Resistances
1RP=1R1+1R2+…+1Rn
In this case same potential across each resistance but current distributes in the reverse ratio of their resistances

Electric Circuit
The arrangement of various electrical components along which electric current flow
NCERT Solutions for Class 10 Science Chapter 12 Electricity Mind Map 1

Heating Effect of Electric Current
As current flows through a conductor, the free electrons lose energy which is converted into heat.
Joule’s heating law
H ∝ I2
H ∝ R
H ∝ t
H = I2Rt = VIt

Practical Applications

  • Electric heater, electric iron and water heater, etc. work on the principle of heating effect of current
  • Electric bulb glows when electric current flows through the filament of the bulb

Electric Power
Rate at which electric energy is dissipated or consumed in a circuit,
P = VI ,
or P = I2R = V2R

Watt is a smaller unit of power, its other bigger units are kilowatt (KW),
Megawatt (MW) and Horsepower (HP)
1 KW = 103W 1 MW = 106W
1 hp =746 W
The commercial unit of electrical energy is 1 Kwh.
1 Kwh = 3.6 × 106J

Elements of Circuit
Cell
Direct current source of electromotive force. Combination of two or more cells is called battery.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Mind Map 2

Rheostat
Wire of special type of alloy like manganin, Eureka, nichrome, etc. is wound on a hollow cylinder of china clay. It controls the current in the electric circuit.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Mind Map 3

Switch
It is used to close or open the electric circuit, controls the movement of electrons in a circuit.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Mind Map 4

Voltmeter
Measures the potential difference between two points in the circuit. Its resistance is high and it is used in parallel with the resistance wire.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Mind Map 5

Fuse
It is a safety device having very thin wire which is made up of either tin or alloy of tin and lead.
This wire has low melting point so it melts and breaks the circuit easily if the current in the circuit exceeds.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Mind Map 6

Ammeter
Measures the value of current flowing in the circuit.
The resistance of ammeter is small and it is used in series with the circuit.
NCERT Solutions for Class 10 Science Chapter 12 Electricity Mind Map 7

LED
It is a device which glows even if a weak electric current is allowed to flow through it

Now that you are provided all the necessary information regarding Electricity class 10 NCERT solutions and we hope this detailed article on NCERT Solutions For Class 10 Science Chapter 12 Electricity is helpful. If you have any doubt regarding this article or  NCERT Solutions For Class 10 Science Chapter 12 Electricity, leave your comments in the comment section below and we will get back to you as soon as possible.

NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World

NCERT Solutions For Class 10 Science Chapter 11 Human Eye And Colourful World: In this article, you will find out all the necessary information regarding class 10 science chapter 11 NCERT solutions. Practicing NCERT class 10 science chapter 11 notes will help candidates to bag a good score in class 10 board exam. Further having good knowledge of the unit human eye and colorful world class 10 science NCERT Solutions will build a strong foundation in clearing the Engineering competitive exams as this unit comes under the subject Physics.

The questions in each and every exercise of Human Eye and Colourful world comes with the answer and a detailed, step-by-step solution for better understanding by the student. So Read on to find out everything about NCERT Solutions For Class 10 Science Chapter 11 Human Eye And Colourful World to make a good grade in CBSE Class 10 Board exam.

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 11 Human Eye And Colourful World, let’s have an overview of list of topics and subtopics under class 10 science chapter 11 NCERT solutions:

  1. The Human Eye And The Colourful World
  2. The Human Eye
  3. Defects Of Vision And Their Correction
  4. Refraction Of Light Through A Prism
  5. Dispersion Of White Light By A Glass Prism
  6. Atmospheric Refraction
  7. Scattering Of Light

Free download NCERT Solutions for Class 10 Science Chapter 11 Human Eye And Colourful World PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 11 Intext Questions

Page Number: 190

Question 1
What is meant by power of accommodation of the eye ?
Answer:
The power of accommodation of the eye is the maximum variation of its power for focusing on near and far (distant) objects.

Question 2
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision ?
Answer:
Concave lens.

Question 3
What is the far point and near point of the human eye with normal vision ?
Answer:
For a human eye with normal vision the far point is at infinity and near point is 25 cm from the eye.

Question 4
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from ? How can it be corrected?
Answer:
The child is suffering from myopia. The child should use concave lens of suitable focal length.

NCERT Solutions for Class 10 Science Chapter 11 Textbook Chapter End Questions

Question 1
The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
(a) presbyopia
(b) accommodation
(c) near – sightedness
(d) far – sightedness
Answer:
(b) Accommodation

Question 2
The human eye forms the image of an object at its
(a) cornea
(b) iris
(c) pupil
(d) retina
Answer:
(d) Retina

Question 3
The least distance of distinct vision for a young adult with normal vision is about
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
Answer:
(c) 25 cm

Question 4
The change in focal length of an eye lens is caused by the action of the
(a) pupil
(b) retina
(c) ciliary muscles
(d) iris
Answer:
(c) Ciliary muscles

Question 5
A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision ?
Solution:
(i) ∵ Power of distant viewing part of the lens, P1 = -5.5 D
∴ Focal length of this part, f1 = 1p1 = 1−5.5 m = -0.182 m = -18.2 cm

(ii) For near vision,
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Chapter End Questions Q5

Question 6
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem ?
Solution:
The remedial lens should make the objects at infinity appear at the far point.
Therefore, for object at infinity, u = ∞
Far point distance of the defected eye, ν = – 80 cm
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Chapter End Questions Q6
Negative sign shows that the remedial lens is a concave lens.

Question 7
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct the defect ? Assume that the near point of the normal eye is 25 cm.
Solution:
(i) The near point N of hypermetropic eye is farther away from the normal near point N.
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Chapter End Questions Q7

(ii) In a hypermetropic eye, the image of nearby object lying at normal near point N (at 25 cm) is formed behind the retina.
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Chapter End Questions Q7.1

(iii) Correction of hypermetropia : The convex lens forms a virtual image of the object (lying at normal near point N) at the near point N’ of this eye.
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Chapter End Questions Q7.2
The object placed at 25 cm from the correcting lens must produce a virtual image at 1 m or 100 cm.
Therefore, u = – 25 cm, ν = 100 cm
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Chapter End Questions Q7.3
The positive sign shows that it is a convex lens.

Question 8
Why is a normal eye not able to see clearly the objects placed closer than 25 cm ?
Answer:
At distance less than 25 cm, the ciliary muscles cannot bulge the eye lens any more, the object cannot be focused on the retina and it appears blurred to the eye, as shown in the given figure.
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Chapter End Questions Q8

Question 9
What happens to the image distance in the eye when we increase the distance of an object from the eye ?
Answer:
The eye lens of a normal eye forms the images of objects at various distances on the same retina. Therefore, the image distance in the eye remains the same.

Question 10
Why do stars twinkle ?
Answer:
Stars appear to twinkle due to atmospheric refraction. The light of star after the entry of light in earth’s atmosphere undergoes refraction continuously till it reaches the surface of the earth. Stars are far away. So, they are the point source of light. As the path of light coming from stars keep changing, thus the apparent position of stars keep changing and amount of light from stars entering the eye keeps twinkling. Due to which a star sometimes appear bright and sometimes dim, which is the effect of twinkling.

Question 11
Explain why the planets do not twinkle ?
Answer:
The planets are much nearer to the earth than stars and because of this they can be considered as large source of light. If a planet is considered to be a collection of a very large number of point sources of light, then the average value of change in the amount of light entering the eye from all point size light sources is zero. Due to this the effect of twinkling is nullified.

Question 12
Why does the sun appear reddish early in the morning ?
Answer:
The light coming from the sun passes through various denser layers of air in the earth’s atmosphere before reaching our eyes near the horizon. Most of the part of blue light and light of small wavelength gets scattered by dust particles near the horizon. So, the light reaching our eyes is of large wavelength. Due to this the sun appears reddish at the time of sunrise and sunset.

Question 13
Why does the sky appear dark instead of blue to an astronaut ?
Answer:
As an astronaut moves away from the atmosphere of earth, the atmosphere becomes thin. Due to the absence of molecules (or dust particles) in air, the scattering of light does not take place. Thus, sky appears dark in the absence of scattering.

NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World

Functioning of a lens in human eye, defects of vision and their corrections, applications of spherical mirrors and lenses. Refraction of light through a prism, dispersion of light, scattering of light, applications in daily life.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 11
Chapter NameHuman Eye and Colourful World
Number of Questions Solved17
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Page 190

Question 1.
What is meant by power of accommodation of the eye?
Answer:
The power Of accommodation of the eye is the ability of the eye to observe the distinct objects clearly which are situated at a large distance from the eye. The ciliary muscles are responsible to change the focal length Of the eye lens. The value of the power of accommodation Of the normal human eye is (d = 25 cm) = 100/f = 100/d = 100/25 = 4 dioptres. The value of power of accommodation Of human eye is about 4D

Question 2.
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
Answer:
The far point for myopic eye is 1.2m.
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Page 190 Q2

More Resources for CBSE Class 10

Question 3.
What is the far point and near point of the human eye with normal vision ?
Answer:
For human eye with normal vision, far point is at infinity and near point is at 25 cm from the eye.
Download NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World PDF

Question 4.
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from ? How can it be corrected ?
Answer:
As the child has difficulty in reading the blackboard, he is suffering from myopia or short sightedness. To correct this defect, he has to use spectacles with concave lens of suitable focal length.

Page 197 – 198
Question 1.
The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
(a) presbyopia
(b) accommodation
(c) near-sightedness
(d) far-sightedness
Answer:
(b) Human eye can change the focal length of the eye lens to see the objects situated at various distances from the eye. This is possible due to the power of accommodation of the eye lens.

Question 2.
The human eye forms the image of an object at its
(a) cornea (b) iris (c) pupil (d) retina
Answer:
(d) The human eye forms the image of an object at its retina.

Question 3.
The least distance of distinct vision for a young adult with normal vision is about
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
Answer:
(c) The least distance of distinct vision is the minimum distance of an object to see clear and distinct image. It is 25 cm for a young adult with normal visions.

Question 4.
The change in focal length of an eye lens is caused by the action of the
(a) pupil
(b) retina
(c) ciliary muscles
(d) iris
Answer:
(c) The relaxation or contraction of ciliary muscles changes the curvature of the eye lens. The change in curvature of the eye lens changes the focal length of the eyes. Hence, the change in focal length of an eye lens is caused by the action of ciliary muscles.

Question 5.
A person needs a lens of power – 5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?
Answer:
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Page 197 Q5

Question 6.
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Answer:
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Page 197 Q6

Question 7.
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye ¡s 1 m. What ¡s the power of a lens required to correct this defect? Assume that near point of the normal eye is 25 cm.
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Page 197 Q7
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Page 197 Q7.1

Question 10.
Why do stars twinkle?
Answer: The stars twinkle at night, because the star light reaching Our eyes increases and decreases continuously due to atmospheric refraction. When star light reaching our eyes increases, the star looks bright and when the star light reaching our eyes decreases, it appears dim.

Question 11.
Explain why the planets do not twinkle ?
Answer:
Planets being close to earth appear larger in size. A planet can be Considered as a collection of large number of small sized objects. Twinkling effect Of these objects cancel each other. so, planets do not appear to twinkle.

Question 12.
Why does the sun appear reddish early in the morning?
Answer: At sunrise, the sun looks almost reddish because only red colour which is least scattered is received by our eye and appears to come from sun. Hence the appearance Of sun at sunrise, near the horizon looks almost reddish.

Question 13.
Why does the sky appear dark of blue to an astronaut?
Answer:
At such huge heights due to absence of atmosphere, no scattering of the light takes place. Therefore sky appears dark.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
The human eye forms the image of an object at its [NCERT]
(a) cornea
(b) iris
(c) pupil
(d) retina
Answer:
(d) Retina is the light sensitive surface of eye on which the image is formed.

Question 2.
The human eye can focus objects at different distances by adjusting the focal length of eye lens. This is due to [NCERT]
(a) presbyopia
(b) accommodation
(c) nearsightedness
(d) farsightednes
Answer:
(b) Accommodation is the ability of eye lens to focus both near and distant objects by adjusting its focal length.

Question 3.
The change in focal length of eye lens is caused by action of [NCERT]
(a) pupil
(b) retina
(c) ciliary muscles
(d) iris
Answer:
(c) Ciliary muscles contract and extend in order to change the lens shape for focussing image ayretina.

Question 4.
The least distance of distinct vision for a young adult with normal vision is about [NCERT]
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
Answer:
(c) The minimum distance at which an object can be seen most distinctly without any strain is 25 cm.

Question 5.
At noon the Sun appears white as [NCERT Exemplar]
(a) light is least scattered
(b) all the colours of the white light are scattered away
(c) blue colour is scattered the most
(d) red colour is scattered the most
Answer:
(a) At noon, the Sun appears white because the light from the Sun is directly over head and travel relatively shorter distance. The Sun appears white as only a little of the blue and violet colours are scattered.

Question 6.
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power [NCERT Exemplar]
(a) +0.5 D
(b) -0.5 D
(c) +0.2 D
(d) -0.2 D
If a person cannot see distinctly, objects kept beyond 21 m, then he is suffering from myopia.
Answer:
(b) As the person has the eye defect, myopia, therefore a concave lens has to be used whose focal length will be f = -2 m (using sign convention). Thus,
Power, P = 1/f [where, f is focal length in metre.]
= 1/-2 = -0.5D .

Question 7.
Which of the following phenomena of light are involved in the formation of a rainbow? [NCERT Exemplar]
(a) Reflection, refraction and dispersion
(b) Refraction, dispersion and total internal reflection
(c) Refraction, dispersion and internal reflection
(d) Dispersion, scattering and total internal reflection
Answer:
(c) A rainbow is caused by dispersion, refraction and internal reflection of sunlight by tiny water droplets, present in the atmosphere and always formed in a direction opposite to that of the Sun. The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally and finally refract it again when it comes out of the raindrop.

Question 8.
A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in figure. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky? [NCERT Exemplar]
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World MCQs Q8
(a) Only (i)
(b) Only (ii)
(c) Only (iii)
(d) Only (iv)
Answer:
(b) In (ii) case, after dispersion, the third colour from the top corresponds to colour of the sky, i.e. blue.
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World MCQs Q8.1

Question 9.
A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book. Which of the following statements is correct?
(a) The near point of his eyes has receded away
(b) The near point of his eyes has come closer to him
(c) The far point of his eyes has come closer to him
(d) The far point of his eyes has receded away
Hypermetropia may have blurred vision to a person when looking at an object close to them and clearer 1 vision while looking at an object at the distance.
Answer:
(a) The student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book because he is suffering from hypermetropia or far sightedness. He can see distant objects clearly but cannot see nearby objects distinctly.

Question 10.
In the following diagram, the path of a ray of light passing through a glass prism is shown below.
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World MCQs Q10
In this diagram, the angle of incidence, the angle of emergence and the angle of deviation respectively, are [CBSE2014]
(a) X, R and T
(b) Y, Q and T
(c) X, Q and P
(d) Y, Q and P
Answer:
(d) Angle of incidence is the angle made by the incident ray with the normal to the first surface of prism, which is shown by angle Y. Angle of emergence is the angle made by the emergent ray with the normal to the surface when it comes out from the prism after refraction, which is shown by angle Q. Angle of deviation is the angle between the incident ray and the emergent ray, which is shown by angle P.

NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World (Hindi Medium)

NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 1
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 2
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 3
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 4
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 5
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 6
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 7
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 8
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 9
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 10
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 11
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 12
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 13
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 14
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 15
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Hindi Medium 16

Class 10 Science Human Eye and Colourful World Mind Map

Human Eye
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Mind Map 1
The organ which gives us the sense of light or enables us to see. It interprets the shapes, colours and dimensions of the

Parts of the Human Eye
Retina: It is a light sensitive screen on which image is formed.
It contains rods sensitive to intensity of light and cones sensitive to colour.
Cornea: Thin membrane acts like a lens which allow light to enter the eye.
Sclera: Outer part of the eye, protects interior of the eye.
Eye Lens: Convex lens made of transparent, crystalline and flexible jelly like material.
Refractive index of eye lens is 1.437
Ciliary Muscles: Modify the shape of eye lens.
Pupil: Hole in the middle of iris through which light enters.
Iris: Controls the amount of light entering the eye by changing the size of pupil.
Optical Nerve: Nerves take the image to the brain in the form of electrical signals.

Defects of Human Eye
Myopia or Short Sightedness: can see nearby objects but cannot see far off objects distinctly. Corrected by using a concave lens.
Hypermetropia or Long Sightedness: can see far off objects clearly but cannot see nearby objects clearly. Corrected by convex lens
Presbyopia: It is due to lessening of the flexibility of the crystalline lens and weakening of ciliary muscles. Corrected by using bifocal lenses.
Astigmatism: Refractive problem responsible for blurry vision. Corrected by using cylindrical lenses.
Cataract: It is a clouding of the lens in the eye. Corrected using cataract surgery

Power of Accommodation
The ability of the eye lens to adjust its focal length so as to see the objects clearly located anywhere. Near point of the human eye is 25 cm and far point of the human eye is infinity.

ObjectCiliary musclesSuspensory ligamentsMuscle tension on lensLens shape
NearContractSlackenedLowThick
DistantRelaxStretchedHighThin

Persistence of Vision
Image of any object seen persists on the retina for 1/16 second even after the removal of the object. This property is used in cinematography.

Reason for Hypermetropia

  • Increase in focal length of eye lens
  • Shortening of eye-ball
    NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Mind Map 2

Reason for Myopia

  • Excessive curvature of cornea
  • Elongation of eye-ball
    NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World Mind Map 3

Refraction
Bending of light when it passes obliquely from one medium to another medium

Dispersion
Splitting of white light into its component colours – VIBGYOR.
Red colour deviates least and violet deviates most
NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World 4

Cause of Dispersion
Refractive index of material for different wavelengths is different.
µ ∝1λ µv > µr

Spectrum
Band of seven component colours VIBGYOR on a white screen

Rainbow
Seven colours band of sunlight in the form of bow in the sky. It is formed due to reflection, refraction and dispersion of sunlight by tiny water droplets. To observe rainbow, observer should stand with its back towards sun.

Colour
The sensation received by the eye (rod cells of the eye) due to light coming from an object.

Primary Rainbow

  • Two refraction and one total internal reflection
  • Subtends an angle of 42° at the eye of the observer
  • Innermost arc is violet and outermost is red
  • More bright

Secondary Rainbow

  • Two refraction and two total internal reflection
  • Subtends an angle of 52.5° at the eye
  • Innermost arc is red and outermost is violet
  • Less bright in comparison to primary rainbow

Atmospheric Refraction
Phenomena due to Refraction of light by atmosphere

  • Twinkling of stars
  • Stars seen higher than they actually are
  • Advance sunrise and delayed sunset
  • Flattering of the sun at morning and evening

Scatttering of Light

  • Rayleigh scattering Intensity of scattered light ∝ 1/λ4
  • Tyndall effect The smoke particles become visible
  • The reddening of the sun at sunrise and sunset
  • Blue colour of sky
  • The sky looks dark in absence of atmosphere
  • Danger signals are of red coloured

Now that you are provided all the necessary information regarding  NCERT Solutions For Class 10 Science Chapter 11 Human Eye And Colourful World and we hope this detailed article on class 10 science chapter 11 NCERT solutions is helpful. If you have any questions related to this article or NCERT Solutions For Class 10 Science Chapter 11 Human Eye And Colourful World, reach ys through the comment section below and we will get back to you as soon as possible.

NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction

NCERT Solutions For Class 10 Science Chapter 10 Light Reflection and Refraction: In this article, you candidates can find light reflection and refraction class 10 NCERT solutions. Working on the light chapter of class 10 NCERT solutions will help candidates to build a strong foundation over the subject Physics. Knowing light reflection and refraction class 10 questions and answers will help students of class 10 to bag a decent score in class 10 board exams as well.

Along with NCERT Solutions For Class 10 Science Chapter 10 Light Reflection and Refraction candidates can also find light reflection and refraction class 10 numericals questions in this article. Go through them will help candidates get a clear idea about how to approach the problems which in turn helps you to solve them in the most efficient way. So why wait? Read on to find out everything about light reflection and refraction class 10 important questions with answers here.

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 10 Light Reflection and Refraction, let’s have an overview of topics and subtopics under NCERT class 10 science book activities solutions chapter 10:

  1. Light – Reflection And Refraction
  2. Reflection Of Light
  3. Spherical Mirrors
  4. Refraction Of Light

Free download NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 10 Intext Questions

Page Number: 168

Question 1
Define the principal focus of a concave mirror.
Answer:
The principal focus of a concave mirror is a point on its principal axis to which all the light rays which are parallel and close to the axis, converge after reflection from the concave mirror.

Question 2
The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
Answer:
Focal length = 12 x Radius of curvature = 12 x 20 cm = 10 cm

Question 3
Name a mirror that can give an erect and enlarged image of an object.
Answer:
Concave mirror.

Question 4
Why do we prefer a convex mirror as a rear-view mirror in vehicles ?
Answer:
We prefer a convex mirror as a rear-view mirror in vehicles because of two reasons :

  1.  A convex mirror always produces an erect image of the objects.
  2.  The image formed in a convex mirror is highly diminished or much smaller than the object, due to which a convex mirror gives a wide field of view of the traffic behind. A convex mirror enables the driver to view such larger area of the traffic behind him.

Page Number: 171

Question 1
Find the focal length of a convex mirror whose radius of curvature is 32 cm.
Solution:
R = +32 cm and f=R2=+322=+16cm

Question 2
A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located ?
Solution:
Because the image is real, so magnification m must be negative.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Intext Questions Page 171 Q2
Thus the image is located at a distance of 30 cm from the mirror on the object side of the mirror.

Page Number: 176

Question 1
A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal ? Why ?
Answer:
The light-ray bends towards the normal because the ray of light goes from a rarer medium to a denser medium.

Question 2
Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass ? The speed of light in vacuum is 3 x 108 ms-1.
Solution:
Refractive index of glass, n8 = 1.50
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Intext Questions Page 176 Q2

Question 3
Find out, from Table 10.3, the medium having highest optical density. Also find the medium with lowest optical density.
Answer:
From table 10.3, diamond has highest refractive index (= 2.42), so it has highest optical density.
Air has lowest refractive index (= 1.0003),
so it has lowest optical density.

Question 4
You are given kerosene, turpentine and water. In which of these does the light travel fastest ? Use the information given in Table 10.3.
Answer:
For kerosene, n = 1.44
For turpentine, n = 1.47
For water, n = 1.33
Because water has the lowest refractive index, therefore light travels fastest in this optically rarer medium than kerosene and turpentine oil.

Question 5
The refractive index of diamond is 2.42. What is the meaning of this statement?
Answer:
By saying that the refractive index of diamond is 2.42, we mean that the speed of light in diamond is lower by a factor of 2.42 relative to that in vacuum.

Page Number: 184

Question 1
Define 1 dioptre of power of a lens.
Answer:
One dioptre is the power of a lens whose focal length is 1 metre.

Question 2
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object ? Also, find the power of the lens. , Sol. Here, u — +50 cm ..
Solution:
Here ν = +50cm
Because the real image is of the same size as the object,
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Intext Questions Page 184 Q2

Question 3
Find the power of a concave lens of focal length 2 m.
Solution:
Because the focal length of a concave lens is negative,
therefore f = -2 m
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Intext Questions Page 184 Q3

NCERT Solutions for Class 10 Science Chapter 10 Textbook Chapter End Questions

Question 1
Which one of the following materials cannot be used to make a lens ?
(a) Water
(b) Glass
(c) Plastic
(d) Clay
Answer:
(d) Clay

Question 2
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object ?
(a) Between the principal focus and the centre of curvature
(b) At the centre of curvature
(c) Beyond the centre of curvature
(d) Between the pole of the mirror and its principal focus.
Answer:
(d) Between the pole of the mirror and its principal focus.

Question 3
Where should an object be placed in front of a convex lens to get a real image of the size of the object ?
(a) At the principal focus of the lens (b) At twice the focal length
(c) At infinity
(d) Between the optical centre of the lens and its principal focus.
Answer:
(b) At twice the focal length.

Question 4
A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to be :
(a) Both concave.
(b) Both convex.
(c) the mirror is concave and the lens is convex.
(d) the mirror is convex, but the lens is concave.
Answer:
(a) Both concave

Question 5
No matter how far you stand from mirror, your image appears erect. The mirror is likely to be
(a) plane
(b) concave
(c) convex
(d) either plane or convex.
Answer:
(d) Either plane or convex.

Question 6
Which of the following lenses would you prefer to use while reading small letters found in a dictionary ?
(a) A convex lens of focal length 50 cm.
(b) A concave lens of focal length 50 cm.
(c) A convex lens of focal length 5 cm.
(d) A concave lens of focal length 5 cm.
Answer:
(c) A convex lens of focal length 5 cm.

Question 7
We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror ? What is the nature of the image ? Is the image larger or smaller than the object ? Draw a ray diagram to show the image formation in this case.
Answer:
A concave mirror gives an erect image when the object is placed between the focus F and the pole P of the concave mirror, i.e., between 0 and 15 cm from the mirror. The image thus formed will be virtual, erect and larger than the object.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q7

Question 8
Name the type of mirror used in the following situations.
(a) Headlights of a car.
(b) Side/rear-view mirror of a vehicle.
(c) Solar furnace.
Support your answer with reason.
Answer:
(a) Concave mirrors are used as reflectors in headlights of cars. When a bulb is located at the focus of the concave mirror, the light rays after reflection from the mirror travel over a large distance as a parallel beam of high intensity.

(b) A convex mirror is used as a side/rear-view mirror of a vehicle because

  • A convex mirror always forms an erect, virtual and diminished image of an object placed anywhere in front it.
  • A convex mirror has a wider field of view than a plane mirror of the same size.

(c) Large concave mirrors are used to concentrate sunlight to produce heat in solar furnaces.

Question 9
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object ? Verify your answer experimentally. Explain your observations.
Answer:
A convex lens forms complete image of an object, even if its one half is covered with black paper. It can be explained by considering following two cases.
Case I : When the upper half of the lens is covered
In this case, a ray of light coming from the object will be refracted by the lower half of the lens. These rays meet at the other side of the lens to form the image of the given object, as shown in the following figure.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q9

Case II: When the lower half of the lens Is covered
In this case, a ray of light coming from the object is refracted by the upper half of the lens. These rays meet at the other side of the lens to form the image of the given object, as shown in the given figure.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q9.1

Question 10
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
Answer:
Here : Object distance, u= -25 cm,
Object height, h = 5 cm,
Focal length, f = +10 cm
According to the lens formula, 1f=1ν−1u , we have
⇒ 1ν=1f−1u=110−125=15250orν=25015=16.66cm
The positive value of v shows that the image is formed at the other side of the lens.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q10
The negative value of image height indicates that the image formed is inverted.
The position, size, and nature of image are shown alongside in the ray diagram.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q10.1

Question 11
A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens ? Draw the ray diagram.
Solution:
Focal length, f = -15 cm, Image distance, ν = -10 cm (as concave lens forms the image on the same side of the lens)
From the lens formula 1f=1ν−1u , we have
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q11
Object distance, u = -30 cm
The negative value of u indicates that the object is placed in front of the lens.

Question 12
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
Solution:
Object distance, u = -10 cm, Focal length, f = +15 cm, Image distance, ν = ?
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q12
Thus, image distance, ν = + 6 cm
Because ν is +ve, so a virtual image is formed at a distance of 6 cm behind the mirror.
Magnification, m=−υu=−6−30=15 (i.e. < 1)
The positive value of m shows that image erect and its value, which is less than 1, shows that image is smaller than the object. Thus, image is virtual, erect and diminished.

Question 13
The magnification produced by a plane mirror is +1. What does this mean ?
Answer:
Since magnification, m=h‘h=−νu. Given, m = +1, so h’ = h and ν = -u

(i) m = 1 indicates the size of image is same as that of object.
(ii) positive sign of m indicates that an erect image is formed.

The opposite signs of ν and u indicate that image is formed on the other side of the mirror from where the object is placed i.e., image is formed behind the mirror and thus image formed is virtual.

Question 14
An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.
Solution:
Since object size, h = +5 cm,
object distance, u = -20 cm
and radius of curvature, R = +30 cm
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q14
A virtual, erect image of height 2.2 cm is formed behind the mirror at a distance of 8.6 cm from the mirror.

Question 15
An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focussed image can be obtained ? Find the size and the nature of the image.
Answer:
Here, object size, h = +7.0 cm,
object distance, u = -27 cm
and focal length, f = -18 cm
Image distance, ν = ?
and image size, h’ = ?
From the mirror formula, 1f=1ν−1u, we have
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q15
The screen should be placed at a distance of 54 cm on the object side of the mirror to obtain a sharp image.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q15.1
The image is real, inverted and enlarged in size.

Question 16
Find the focal length of a lens of power -2.0 D. What type of lens is this ?
Answer:
Here, P = -2.0 D
The type of lens is concave because the focal length is negative.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q16

Question 17
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging ?
Answer:
Here, P = +1.5 D
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Chapter End Questions Q17
Because the focal length is positive, the prescribed lens is converging.

NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction

Reflection of light by curved surfaces; Images formed by spherical mirrors, center of curvature, principal axis, principal focus, focal length, mirror formula (Derivation not required), magnification.
Refraction; laws of refraction, refractive index.
Refraction of light by spherical lens; Image formed by spherical lenses; Lens formula (Derivation not required); Magnification. Power of a lens;

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 10
Chapter NameLight Reflection and Refraction
Number of Questions Solved31
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Page 168

Question 1.
Define the principal focus of a concave mirror?
Answer:
Light rays that are parallel to the principal axis of a concave mirror converge at a specific point on its principal axis after reflecting from the mirror. This point is known as the principal focus of the concave mirror.

Question 2.
The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
Answer:
Radius of curvature, R = 20 cm
Radius of curvature of a spherical mirror = 2 x Focal length (f)
f = R/2 = 20/2 =10cm

More Resources for CBSE Class 10

Question 3.
Name the mirror that can give an erect and enlarged image of an object.
Answer:
When an object is placed between the pole and the principal focus of a concave mirror, the image formed is virtual, erect, and enlarged.

Download NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction PDF

Question 4.
Why do we prefer a convex mirror as a rear-view mirror in vehicles?
Answer:
Convex mirrors give a virtual, erect, and diminished image of the objects placed in front of them. They are preferred as a rear-view mirror in vehicles because they give a wider field of view, which allows the driver to see most of the traffic behind him.

Page 171

Question 1. Find the focal length of a convex mirror whose radius of curvature is 32 cm.
Answer: Radius of curvature, R = 32 cm
Radius of curvature = 2 x Focal length (f)
R = 2f
f = R/2 = 32/2 = 16cm
Hence, the focal length of the given convex mirror is 16 cm.

Question 2.
A concave mirror produces three times magnified (enlarged) real image of object placed at 10 cm in front of it. Where is the image located?
Answer:
Given, u = – 10 cm
Since image is real inverted so, m = -3
m = -v / u
⇒  -3 = -v/ -10
v= – 30 cm
Negative sign indicates the image will be real and image is formed at 30 cm in front of the mirror.

Page: 176

Question 1.
A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?
Answer:
The light ray bends towards the normal. When a ray of light travels from an optically rarer medium to an optically denser medium, it gets bent towards the normal. Since water is optically denser than air, a ray of light travelling from air into the water will bend towards the normal.

Question 2.
Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 108 m/s.
Answer:
Refractive index of a medium nm is given by,
Refractive index of a medium nm is given by,

Question 3.
Find out, from Table, the medium having highest optical density. Also find the medium with lowest optical density.
Answer:
NCERT Solutions for Class 10th Science Chapter 10
Highest optical density = Diamond
Lowest optical density = Air
Optical density of a medium is directly related with the refractive index of that medium. A medium which has the highest refractive index will have the highest optical density and vice-versa.
It can be observed from table 10.3 that diamond and air respectively have the highest and lowest refractive index. Therefore, diamond has the highest optical density and air has the lowest optical density

Question 4.
You are given kerosene, turpentine and water. In which of these does the light travel fastest?
Answer:
NCERT Solutions for Class 10th Science Chapter 10
The light can travel fast through water.

Question 5.
The refractive index of diamond is 2.42. What is the meaning of this statement?
Answer:
Refractive index of a medium nm is related to the speed of light in that medium v by the relation:

Where, c is the speed of light in vacuum/air
The refractive index of diamond is 2.42. This suggests that the speed of light in diamond will reduce by a factor 2.42 compared to its speed in air.

Page 184

Question 1.
Define one dioptre of power of a lens?
Answer:
One dioptre is the power Of a lens Of focal length 1m.
Power of lens is defined as the reciprocal of its focal length. If P is the power of a lens of focal length F in metres, then
P = 1/ f (in meters)
The S.I. unit of power of a lens is Dioptre. It is denoted by D.
1 dioptre is defined as the power of a lens of focal length 1 metre.
1 D = 1 m−1

Question 2.
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the lens if the image is equal to the size of the object? Also find the power of the lens.
Answer:
v = + 50 cm
Since image is real and of same size. The position of image should be double the focal length.
Hence, the object should be at 2f.
V = 2f = 50, f = 25 cm.
Power = 1/f = 100/25 = 4D

Question 3.
Find the power of a concave lens of focal length 2 m.
Answer:
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 184 Q3

Question 1.
Which one of the following materials cannot be used to make a lens?
(a) Water (b) Glass
(c) Plastic (d) Clay
Answer: (d) Clay

Question 2.
The ¡mage formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?
(a) Between the principal focus and the centre of Curvature
(b) At the centre of curvature
(c) Beyond the centre of curvature
(d) Between the pole of the mirror and Its principal focus.
Answer: (d) Between the pole of the mirror and its principal focus.

Question 3.
Where should an object b. placed In front of a convex lens to get a real
image of the size of the object?
(a) At the principal focus of the lens
(b) At twice the focal length
(c) At infinity
(d) Between the optical centre of the lens and its principal focus
Answer:
(b) At twice the focal length

Question 4.
A spherical mirror and a thin spherical lens have each a focal length of 15 cm. The mirror and the lens are likely to be:
(a) both concave
(b) both convex
(c) the mirror is concave, but the lens is convex
(d) the mirror is convex, but the lens is concave
Answer:
(a) Both concave.

Question 5.
No matter how far you stand from a mirror, your Image appears erect. The mirror is likely to be
(a) plane
(b) concave
(c) convex
(d) Either plane or convex
Answer:
(d) Either plane or convex.

Question 6.
Which of the following lenses would you prefer to use while reading small letters found ¡n a dictionary?
(a) A convex lens of focal length 50cm
(b) A concave lens of focal length 50cm
(c) A convex lens of focal length 5 cm
(d) A concave lens of focal length 5 cm.
Answer:
(c) A convex lens of focal length 5 cm.

Question 7.
We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. what should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this
case.
Answer:
We are given the focal length cf the concave mirror as f = -15cm.
For getting an erect image using a concave mirror, the object should be placed at a distance less than the focal length.
i.e. 15 cm from the pole. The image formed will be virtual, enlarged and erect.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q7

Question 8.
Name the type of mirror used in the following situations.
(a) Headlights of a car
(b) Side/rear-view mirror of a vehicle
(c) Solar furnace
Support your answer with reason.
Answer:
(a) Concave mirror, to get powerful and parallel beams of light.
(b) Convex mirror because it always gives an erect image and enables the driver to view much larger area.
(c) Concave or parabolic mirror because it can concentrate sunlight at the focus to produce heat in the solar furnace.

Question 9.
One half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Answer:
Yes, even when one half of the lens is covered with a black paper, complete image of the object will be formed. Take a convex lens and focus the light from a distant object onto a screen. As expected an image (sharp) is formed at a distance equal to the focal length Cover the lower or the upper half of the lens and focus the light from the same object onto the same screen. You will be able to get a sharp image again; however the brightness of the image will be less in the second case. The same effect w,ll be seen even if the lens is half covered with black strips.

Question 10.
An object 5cm in length is held 25cm away from a converging lens of focal length 10 cm. Draw a ray diagram and find the position, size and the nature of the image formed.
Answer:
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q10
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q10.1
Therefore, the mage ¡s formed between F2 and 2F2 on the other side of the lens. It is real and inverted, and smaller in size than the object.

Question 11.
A concave lens of focal length 15 cm forms an ¡mage 10 cm from the lens. How far is the object placed from the Pens? Draw the ray diagram.
Answer:
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q11

Question 12.
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the ¡mage.
Answer:
f = +15 cm. u = -1o cm
For mirror, we have
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q12
The image must be virtual and erect.

Question 13.
The magnification produced by a plane mirror is +1. What does this mean?
Answer:
This means that size of the image is equal to the size of the object.

Question 14.
An object 5.0 cm in length Is placedat a distanc, of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image nature and size.
Answer:
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q14

Question 15.
An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.
Answer:
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q15

Question 16.
Find the focal length of a lens of power -2.0 D. What type of lens is this?
Answer:
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q16

Question 17.
A doctor has prescribed a corrective lens of power +1.5 D. find the focal length of the lens. Is the prescribed lens diverging or converging?
Answer:
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction Page 187 Q17

Multiple Choice Questions (MCQs) [1 mark each]

Question 1.
Hold a highly polished steel spoon curved inwards close to your face and move it slowly away from your face. What will you observe?
(a) Enlarged and erect image of your face
(b) Smaller and inverted image of your face
(c) Smaller and erect image of your face
(d) Enlarged and inverted image of your face
Answer:
(b) The inner curved surface of a highly polished steel spoon acts as a concave mirror. When the spoon is at a small distance from the face such that, the object lies between pole and focus of concave mirror, so an enlarged and erect image of your face will be observed but as the spoon is slowly moved away from the face, the image becomes smaller and appears inverted.

Question 2.
Which one of the following materials cannot be used to make a lens? [NCERT]
(a) Water
(b) Glass
(c) Plastic
(d) Clay
Answer:
(d) Clay can never be transparent, so it cannot be used to make lens.

Question 3.
No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be [NCERT]
(a) plane
(b) concave
(c) convex
(d) either plane or convex
Answer:
(d) Plane mirrors and convex mirrors always form the erect images.

Question 4.
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object? [NCERT]
(a) Between principal focus and centre of curvature
(b) At centre of curvature
(c) Beyond centre of curvature
(d) Between pole of the mirror and its principal focus
Answer:
(d)

Question 5.
An object AB is placed in front of a convex lens at its centre of curvature as shown in figure below.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q5
Four students traced the path of light ray after refraction through the lens. Which one of them is correct?
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q5.1
(a) Only I
(b) Only II
(c) Only III
(d) Only IV
Answer:
(d) When the object is placed at centre of curvature (2Fx) of convex lens, the same sized image is formed at 2F2. The image formed is real and inverted.

Question 6.
A spherical mirror and a thin spherical lens have each of a focal length -15 cm. The mirror and lens are likely to be [NCERT]
(a) both concave
(b) both convex
(c) mirror is concave and lens is convex
(d) mirror is convex and lens is concave
Answer:
(a) The focal length is taken as negative for both concave mirror and concave lens.

Question 7.
Which of the following can make a parallel beam of light when light from a point source is incident on it? [NCERT Exemplar]
(a) Concave mirror as well as convex lens
(b) Convex mirror as well as concave lens
(c) Two plane mirrors placed at 90° to each other
(d) Concave mirror as well as concave lens
Answer:
(a) A ray passing through the principal focus of a concave mirror or convex lens, after reflection/refraction, will emerge parallel to the principal axis.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q7

Question 8.
Under which of the following conditions, a concave mirror can form an image larger than the actual object? [NCERT Exemplar]
(a) When an object is kept at a distance equal to its radius of curvature
(b) When an object is kept at a distance less than its focal length
(c) When an object is placed between the focus and centre of curvature
(d) When an object is kept at a distance greater than its radius of curvature
Answer:
(c) A concave mirror can form an image enlarged, real and inverted than the actual object, beyond centre of curvature (C) when object is placed between the focus (F) and centre of curvature.

Question 9.
A light ray enters from medium A to medium Bas shown in the figure. The refractive index of medium B relative to A will be [NCERT Exemplar]
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q9
(a) greater than unity
(b) less than unity
(c) equal to unity
(d) zero
Answer:
(a) Since, light rays in the medium B goes towards normal. So, it has greater refractive index and lesser velocity of light w.r.t. medium A. So, refractive index of medium B w.r.t. medium A is greater than unity.

Question 10.
Figure shows a ray of light as it travels from medium A to medium B. Refractive index of the medium B relative to medium A is
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q10
Answer:
(a) Given, angle of incidence, i = 60°, angle of refraction, r = 45°
Refractive index of the medium B relative to medium A,
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q10.1

Question 11.
Beams of light are incident through the holes A and B and emerge out of box through the holes C – and D respectively, as Box shown in the figure.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q11
Which of the following could be inside the box? [NCERT Exemplar]
(a) A rectangular glass slab
(b) A convex lens
(c) A concave lens
(d) A prism
Answer:
(a) Here, the emergent rays are parallel to the direction of the incident ray. Therefore, a rectangular glass slab could be inside the box as the extent of bending of light ray at the opposite parallel faces AB (air-glass interface) and CD (glass-air interface) of the rectangular glass slab are equal and opposite. This is why the ray emerges parallel to the incident ray.

Question 12.
A beam of light is incident through the holes on side A and emerges out of the holes on the other face of the box as shown in the figure. Which of the following could be inside the box? [NCERT Exemplar]
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q12
(a) Concave lens
(b) Rectangular glass slab
(c) Prism
(d) Convex lens
Answer:
(d) Since, in the figure all the parallel rays converge at a point. So, inside the box there must be a convex lens.
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q12.1

Question 13.
Which of the following statement is true? [NCERT Exemplar]
(a) A convex lens has 4D power having a focal length 0.25 m
(b) A convex lens has 4D power having a focal length -0.25 m
(c) A concave lens has 4D power having a focal length 0.25 m
(d) A concave lens has 4D power having a focal length -0.25 m
Answer:
(a) The power P of a lens of focal length f is given by
P = 1/f, where f is the focal length in metre and P is the power in dioptre.
P= 1/f or f = 1/P = 1/4 = 0.25 m

Question 14.
Magnification produced by a rear view mirror fitted in vehicles [NCERT Exemplar]
(a) is less than one
(b) is more than one
(c) is equal to one
(d) can be more than or less than one depending upon the position of the object in front of it.
Answer:
(a) The convex mirror forms virtual, erect and diminished image of the object and rear view mirror also form same type of image. Therefore, magnification (m) produced by a rear view mirror fitted in vehicles is less than one, i.e. m < 1.

Question 15.
Rays from the Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed, so that size of its image is equal to the size of the object? [NCERT Exemplar]
(a) 15 cm in front of the mirror
(b) 30 cm in front of the mirror
(c) between 15 cm and 30 cm in front of the mirror
(d) more than 30 cm in front of the mirror
Answer:
(b) The rays from the Sun, i.e. from infinity, are parallel to principal axis after reflection converge at a point is known as focus. Therefore, focal length if) of concave mirror is 15 cm. And we know that, same size, real and inverted image is formed by concave mirror when object is placed at focus 2 A or centre of curvature, so to form same size of image, object will be placed at 15 x 2 =30 cm.

Question 16.
The path of a ray of light coming from air passing through a rectangular glass slab traced by four students shown as I, II, III and IV in the figure. Which one of them is correct? [NCERT Exemplar]
NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction MCQs Q16
(a) Only I
(b) Only II
(c) Only III
(d) Only IV
Answer:
(b) In a rectangular glass slab, the emergent rays are parallel to the direction of the incident ray, because the lateral deviation of bending of the ray of light at the opposite parallel faces (air-glass interface) and (glass-air interface) of the rectangular glass slab are equal and opposite. This is why the ray emerges are parallel to the incident ray.

Question 17.
You are given water, mustard oil, glycerine and kerosene. In which of these media, a ray of light incident obliquely at same angle would bend the most? [NCERT Exemplar]
(a) Kerosene
(b) Water
(c) Mustard oil
(d) Glycerine
Answer:
(d) The given material having their refractive index as kerosene is 1.44, water is 1.33, mustard oil is 1.46 and glycerine is 1.74. Thus, glycerine is most optically denser and hence have the largest refractive index. Therefore, ray of light bend most in glycerine.

Question 18.
A student placed a light bulb in midway between the two plane mirrors inclined at an angle of 60°. How many images will be observed by him?
(a) 4
(b) 6
(c) 5
(d) 8
Answer:
(c) Number of images formed by two plane mirrors inclined at an angle 60° when a light bulb is placed in midway between them is
N = 360°/60° – 1 = 6 – 1 = 5

Question 19.
Where should an object be placed in front of a convex lens to get a real image of the size of the object? [NCERT]
(a) At the principal focus of the lens
(b) At twice the focal length
(c) At infinity
(d) Between the optical centre of the lens and its principal focus
Answer:
(b) To set the real image of the size of the object, it should be placed at twice the focal length of a convex lens.

Question 20.
Which of the following lenses would you prefer to use while reading small letters found in dictionary? [NCERT]
(a) A convex lens of focal length 50 cm
(b) A concave lens of focal length 50 cm
(c) A convex lens of focal length 5 cm
(d) A concave lens of focal length 5 cm
Answer:
(c) Convex lens is used as magnifying glass. For better performance its focal length should be small.

NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction (Hindi Medium)

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Class 10 Science Light Reflection and Refraction Mind Map

LIGHT REFLECTION & REFRACTION
Form of energy produces the sensation of vision in eyes. Light (EM waves wave-length 400 nm to 750 nm).
The path of light (always travel in straight line) is ray of light

Characteristics of light

  • Rectilinear propagation of light
  • Light travels with a speed of 3 × 108 m/s in air/vaccum.
  • Speed of light depends on the medium
  • Light shows behaviour such as reflection, refraction, interference, diffraction, polarisation etc.

Law of Refraction
Refraction of light: Bending of light ray while passing from one medium to another medium

  • A ray of light bends towards the normal, while going from rarer to denser medium
  • And bends away from the normal while going from denser to rarer medium
  • Refraction of light takes place because the speed of light is different in the two media

Total internal Reflection : Ray totally reflected back to denser medium
Phenomena based on TIR

  • Mirage – optical illusion in deserts
  • Looming – optical illusion in cold countries
  • Optical fibre
  • Brilliance of diamond

Necessary conditions for TIR
(i ) Ray of light must travel from denser to rarer medium
(ii) ∠i > ∠c for two media

Critical angle (c) Angle i in denser medium for which angle of refraction in rarer medium is 90° μ = 1sinC

Snell’s law
μ = sinisinr
For two media
1μ2 = μ2μ1=sinisinr

Reflection of light: Turning back of light in the same medium after striking the reflecting surface or mirror

  • After reflection, velocity, frequency and wavelength of light remains same but intensity decreases
  • If reflection takes place from denser medium then phase change ‘π’

Regular Reflection

Reflection on smooth surface.

Diffuse Reflection
Reflection on rough surface.

Laws of Reflection

The incident ray the normal and the reflected ray all lie in the same plane The angle of incidence (i) is always equal to angle of reflection (r) i.e., ∠i = ∠r

Mirror formula
1f=1u+1v
When two plane mirrors are held at an angle 9 with their reflecting surfaces facing each other and an object is placed between them, images are formed by successive reflections. .
fconcave = negative
fconvex = positive
and fplane = ∞

Relation between focal length (f) and radius of curvature, R
f = R2

Magnification
m = vu= height of image  height of object 
m = ff−u=f−vf

The incident ray, the normal and the refracted ray all lie in the same plane
Refractive index,
μ = cv= real depth  apparent depth 

Plane Mirror

Is a looking glass, highly polished on one surface.

  • Forms virtual and erect image
  • Distance of object from mirror = distance of image from mirror.
  • The size of the image is same as object.
  • Image is laterally inverted.
  • Used in kaleidoscope periscope, etc.

Concave Mirror
Spherical glass polished on the outside. It is also known as a converging mirror.

  • Images produced are always real, inverted, can be enlarged based on the position except when object is placed between pole and focus.
  • Uses: Make-up and shaving mirrors, dentist mirror, in floodlight etc.

Image formation by a convex mirror for different positions of the object

‘‘Position of the object”“Position of the image”“Size of the image”“Nature of the image”
Anywhere between Between Pole(P) and infinity (∞)Between P and F back of the mirrorSmallVirtual and erect
At infinityAt FVery small in sizeVirtual and erect

Convex Mirror
Spherical glass polished inside. It is also known as diverging mirror.

  • It forms virtual, upright and small images.
  • Uses: for security’ purposes, in vehicles as rear- view mirror and street lighting.

Image formation by a concave mirror for different positions of the object

“Position of the object”“Position of the image”“Size of the image”“Nature of the image”
At infinityAt the focus FHighly -diminished, point-sizedReal and inverted
BeyondCBetween F and C’DiminishedReal and inverted
At CAt CSame sizeReal and inverted
B/W C and FBeyond CEnlargedReal and inverted
At FAt infinityHighly enlargedReal and inverted
B/W P and FBehind the mirrorEnlargedVirtual and erect

Atmospheric Refraction

Earth’s atmosphere is thin at the top and dense at the bottom, thus leads to refraction of light,
μ = c/v

  • Twinkling of stars
  • Rainbow
  • Advanced sunrise and delayed sunset

Refraction Through a Glass Slab
x = tsin(i−r)cosr
∴ x ∝ μ

Power of a lens

P = 1f( in metre )
Unit of power of lens is diopter (D)
Pconvex → Positive
Pconcave → Negative
and Pplane → Zero

Lens
Piece of transparent material with two refracting surfaces, at least one is curved and refractive index should different as that of the surrounding.

Lens formula
1f=1v−1ufconvex → negative
fconcave → positive
and fplane → ∞

Concave Lens
Cental portion of lens is thinner than marginal. It as also known as diverging lens.

Convex Lens
Central portion of lens is thicker than marginal. It is also known us converging lens.

Magnification
Ratio of distance of image to the distance of object from the optical centre. Also equal to height of image to the height of object
m = Io=vu=hIho

Nature, position and relative size of the image formed by a concave lens for various position of the object

‘‘Position of the object”“Position of the image”Relative Size of the image”“Nature of the image”
At infinityAt focus F1Highly-diminished, point-sizedVirtual and erect
Between infinity and Optical centre O of the lensBetween F1 and Optical centre ODiminishedVirtual and erect

Nature, position and relative size of the image formed by a convex lens for various positions of the object

Position of the objectPosition of the imageRelative size of the imageNature of the image
At infinityAt focus F2Highly -diminished, point-sizedReal and inverted
Beyond 2F1Between F2 and 2F2DiminishedReal and inverted
At 2F1At 2F2Same sizeReal and inverted
Between F1 and 2F1Beyond 2F2EnlargedRea! and inverted
At Focus F1At infinityInfinitely large or highly enlargedReal and inverted
Between F1and Optical centre OOn the same side of the lens as the objectEnlargedVirtual and erect

Now that you are provided all the necessary information regarding NCERT Solutions For Class 10 Science Chapter 10 Light Reflection and Refraction and we hope this detailed article on light reflection and refraction class 10 NCERT solutions is helpful. If you have any questions related to this article, kindly ask your questions through the comment section below and we will get back to you as soon as possible.

NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution

NCERT Solutions For Class 10 Science Chapter 9 Heredity and Evolution: In this article, we will provide you detailed NCERT Solutions For Class 10 Science Chapter 9 Heredity and Evolution. These heredity and evolution class 10 exercise answers were prepared by the best faculty in India to score good marks in the subject Science.

Also working on NCERT Solutions For Class 10 Science Chapter 9 will give you a strong foundation on the competitive exams like JEE, NEET, UPSC, etc., Read on to find out everything about NCERT Solutions For Class 10 Science Chapter 9 Heredity and Evolution.

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 9 Heredity and Evolution, let’s have an overview of the list of topics and subtopics under class 10 biology heredity and evolution NCERT solutions:

  1. Heredity And Evolution
  2. Accumulation Of Variation During Reproduction
  3. Heredity
    1. Inherited Traits
    2. Rules for the Inheritance of Traits – Mendel’s Contributions
    3. How do these traits get Expressed
    4. Sex Determination
  4. Evolution
    1. An Illustration
    2. Acquired and Inherited Traits
  5. Speciation
  6. Evolution And Classification
    1. Tracing Evolutionary Relationships
    2. Fossils
    3. Evolution by Stages
  7. Evolution Should Not Be Equated With ‘Progress’
    1. Human Evolution

Free download NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 9 Intext Questions

Page Number: 143

Question 1.
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier ?
Answer:
Trait B, because it is present in more members of the population. It is likely to have arisen earlier and has now spread to 60% of the population. Trait A is new and has spread to only 10% of the population.

Question 2.
How does the creation of variations in a species promote survival ?
Answer:
The variations provide stability to the population of various species by preventing them from getting wiped out during adverse conditions.
The natural environment also changes, and variations in species which become suited to the environment help it to survive.

Page Number: 147

Question 1.
How do Mendel’s experiments show that traits may be dominant or recessive ? [AICBSE 2015]
Answer:
Mendel took pea plants with contrasting characteristics tall plant and dwarf (or short) plant. On cross pollination, he got all tall plants in first generation (F1). But by the self¬pollination of F1 tall plants, the plants of second generation consisted of tall and short pants in the ratio of 3 : 1. On the basis of these experiments, the characteristics appeared in first generation were called dominant (i.e. tall plants) and the characteristics that did not appear were called recessive (dwarf i.e. plants).

Question 2.
How do Mendel’s experiments show that traits are inherited independently ? [AICBSE 2015]
Answer:
Mendel took two pairs of alternate expression of two traits and carried out dihybrid crosses by crossing them. The traits appeared in first generation were termed as dominant. When he used these F1 progeny to generate F2 progeny by self-pollination plants of different types were produced. In some plants both the traits were dominant, while in some plants both were recessive and some plants exhibited mixed traits. This indicates that traits are inherited independently.

Question 3.
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant ? Why or why not ?
Answer:
This information is not enough. This is because each individual is carrying two alleles. The recessive trait can occur only when who alleles are similar. It blood group A is dominant and O is recessive, then daughter can have blood group O only when both recessive alleles occur together in mother, and father has one allele of O and other of A.

Question 4.
How is the sex of the child determined in human beings ?
OR
“The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it.” Justify this statement with the help of a flow chart showing determination of sex of a newborn. [CBSE (Delhi) 2013]
Answer:
Half of the male gametes (sperms) carry X chromosome and other half carry Y chromosomes. All the female gametes carry only X chromosomes. When a sperm fertilizes an egg, the following situations become possible.

  1. (i) When a sperm carrying X chromosome fertilises an egg that contains only X chromosome), the resulting zygote develops into a female (XX condition).
  2. (ii) When a sperm carrying Y chromosome fertilises an egg (that contains only X chromosome), the resulting zygote develops into a male (XY condition).

Thus there are 50 – 50 chances of a male or female child and none of the parents may Sex determination in humans be considered responsible for it.
The sex-determination mechanism is shown alongside.
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Intext Questions Page 147 Q4

Page Number: 150

Question 1.
What are the different ways in which individuals with a particular trait may increase in a population ?
Answer:
Different ways in which individuals with a particular trait may increase in a population are as follow :

  1. If it gives the benefit of survival through natural selection.
  2. Due to a sudden increase in a particular trait in a population, i.e., by genetic drift.

Question 2.
Why are traits acquired during the life-time of an individual not inherited ?
Answer:
The traits acquired during the life-time are changes in the non-reproductive cells of the organisms and are not capable of being passed on to the next generation.

Question 3.
Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics ?
Answer:
The small numbers of surviving tigers are a cause of worry from the point of view of genetics because in tigers there are negligible genetic variations. Due to this they are not well adapted. The rapid environmental changes cannot be favouable for them. If these changes are not controlled, tigers would be wiped out.

Page Number: 151

Question 1.
What factors would lead to the rise of a new species ?
Answer:
The factors that would lead to the rise of a new species are the following :

  1. Geographical isolation of a population caused by various types of barriers (such as mountain ranges, rivers and sea). The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of pupulation.
  2. Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.
  3. Variations caused in individuals due to a natural selection.

Question 2.
Will geographical isolation be a major factor in the speciation of a self- pollinating plant species ? Why or why not ?
Answer:
The geographical isolation cannot be major factor in the speciation of a self-pollinating plant species because it does not have to look the plants for its process of reproduction to be carried out.

Question 3.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Why or why not ?
Answer:
Geographical isolation cannot be a major factor in the speciation of an asexually reproducing organism because it does not require any other organism to carry out reproduction.

Page Number: 156

Question 1.
Give an example of characteristics being used to determine how close two species are in evolutionary terms.
Answer:
If similar characteristics are shown in different organisms, then these are considered to be inherited from the common ancestry. It also shows the closeness of the species.
For example, bats and birds have some similarity in their wings, so they are closely related, while lizard and squirrel do not have wings so these are not closely related to the birds and bats.

Question 2.
Can the wing of a butterfly and the wing of a bat be considered homologous organs ? Why or why not ?
Answer:
The wings of a butterfly and the wings of a bat cannot be considered to be homologous organs because they have different basic designs though they are used for the same purpose of flying. They are analogous organs.

Question 3.
What are fossils ? What do they tell us about the process of evolution ?
Answer:
Fossils : Fossils are the remains or traces of a dead organism. These are formed through the formation of sedimentary rocks. They provide following information on the process of evolution.

  1. They tell about the changes that occured on the earth’s surface and the corresponding organisms.
  2. They tell about the gradual development of complex structured organisms from simple structured organisms.
  3. It is known through them that birds are evolved from reptiles.
  4. They state that angiosperms are developed from pteriodophytes and gymnosperms.
  5. They exhibit the process of humana evolution.

Page Number: 158

Question 1.
Why are human beings who look so different from each other in terms of size, colour and looks said to belong to the same species ?
Answer:
This is because although genetic make up of humans may be slightly different in different races of people, there is no reproductive isolation. Reproductive isolation differentiates one species from the other. Human beings different in size, colour and looks can marry among themselves and produce fertile offspring.

Question 2.
In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better’ body design ? Why or why not ?
Answer:
Bacteria is a primitive organism as they came into being very early in evolution. But these organisms are still surviving in the present conditions after millions of years. This is because they have adapted well to the changing environment over these years. Same is the case for all other organisms like spiders, fishes and chimpanzees which have adapted to their environment and have survived. Therefore, all the organisms which exist have a body design which is better as it is suited to their environment.

NCERT Solutions for Class 10 Science Chapter 9 Textbook Chapter End Questions

Question 1.
A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short.
This suggests that the genetic make-up of the tall parent can be depicted as:
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
Answer:
(c) TtWW

Question 2.
An example of homologous organs is :
(a) our arm and a dog’s fore-leg
(b) our teeth and an elephant’s tusks
(c) potato and runners of grass
(d) all of the above
Answer:
(d) All of the above

Question 3.
In evolutionary terms, we have more in common with :
(a) a Chinese school-boy
(b) a chimpanzee
(c) a spider
(d) a bacterium
Answer:
(a) A Chinese school-boy

Question 4.
A study found that children with light coloured eyes are likely to have parents with light coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive ? Why or why not ?
Answer:
This information is not complete. On the basis of this, it cannot be decided light colour trait is dominant or recessive. So it cannot be said until one does not know the nature of this trait in the parents.

Question 5.
How are the areas of study-evolution and classification interlinked ?
OR
‘Two areas of study namely ‘evolution’ and ‘classification’ are interlinked”. Justify this statement. [AICBSE 2016]
Answer:
Classification of organisms is based on relative similarities and differences among organisms. Resemblances in organisms are because they have arisen from a common ancestor and differences in them are due to adaptations to different types of environment. Since the organisms can be graded in order of increasing complexity it indicates at the concept of evolution.

Question 6.
Explain the terms analogous and homologous organs with examples. [CBSE 2011,2013, 2014]
Answer:
Analogous organs : Those organs which have different basic structure (or different basic design) but have similar appearance and perform similar functions are called analogous organs.
For example, The wings of an insect and a bird are analogous organs.

Homologous organs :  Those organs which have the same basic structure (or same basic design) but different functions are called homologous organs.
For example, The wing of a bat, flipper of a seal, front leg of a horse and arm of a man are homologous organs.

Question 7.
Outline a project which aims to find the dominant coat colour in dogs.
Answer:
Suppose a black homozygous male is mated with a white homozygous female. If the progeny has all black dogs then the dominant coat colour is black.

Question 8.
Explain the importance of fossils in deciding evolutionary relationships.
Answer:
Fossils play important role in providing evolutionary evidences because by knowning the age of fossils we can know about the evolution process of an organism.
For example, a fossil bird called archaeopteryx that looked like a bird had many other features of reptiles. It had feathered wings like those of birds, but teeth and tail like those of reptiles. Archaeopteryx is, therefore, a connecting link between the reptiles and birds, and hence suggests that the birds have evolved from the reptiles.

Question 9.
What evidence do we have for the origin of life from inanimate matter ? [CBSE 2011, 2014]
Answer:
A British scientist J.B.S. Haldane at first in 1929 suggested that life is originated from inanimate matter. According to him life must have developed from the simple inorganic molecules which were present at that time. Later, Miller and Urey in 1953 presented its evidences. They assembled an apparatus to create an early earth atmosphere which was supposed to consist of gases like methane, ammonia and hydrogen sulphide, etc. over water. This was maintained at a temperature just below 100°C and electric sparks were then passed through the mixture of gases to stimulate lightning for about one week. At the end of one week, it was found that about 15 per cent of carbon (from methane) had been converted into simple compounds and amino acids which make up protein molecules formed in living organisms. This experiment provides the evidence that the life originated from inanimate matter (or lifeless matter) like inorganic molecules.
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Chapter End Questions Q9

Question 10.
Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually ? [CBSE 2011,2014]
Answer:
During sexual reproduction there is ‘crossing over’ of chromosomes, that gives rise to variations. These variations are inherited and increase the chances of survival of an organism.

  1. In sexual reproduction variations may occur due to errors in DNA copying.
  2. There may be variations due to interchange of homologous chromosomes during crossing over of male and female.
  3. In sexual reproduction, it is not predetermined that which gamete would fuse with another gamete. It depends only on chance. It is also a reason of variation.
    These variations enable the organisms to adapt themselves to the changing conditions and also help to give rise to new species.

Question 11.
How is the equal genetic contribution of male and female parents ensured in the progeny ? [CBSE 2011, 2013]
Answer:
Genetic material in most organisms is present in pairs of chromosomes. Gametes in the sexually reproducing organisms are formed by the process of meiosis during which half of the genetic material goes into each gamete. When the gametes from male and female parents fuse with each other during sexual reproduction, the normal complement is restored. Half of the genetic material comes from the female and half from the male.

Question 12.
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement ? Why or why not?
Answer:
Yes, variations that confer an advantage to an individual organism are inherited. The organism can survive longer in an environment and maintain its existence in the population.

NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution

Heredity and Evolution: Heredity; Mendel’s contribution- Laws for inheritance of traits, Sex determination : brief introduction; Basic concepts of evolution.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 9
Chapter NameHeredity and Evolution
Number of Questions Solved29
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Page 143

Question 1.
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% Of the same population, which trait is likely to have arisen earlier ?
Answer: As species are asexually reproducing, there would be only very minor differences generated due to small inaccuracies in DNA copying, so trait B, which exists in 60% of the same population may get inherited earlier while trait A, which exists in 10% of the population may be originated late due to variations. Thus, trait B have arisen earlier since it is present in 60% of the same population.

Question 2.
How does the creation of variations in a species promote survival ?
Answer: Natural selection selects the individuals having useful variations which ensure their survival in the prevailing conditions of environment. Variant individuals that can withstand or cope with prevailing environment will survive better and will increase in number through differential reproduction.

More Resources for CBSE Class 10

Page 147

Question 1.
How do Mendel’s experiments show that traits may be dominant or recessive ?
Answer:
Mendel took pea plants with contrasting characteristics – tall plant and dwarf (short) plant. On cross pollination, he got all tall plants in F1 generation. Then by self pollination of F1 tall plants, he produced second generation (F2) consisting of tall and short plants in the ratio of 3 : 1. Then he concluded that, ‘T’ (tall) trait is dominant while ‘t’ trait for shortness is recessive.

Download NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution PDF

Question 2.
How do Mendel’s experiments show that traits are inherited independently ?
Answer:
In a dihybrid cross made by Mendel, it was observed that when two pairs of traits or characters were considered; each trait expressed independent of the other. Thus, Mendel was able to propose the Law of Independent Assortment which says about independent inheritance of traits.

Question 3.
A man with blood group A marries a woman with blood O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O is dominant ? Why or why not ?

Answer:
No. This information is not sufficient to determine which of the traits − blood group A or O − is dominant. This is because we do not know about the blood group of all the progeny.Blood group A can be genotypically AA or AO. Hence, the information is incomplete to draw any such conclusion.

Question 4.
How is the sex of the child determined in human beings?
Sex determination in humans
Answer:
The females carry two X-chromosomes. Females produce one type of gametes (eggs) with same type of chromosomes (22 + X). Males have one X and one Y- chromosome. Among the male gametes, half of the sperms carry X-chromosome (22 X) and half
carry Y-chromosome (22 + Y). Thus, female is homogametic and male is heterogametic. When a sperm carrying X- chromosome fertilises an egg, the zygote develops into female (XX condition). When sperm carrying Y-chromosome fertilises an egg, the zygote develops into a male (XY condition). Thus, sex is determined at the time of fertilisation.

Page 150

Question 1.
What are the different ways in which individuals with a particular trait may increase in a population ?
Answer:
Different ways are : variation, natural selection and genetic drift (isolation).

Question 2.
Why are traits acquired during the lifetime of an individual not inherited ?
Answer:
Because acquired characters bring changes only in non-reproductive tissues and cannot change the genes of the germ cells. Thus, acquired traits cannot be passed to next generation.

Question 3.
Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics ?
Answer:
(i) If any natural calamity occurs and kills these small number of surviving tigers, they can become extinct resulting in the loss of some genes forever.
(ii) Small number will lead to little recombination and, therefore, lesser variations. These both are very important for giving better survival chances to the species.
(iii) Less number of species means lesser extent of diversity and lesser number Of traits which reduces the chances of adaptability with respect to the change in the environment.

Page 151

Question 1.
What factors could lead to the rise of a new species ?
Answer:
Genetic variations, natural selection and reproductive isolation could lead to the rise of a new species.

Question 2.
Will geographical isolation be a major factor in the speciation of a self-pollinating plant species ? Why or why not ?
Answer:
No, because pollination occurs on the same plant in self-pollinating plant species.

Question 3.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Why or why not ?
Answer:
No, because asexual reproduction involves single parent or organism.

Page 156

Question 1.
Give an example of characteristics being used to determine how close two species am in evolutionary terms ?
Answer:
Homologous organs, analogous organs and vestigial organs help to identify evolutionary relationships amongst the species.

Question 2.
Can the wing of butterfly and the wing of a bat be considered homologous organs ? Why or why not ?
Answer:
No, wing of a bat and wing of a bird cannot be considered as homologous organs because they have different basic structure.

Question 3.
What are fossils ? What do they tell us about the process of evolution ?
Answer:
Fossils are the impression or remains of ancient life found preserved in the sedimentary rocks. Fossils are direct evidences of evolution. Fossils also help to identify evolutionary relationship between apparently different species. They also tell about the extent of evolution that has taken place.

Page 158
Question 1.
Why are human beings who look so different from each other in terms of size, colour and looks said to belong to the same species ?
Answer:
They look different because of interaction of genes with environment which results in change in their appearance. But they belong to the same species as they have same number of chromosomes and can breed among themselves.

Question 2.
In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better body design’ why or why not ?
Answer:
No, because different designs are the product of evolution and different species have different body design to suit or adapt to their environment.

Page 159

Question 1.
A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing whfte flowers. The progeny all bore violet flowers, but almost half of them are short. This suggests that the genetic make-up of the tall parent can be depicted as
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
Answer:
(c) Genetic make-up of tall plant can be depicted by TtWW.

Question 2.
An example of homologous organs is
(a) our arm and a dogs fore-leg.
(b) our teeth and an elephants tusks.
(c) potato and runners of grass.
(d) All of the above.
Answer:
(d) Both organs in all options have same basic structural design but have different functions and appearance.

Question 3.
In evolutionary terms, we have more in common with
(a) a Chinese school-boy.
(b) a chimpanzee.
(c) a spider.
(d) a bacterium.
Answer:
(a) A Chinese school-bpy is also a human being.

Question 4.
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
Answer:
We can say that light eye colour trait is dominant because only dominant traits are expressed in the first generation.

Question 5.
How are the areas of study – evolution and classification— inteilinked?
Answer:
Evolution and classification are interlinked with each other in many ways. Classification is the most important term to explain evolution. It is based on the similarities and differences between two species or among two organisms. More closer the characteristics, the moe doser is the evolution and chances to be in the same group of classification. Thus, the classification of species is a reflection of their evolutionary relationship.

Question 6.
Explain the terms analogous and homologous organs with examples.
Answer:
Analogous organs are those organs which have different basic structural designs and developmental origins but have similar appearance and perform similar functions.
Examples:
Wings of an insect and wings of a bat.
Homologous organs are those organs which have the same basic structural design and developmenta’ origin but have different functions and appearance.
Examples: Forelimbs of frog and forelimbs of human.

Question 7.
Outline a project which alms to find the dominant coat colour in dogs.
Answer:
A homozygous black (RB) male dog and a homozygous white (bb) female dog is taken and given to mate and produce offspring in F1 generation. If black colour is dominant out of every 4 dogs, 3 will be black and if white colour is dominant 3 out of 4 dogs will be white.
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Page 159 Q7

Question 8.
Explain the importance of fossils in deciding evolutionary relationships.
Answer:
Fossils and their study is useful to know about the species which are no longer alive. They provide evidence and missing links between two classes. They are helpful in forming a sequence of organisms in the pathway of evolution. Thus, fossils have importance in deciding evolutionary relationships.

Question 9.
What evidence do we have for the origin of life from inanimate matter?
Answer:
Stanley L. Miller and Harold C. Urey provided evidence regarding origin of life from inanimate matter. They assembled an atmosphere similar to that existed on early earth. The atmosphere had molecules like ammonia, methane, hydrogen sulphide and water, but no oxygen. The mixture was maintained at a temperature just below 100◦C and sparks were passed through the mixture of gases. At the end of a week, 15% carbon from methane had been converted to simple compounds of carbon like aminoacids which make up protein molecules. So, life arose afresh on earth.

Question 10.
Explain how sexual reproduction gives rise to more viable variations that asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually ?
Answer:
Variations occurring during sexual reproduction may be due to:

  1. Separation of homologous chromosomes (by chance only) during gamete formation.
  2. Crossing over (recombination) of homologous chromosomes.
  3. Fertilisation of gametes to form zygote.
  4. Errors during DNA copying or mutations.

In asexually reproducing organisms only errors during DNA copying or mutations cause variations.
Since the extent of variations is much larger in sexually reproducing organisms, therefore, the chances of evolution is also much in sexually reproducing These variations enable the organisms to adapt themselves to the changing conditions and also help to face the struggle for Over the time, they and rise to new species.

Question 11.
How is the equal genetic contribution of male and female parents ensured in the progeny?
Answer:
Genetically organisms are of types

(i) Haploid : They have single set of chromosomes, where each chromosome is represented singly. As the chromosomes are the bearer of genes so haploids have single set of genes. A single gene determines the expression of character.
(ii) Diploid : ‘They have two sets Of homologous chromosomes, where the chromosome occur in pair, one maternal contributed by the mother through her ovum and the second Of the pair is contributed by the male parent through his sperm. The resultant cell zygote produces by the fusion of male and female gametes have two sets of chromosomes –  each set contributed’ by each parent. In diploids a character is controlled by two genes/factors. Both the father and mother contribute practically equal amount of genetic material to the child. It means that each trait can be influenced by both paternal and maternal DNA.

Question 12.
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement ? Why or why not ?
Answer:
No, many of the times the variations are not advantageous to an individual organism but still survive in a population, e.g., take the case of free ear lobe and attached ear lobe. Most of the other variations not only give survival advantage to an individual but also contribute to genetic drift. Thus, we can say that most of the variations lead to better adaptation of an organism to the changing environment. In this way, it gives survival advantage to that organism and will also survive in the coming population.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
An example of homologous organs is [NCERT]
(a) our arm and a dog’s foreleg
(b) our teeth and an elephant’s tusks
(c) potato and runners of grass
(d) All of the above
Answer:
(a) Our arm and a dog’s foreleg is the example of homologous organs.

Question 2.
The science, which deals with study of heredity and variations is called
(a) phylogeny
(b) embryology
(c) genetics
(d) palaeontology
Answer:
(c) The genetics is the study of heredity and variations and includes their occurrence, causes, benefits, disadvantages, significance, etc.

Question 3.
Archaeopteryx is a connecting link between
(a) reptiles and aquatic animals
(b) birds and insects
(c) reptiles and birds
(d) birds and dinosaurs
Answer:
(c) Archaeopteryx is a connecting link- between the reptiles and birds. It appears like a bird, but has other features which are present in reptiles, e.g. it has wings like bird, but teeth and tail like the reptilians.

Question 4.
For palaeontological studies a scientist will gather the evidences from
(a) study of homology
(b) study of analogy
(c) fossils
(d) All of these
Answer:
(d) Study of homologous and analogous organs indicates the origin and modification in organisms and study of fossils indicates the age and features of an organism.

Question 5.
In evolutionary terms, we have more in common with [NCERT]
(a) a Chinese school boy
(b) a chimpanzee
(c) a spider
(d) a bacterium
Answer:
(a) Chinese school boy because both of us belong to the same species, i.e. Homo sapiens.

Question 6.
Aditya was observing some organisms in lab and tried to compare them. The presence of which organs will confirm to him that they share evolutionary history?
(a) Analogous organs
(b) Paralogous organs
(c) Homologous organs
(d) None of these
Answer:
(c) Homologous organs are present in organisms who share evolutionary history. However, these organs perform different functions in different organisms.

Question 7.
New species may be formed if
I. DNA undergoes significant changes in germ cells. .
II. chromosome number changes in the gamete.
III. there is no change in the genetic material.
IV. mating does not take place.
(a) I and II
(b) I and III
(c) II, III and IV
(d) I, II and III
Answer:
(a) New species may be formed if the DNA changes are severe enough, such as a change in the number of chromosome. This leads to new variations.

Question 8.
Which of the following statements is not true with respect to variation?
(a) All variations in a species have equal chance of survival.
(b) Change in genetic composition results in variation.
(c) Selection of variants by environmental factors forms the basis of evolutionary processes.
(d) Variation is minimum in asexual reproduction.
Answer:
(a) All variations in a species do not have equal chances of survival. Some of the variations may be so drastic that the new DNA copy cannot work with the cellular apparatus it inherits. Such, a newborn cell dies soon.

Question 9.
Select the statement that describes characteristics of genes. .
(a) Genes are specific sequence of bases in a DNA molecule.
(b) A gene does not code for proteins.
(c) In individuals of a given species, a specific gene is located on a particular chromosome.
(d) Each chromosome has only one gene.
Answer:
(b) Genes are stretches of DNA found on chromosomes of a cell. A gene contains information for making proteins in a cell. A specific gene is located on a particular chromosome in individuals of a given species.

Question 10.
If a round, green seeded pea plant (RRyy) is crossed with wrinkled, yellow seeded pea plant (rrYY), the seeds produced in F1 – generation will be [NCERT Exemplar]
(a) round and yellow
(b) round and green
(c) wrinkled and green
(d) wrinkled and yellow
Answer:
(a) The cross between RRyy and rrYY seeds will produce RrYy (round and yellow) seeds in F1-generation, because round and yellow are the dominant traits.

Question 11.
From the list given below, select the character, which can be acquired but not inherited. [NCERT Exemplar]
(a) colour of eye
(b) colour of skin
(c) size of body
(d) nature of hair
Answer:
(c) Acquired traits develop in response to the environment. The size of the body is an acquired trait because it can vary based on the availability of less or more food. The other three colour of eye and skin and nature of hair are characters inherited from the parents.

Question 12.
According to the evolutionary theory, formation of a new species is generally due to [NCERT Exemplar]
(a) sudden creation by nature.
(b) accumulation of variations over several generations.
(c) clones formed during asexual reproduction.
(d) movement of individuals from one habitat to another
Answer:
(b) Accumulation of variations over several generations forms new species. Genetic drift accumulates different changes in sub-populations of a species. Also, natural selection may also operate differendy in the different geographic locations. Eventually, different groups of new species will be formed.

Question 13.
Select the incorrect statement. [NCERT Exemplar]
(a) Frequency of certain genes in a population changes over several generations resulting in evolution.
(b) Reduction in weight of the organism due to starvation is genetically controlled.
(c) Low weight parents can have heavy weight progeny.
(d) Traits which are not inherited over generations do not cause evolution.
Answer:
(b) The weight reduction due to starvation will not change the DNA of the germ cells, because low weight is not a trait that is genetically controlled or inherited. Also, low weight parents may have heavy weight progeny.

Question 14.
In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosome is/are
I. large chromosome
II. small chromosome
III. Y-chromosome IV X-chromosome
(a) I and II
(b) Only III
(c) III and IV
(d) II and IV
Answer:
(c) In human males, one pair called the sex chromosomes are unpaired. Here, one is a normal-sized X-chromosome while other is a short Y-chromosome. Women have a perfect pair of sex chromosomes, both called X.

Question 15.
Rajneesh was studying the fossils of two different types, fossil A was found in upper layer of Earth and B in deeper layers. What can be predicted regarding the age of these fossils?
(a) A has recently become extinct
(b) B has become extinct recently
(c) The time of extinction cannot be determined
(d) None of the above
Answer:
(a) Since, fossil A was found in upper layer of earth, it suggests that the organism has become extinct recently. Fossil B found in deeper layer must have become extinct long time ago and deposition of other layers occurred over it during this period.

Question 16.
A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic makeup of the tall parents can be depicted as [NCERT]
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
Answer:
(c) Parent with genotype TtWW produce two types of gametes TW and tW, while the other with genotype ttww produce only one type of gamete W.
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution MCQs Q16

NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution (Hindi Medium)

NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 1
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 2
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 3
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 4
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 5
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 6
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 7
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 8
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 9
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 10
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 11
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 12
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Hindi Medium 13

Class 10 Science Heredity and Evolution Mind Map

Accumulation Of Variation During Reproduction

  • Characters or features or traits are inherited from one generation to the next during reproduction.
  • This inheritance provides both a common basic body design & subtle changes in it for next generation.
  • When this generation reproduces, the offspring would have differences they inherit from previous generation as well as newly created differences.
  • Accumulation of these differences generation after generation leads to the development of variations in a population.
  • Different variations provide different advantages to the population and the variation which provide best survival advantages are inherited to the next generation.
  • For e.g. bacteria having variation to tolerate heat will survive and multiply better in heat wave.

Heredity
Heredity refers to the transmission of characteristics from parent to offspring by means of genes in the chromosomes.
Mendel’s Contributions

  • Mendel was the first scientist whose studies lead to the formulation of laws of inheritance.
  • He conducted cross hybridization experiments of garden pea plant (Pisum sativum) and studied the transmission of characters that had two contrasting traits such as round/wrinkled seeds, tall/short plants, white/’violet flowers etc.

Experiment 1: He cross pollinate pure breeds of tall (TT) & dwarf (tt) pea plant and calculated the percentages of tall & dwarf progeny.
Observation: F1 generation was tall (Tt) with no halfway characteristics.
F2 generation produced by self pollination of F1 included tall and short plants in 3:1. (Genotypic ratio 1:2:1 for TT:Tt:tt)
Inference: This indicates that both the tallness & shortness traits were inherited in the F, plants, but only the tallness trait was expressed.
Thus, two copies of the trait are inherited in each sexually reproducing organism. These two may be identical (TT or tt) or may be different (Tt), depending on the parentage.
Conclusion: This study leaded to the formulation of two laws:
Law of dominance: states that only one character expresses itself in F, generation.
Law of segregation: states that the two alleles of a character in an individual get separated or segregated during gamete formation and distributed randomly in gametes.

Experiment 2: He crossed the plant with two different characteristics such as tall plant with round seed and short plant with wrinkled seed. Other example may include round & green seeds (RRyy) and wrinkled & yellow seeds (rrYY).
Observation: F1 generation; all were tall & round i.e. tall & round are dominant.
F2 generation; tall plants with round seeds, tall with wrinkled seeds, short with round seeds, and short plants with wrinkled seeds in 9:3:3:1.
Similarly, round & yellow, round & green, wrinkled & yellow, and wrinkled & green in 9:3:3:1.
Inference: The tall/short trait and the round seed/wrinkled seed trait are independently inherited.
Conclusion: It formulated the law of independent assortment which states that genes of different characters located in different pairs of chromosomes are independent of one another in their segregation during gamete formation.

Sex Determination
Different species use different strategies for this:

  • Environment: for e.g. the temperature at which fertilised eggs are kept determines the sex of developing animals in the eggs. It is observed in animals like crocodile, turtle etc.
  • Snails can change sex. indicating that sex is not genetically determined.
  • Sex of an individual is genetically determined for e.g. humans.
    • Humans have 22 autosomal & 1 sex chromosome pairs. Females have XX & males have XY. Hence, sex of a child is determined by what he/she has inherited (X or Y) from the father since, child will always inherit X from the mother. If X is inherited from father then child will be a girl & if Y is inherited then a child will be a boy.
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Mind Map 1

Evolution

  • It refers to gradual change in the characteristics of the population (plants & animals) over successive generations.
  • Errors in DNA copying during reproduction, mutations, & natural selection account for the evolution.
  • Evolution gives rise to such a biodiversity at each level of biological organization such as at species level, among individuals, molecules etc.

Evolution And Classification
Classification is the process by which organisms are grouped into convenient categories based on some easily observable characters.

Characters such as cell type (prokaryote or eukaryote), single cell or multi cellular, presence or absence of nucleus, autotrophic (such as photosynthesis) or heterotrophic, sexual or asexual reproduction etc. are used to classify different organisms in different groups.

The more characteristics two species will have in common, the more closely they are related. And the more closely they are related, the more recently they will have had a common ancestor. For e.g. brother & sister are more closely related than a girl & her first cousin. Therefore, classification of species gives a reflection of their evolutionary relationship.

Tracing Evolutionary Relationships
Few evidences which help us to trace evolutionary
relationships among different organisms or species:

  • Comparative anatomy and morphology: study of similarities & differences among organisms to understand the common ancestry’.
    • Homologous: Similar structure different functions. It indicates common ancestry for e.g. bones of forelimbs in frog, lizard, bird & human.
    • Analogous: Similar functions but different structure. Different structures evolved for same function & hence having similarity. For e.g. wings of bats & birds, eye of octopus & mammals, etc.
  • Fossils: Remains of hard parts of life-forms found in rocks. They represent extinct organisms (e.g., Dinosaurs).
    • The age of the fossils can be estimated by two ways; relative depth of the fossils, dating fossils i.e. detection of ratios of different isotopes of the same element in the fossil material

Speciation

  • It refers to a gradual evolutionary process by which populations evolve to become different species.
  • Reproductive and geographical isolation play an important role in the process of speciation. They result in change in the frequency of an existing gene variant in a population i.e. genetic drift.
  • Over generations, genetic drift along with natural selection results in the formation of new’ species,
  • Other factors that may result in speciation are sudden severe DNA changes (mutation) such as change in chromosomal no., variation such as female green beetle will not mate with red males. Her behavior ensures the reproductive isolation between them and thus results in generation of new’ species.

Evolution Should Not Be Equated With ‘progress’

  • Evolution is simply the generation of diversity & shaping of diversity by environmental selection.
  • The only progressive trend in evolution seems to be the emergence of more and more complex body designs over time. However, that doesn’t mean that the older designs are inefficient.
  • For e.g. simplest life forms; bacteria inhabits the most inhospitable habitats like hot springs, deep-sea thermal vents & ice in Antarctica.

Human Evolution

  • Tolls, like excavating, time-dating and studying fossils, determining DNA sequences etc, have been used for studying human evolution.
  • All humans are a single species regardless of skin color or human races.
  • The earliest members of the human species, Homo sapiens, can be traced back to Africa i.e. we all come from Africa.
  • A couple of hundred thousand years ago, some of our ancestors left Africa while others stayed on.
  • The migrants slowly spread across the planet; from Africa to West Asia, then to Central Asia, Eurasia, South Asia, & East Asia.
  • They travelled down the islands of Indonesia and the Philippines to Australia, and they crossed the Bering land bridge to the Americas.

We hope this detailed article on NCERT Solutions For Class 10 Science Chapter 9 Heredity and Evolution is helpful. If you have any query regarding this article or  NCERT Solutions For Class 10 Science Chapter 9 Heredity and Evolution, leave your comments in the comment section below and we will get back to you as soon as possible.

NCERT Solutions for Class 10 Science Chapter 8 How Do Organisms Reproduce?

NCERT Solutions For Class 10 Science Chapter 8 How Do Organisms Reproduce?: In this article we will provide you detailed information regarding NCERT Solutions For Class 10 Science Chapter 8 How Do Organisms Reproduce?. Working on how do organisms reproduce class 10 NCERT Solutions will help candidates to score good marks in the subject Science. Further working on NCERT Solutions For Class 10 Science will help candidates to crack the Medicine competitive exams.

With the help of how do organisms reproduce class 10 important questions with answers students will score good marks in board exams as well. Read on to find out everything about NCERT Solutions For Class 10 Science Chapter 8 How Do Organisms Reproduce?.

Before getting into the details of how do organisms reproduce class 10 extra questions and answers, let’s have an overview of topics and subtopics under NCERT Solutions For Class 10 Science Chapter 8 How Do Organisms Reproduce?:

  1. How Do Organisms Reproduce?
  2. Do Organisms Create Exact Copies Of Themselves?
  3. Modes Of Reproduction Used By Single Organisms
  4. Sexual Reproduction

Free download NCERT Solutions for Class 10 Science Chapter 8 How Do Organisms Reproduce PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 8 Intext Questions

Page Number: 128

Question 1
What is the importance of DNA copying in reproduction?
Answer:
DNA copying has following importance in reproduction:

  • It maintains the characteristics of species.
  • It maintains the continuity of life.
  • From this, the characteristics and features of organisms are transformed to their progeny.
  • It produces variations in organisms which is the basis of evolution of new species.

Question 2
Why is variation beneficial to the species but not necessarily for the individual?
Answer:
The various populations of organisms interact with many types of ecological niches. This is important for them to survive in given conditions. In case of any damage caused to the ecological conditions of the population, the population gets adversely affected. The organisms which are able to survive, may reproduce to develop population which is adapted or suited to the varied conditions. Hence variation is beneficial to species, but not to the individuals.

Page Number: 133

Question 1
How is the process of pollination different from fertilisation ?
Answer:

Binary fissionMultiple fission
1. In this an organism divides into two similar organisms.1. In this an organism produces two or more organisms.
2. A cyst or thick layer is not formed around the cell.2. A cyst or thick layer is formed around the cell.
It generally occurs in favourable conditions
Example : Amoeba, paramecium
3. It can take place in unfavourable conditions too.
Example: Malarial parasite.

Question 2
How will an organism be benefited if it reproduces through spores ?
Answer:
An organism is benefited by reproducing through the spores because spores are surrounded by a thick layer which protects them in adverse conditions. When the favourable conditions occur, these spores start to grow again. In this way they are successfully live in unfavourable conditions.

Question 3
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration ?
Answer:
In complex multicellular organisms, specialised cells make up tissues, tissue make up organs, organs make up organ systems and finally organ systems make up organisms. Since complex multicellular organisms have a very high degree of organisation in their body, they cannot be reproduced from their cut body parts by the process of regeneration.

For example, a dog is a complex multicellular organism which cannot be regenerated from its cut body part say, a cut tail. This is because the cells present in the cut tail of a dog cannot produce dog’s organs like heart brain, lungs, stomach, intestines and limbs, etc, needed for the making of a complete dog.

Question 4
Why is vegetative propagation practised for growing some types of plants ?
Answer:
Vegetative propagation is practiced for growing such plants which usually do not produce seeds or produce non-viable seeds.

Question 5
Why is DNA copying an essential part of the process of reproduction ?
Answer:
DNA copying is essential part of the process of reproduction so that the characteristics of the parent organisms are transmitted to its offspring and at the same time some occasional variations are also produced in the offspring. The changes in the copy of DNA provide an organism the capability to survive in changing conditions.

Page Number: 140

Question 1
How is the process of pollination different from fertilisation ?
Answer:

PollinationFertilisation
1. The transfer of pollen grains from the anther of a stamen to the stigma of a carpel is called pollination.1. Fertilisation occurs when the male gamete present in pollen grain joins with the female gamete (or egg) present in ovule.
2. It takes place by various pollinating agents.2. It takes place by natural or artificial means.

Question 2
What is the role of the seminal vesicles and the prostate gland ?
Answer:
(i) Both seminal vesicle and prostate gland secretes fluids which forms a part of the semen. The fluid secreted from seminal vesicle forms 60% of semen while the fluid secreted from the prostate gland forms 30% of the semen. It makes the path smooth through which the sperms travel.
(ii) This fluid protects the sperms from the acids present in the urethra.
(iii) This fluid provides nutrition to sperms in the form of fructose, calcium and some enzymes.

Question 3
What are the changes seen in girls at the time of puberty ?
Answer:
The various changes occur in girls at puberty are :

  1. Hair grow under armpits and pubic region.
  2. Mammary glands (or breasts) develop and enlarge.
  3. The hips broaden.
  4. Extra fat is deposited in various parts of the body like hips and thighs.
  5. Fallopian tube, uterus and vagina enlarge.
  6. Ovaries start to release eggs.
  7. Menstruation (monthly periods) starts.
  8. Feelings and sexual drives associated with adulthood begin to develop.

Question 4
How does the embryo get nourishment inside the mother’s body ?
Answer:
In mother’s body, the embryo gets nutrition from the mother’s blood. For this, there is a special structure, called placenta. Placenta contains villi. There are empty spaces in mother’s tissues that cover the villi. It provides a large surface area for the transfer of glucose, oxygen and other substances from the mother to the embryo.

Question 5
A woman is using a copper-T. Will it help in protecting her from sexually transmitted diseases ?
Answer:
Copper-T is a contraceptive method which prevents implantation of the zygote inside the uterus. It cannot prevent a women from sexually transmitted diseases. These diseases are transmitted by contact which cannot be prevented by copper-T.

NCERT Solutions for Class 10 Science Chapter 8 Textbook Chapter End Questions

Question 1
Asexual reproduction takes place through budding in
(a) amoeba
(b) yeast
(c) plasmodium
(d) leishmania
Answer:
(b) Yeast

Question 2
Which of the following is not a part of the female reproductive system in human beings ?
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube
Answer:
(c) Vas deferens

Question 3
The anther contains
(a) sepals
(b) ovules
(c) carpel
(d) pollen grains
Answer:
(d) Pollen grains

Question 4
What are the advantages of sexual reproduction over asexual reproduction ?
Answer:
(i) In asexual reproduction, the offspring are almost identical to their parent because they have the same genes as their parent. So, much genetic variation is not possible in asexual reproduction. This is a disadvantage because it inhibits the further evolution of the organism.
(ii) In sexual reproduction the offspring, although similar to their parents, are not identical to them or to one another. This is because the offspring receive some genes from the mother and some from the father. Because of the mixing of genes of mother and father in various different combinations, all of the offspring have genetic variations. In this way, sexual reproduction leads to a greater variety in population. This means that a species (animal or plant) can adapt quickly to changes in its surroundings. This is because there are always likely to be some individuals which are more suited to the changes than others, and these individuals will survive and reproduce themselves.

Question 5
What are the functions performed by the testis in human beings ?
Answer:
The functions of testes in humans are following :
(i) After the stage of adolescent, testes produce male gametes in the human males which are called sperms.
(ii) A hormone called testosterone is produced in testes. Testosterone controls the development of reproductive organs and secondary sexual characters.

Question 6
Why does menstruation occur ?
Answer:
If the ovum (or egg) does not get fertilised (due to non-availability of sperm in the female body) then the thick and soft inner lining of uterus is no longer needed and hence it breaks. So, the thick and soft inner lining of uterus alongwith the blood vessels and the dead ovum (or egg) comes out of the vagina in the form of blood called menstruation. Menstruation occurs after the interval of every 28 days and the time period between ovulation and menstruation is about 14 days.

Question 7
Draw a labelled diagram of the longitudinal section of a flower.
Answer:
NCERT Solutions for Class 10 Science Chapter 8 How Do Organisms Reproduce Chapter End Questions Q8

Question 8
What are the different methods of contraception ?
Answer:
The different methods of contraception are as follow :
(i) Barrier method : In this method, condom, diaphragm and cervical caps are used. These prevent the entry of sperms in the female genital tract during sexual intercourse.
(ii) Chemical method : In this method a woman uses two kinds of pills (oral and vaginal pills). The oral pills are hormonal preparations which suppress the release of ovum in fallopian tube. These are called oral contraceptives. The vaginal pills/ creams are spermicidal. The chemicals in these spermicidals kill the sperms during their journey in the vaginal tract.
(iii) Intrauterine contraceptive devices : Intrauterine contraceptive devices such as copper-T are placed safely in the uterus by a skilled doctor. It prevents the sperms to reach the uterus.
(iv) Surgical method : In this method, a small part of vas deferens of male and fallopian tube of female is cut or tied by surgery. It is called vasectomy in males and tubectomy in females.

Question 9
How are the modes for reproduction different in unicellular and multicellular organisms ?
Answer:

Reproduction mode in unicellular organismsReproduction mode in multicellular organisms
(i) A sexual reproduction takes place in unicellular organisms.(i) Sexual reproduction takes place in multicellular organisms.
(ii) Only one organism is required in this method.(ii) A male and a female both are required in this method.
(iii) No special cells are present for reproduction.(iii) Special cells are present for reproduction.
(iv) No special organs are present for reproduction.(iv) Special organs are present for reproduction located at the fixed position in the body.

Question 10
How does reproduction help in providing stability to populations of species ?
Answer:
The introduction of variations during reproduction provides stability to the populations of various species by preventing them from getting wiped out during adverse conditions. Reproduction also helps to generate copies of individuals which are suited to a particular environment.

Question 11
What could be the reasons for adopting contraceptive methods ?
Answer:
The reasons for adopting contraceptive devices are as follow:

  1. To control the birth rate and prevent the increase in population.
  2. To reduce the adverse effects on mother’s body due to frequent pregnancy.
  3. To provide safety from sexually transmitted diseases.

NCERT Solutions for Class 10 Science Chapter 8 How Do Organisms Reproduce?

Reproduction: Reproduction in animals and plants (asexual) and (sexual) reproductive health – need and methods of family planning. Safe sex vs HIV/ AIDS. Child bearing and women’s health.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 8
Chapter NameHow Do Organisms Reproduce?
Number of Questions Solved26
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Page 128
Question 1.
What is the importance of DNA copying in reproduction?
Answer:
DNA copying in reproduction is important for maintenance of body designs and features. Moreover, DNA copying leads to variations. Variation is useful for the survival of species.

Question 2.
Why is variation beneficial to the species but not necessarily for the individual?
Answer:
Population of organisms reside in well-defined places or niches in the ecosystem. However, niches can change because of reasons beyond the control of the organisms, e.g., temperature changes, water level changes, etc. If population of reproducing organisms suited to particular niche and if the niche is drastically altered, the population can be wiped out. However, if some variations are present in a few inAividuals in these populations, there will be chances for their survival. The surviving individual can further reproduce and develop a population according to the changed niche, Thus, variation is beneficial to the species but not necessarily for the individual.

More Resources for CBSE Class 10

Page 133:

Question 1.
How does binary fission differ from multiple fission ?
Answer:
When two new daughter cells are formed as a result of fission. It is called binary fission, e.g., Amoeba.When many daughter cells are formed as a result of fission, this is called multiple fission, e.g., Malarial parasite.

Question 2.
How will an organism be benefited if it reproduces through spores?
Answer:
Spore formation is an asexual mode of reproduction. Spores formed are covered by
thick walls that protect them from adverse conditions. During favourable condition thick resistant wall breaks down and new organism grows from it.
Spores are very light weight and they easily get dispersed through winds which give them more variations and thus better chances of survival.

Download NCERT Solutions for Class 10 Science Chapter 8 How Do Organisms Reproduce PDF

Question 3.
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Answer:
Complex organisms are not simply a random collection of cells where sPecialized cells are organised as tissues, and tissues ale organised into organs which then have to be placed at definite positions in the body. In such a carefully organised situation, it is not easy to develoP organism through regeneration

Question 4.
Why is vegetative propagation practised for growing some type of plants?
Answer:
Vegetative propagation makes possible for the propagation of plants such as banana, orange, rose and jasmine that have lo6t the capacity to Produce seeds. Moreover, all plants produced through vegetative propagation are genetically similar to the parent plant.

Question 5.
Why is DNA copying an essential part of the process of reproduction?
Answer:
The process of reproduction results in the production of off springs which resemble to their parents. This means during the reproduction there must be a transfer of the blueprint of the body design from parent to the off springs. As we know DNA contains all the information that passes from parents to the next generation, so before reproduction, DNA is copied in the parent cell. Out of these two copies, one copy is passed to the newly formed individual.

Page 140

Question 1.
How is the process Of pollination different from fertilization ?
Answer:
Pollination is the transfer of pollen grains from the anther to the stigma Of a flower whereas fertilization is the fusion Of male gamete with female gamete (egg).

Question 2.
What is the role of the seminal vesicles and the prostate gland ?
Answer:
Seminal vesicles and the prostate gland add their secretions so that the sperms are in a fluid (semen) which makes their transport easier and this fluid also provides nutrition.

Question 3.
What are the changes seen in girls at the time Of puberty ?
Answer:
Changes seen in girls at the time of puberty are :
1. Breast size begins to increase.
2. Girls begin to menstruate.
3.Growth Of pubic hair.
4.Skin becomes oily.

Question 4.
How does the embryo get nourishment inside the Mother’s body?
Answer:
embryo gets nutrition from mother’s blood with the help Of a special tissue called placenta. Through placenta, glucose and oxygen pass from mother to the embryo. Moreover, waste substance of embryo are removed through placenta into the
mother’s blood.

Question 5.
If a woman is using a copper-T will it help in protecting her from sexually transmitted diseases?
Answer:
No, copper-Twill not protect her from Only Barrier methods protect from sexually transmitted diseases.

Page 141

Question 1.
Asexual reproduction takes place through budding in :
(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania.
Answer:
(b) Yeast.

Question 2.
Which of the following is not a pan Of the female reproductive system in human beings ?
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube
Answer:
(c) Vas deferens.

Question 3.
The anther contains :
(a) Sepals
(b) Ovules
(c) Carpel
(d) Pollen grains.
Answer:
(d) Pollen grains

Question 4.
What are the advantages of sexual reproduction over asexual reproduction?
Answer:
Sexual reproduction leads to new combination Of genes as it involves two parents and meiosis. This produces variation in offspring. Variations are the basis for evolution.

Question 5.
What are the functions performed by the testes in human beings?
Answer:
Functions Of testes are .
(i) Testes produce sperms.
(ii) Testosterone (male sex hormone) is also produced by testes.

Question 6.
Why does menstruation occur?
Answer:
If the egg is not fertilized and uterus does not get zygote, the developed lining slowly breaks and menstruation occur.

Question 7.
What are the different methods of contraception?
Answer:
There are three main methods of contraception :

  1. Barrier methods,
  2. Chemical methods, and
  3. Surgical methods.

1. Barrier methods: In barrier methods, physical devices such as condom, diaphragm and cervical caps are used. They prevent the entry Of sperms in the female genital tract during copulation.
2. Chemical methods: The chemical methods make use of specific drugs by females. There are two types of such drugs, Oral pills and vaginal pills. Oral pills are mainly hormonal preparation, and are called oral contraceptives (OCS).
3. Surgical methods: In the surgical methods, a small portion of vas deferens in male, and the fallopian tube in female, in surgically removed or ligated (tied). It is called vasectomy in males and tubectomy in females.

Apart from these three methods the intrauterine contraceptive devices are used to prevent pregnancies. The use of Intra Uterine Contraceptive Devices (IUCDs) is also very effective and popular. A copper-T is placed safely inside the uterus by a practising doctor or a skilled nurse. IUCDs prevent implantation in the uterus.

Question 8.
How are the modes for reproduction different in unicellular and multicellular organisms ?
Answer:
Unicellular organisms reproduce asexually whereas multicellular organisms reproduce manly by n 1 reproduction.

Question 9.
How does reproduction help in providing stability to populations Of species?
Answer:
The rate Of birth and death in a given population determine its stability. The rate of birth should be approximately equal to the rate of death. So, by checking birth rate, which is increasing at an alarming rate, stability to population of species can be provided

Question 10.
What could be the reasons for adopting contraceptive methods?
Answer:
Frequent pregnancies have an adverse effect on the health of a woman. Frequent and unwanted pregnancies can be avoided by adopting contraceptive methods. Also, these methods check population growth by controlling child birth rate.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
Asexual reproduction takes place through budding in [NCERT]
(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania
Answer:
(b) Asexual reproduction in Hydra and yeast takes place by budding.

Question 2.
The ability of a cell to divide into several cells during reproduction in Plasmodium is called [NCERT Exemplar]
(a) budding
(b) reduction division
(c) binary fission
(d) multiple fission
Answer:
(d) Multiple fission Organisms divide into many daughter cells simultaneously, e.g. Plasmodium.

Question 3.
The anther contains [NCERT]
(a) sepals
(b) ovules
(c) carpels
(d) pollen grains
Answer:
(d) Anther is the male reproductive part in plants. It contains pollen grains, having male germ cells.

Question 4.
Characters that are transmitted from parents to offspring during reproduction show [NCERT Exemplar]
(a) only similarities with parents
(b) only variations with parents
(c) both similarities and variations with parents
(d) neither similarities nor variations
Answer:
(c) In sexual reproduction, the offsprings are not exactly identical to the parents or to one another. This is because the offsprings receive some genes from mother and some from father. Because of mixing of genes on re-establishment of the exact number of chromosomes as in the parents, the offsprings show both similarities and variations with their parents.

Question 5.
Which among the following diseases is not sexually transmitted? [NCERT Exemplar]
(a) Syphilis
b) Hepatitis
(c) HIV-AIDS
(d) Gonorrhoea
Answer:
(b) The diseases, which are spread by sexual contact with an infected person are called Sexually Transmitted Diseases or STDs, e.g. gonorrhoea, syphilis and AIDS. Hepatitis is a water borne viral disease which affects liver.

Question 6.
Which of the following is not a part of the female reproductive system in human beings? [NCERT]
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube
Answer:
(c) Vas deferens is a part of male reproductive system in humans.

Question 7.
A feature of reproduction that is common to Amoeba, Spirogyra and yeast is that [NCERT Exemplar]
(a) they reproduce asexualiy
(b) they are all unicellular
(c) they reproduce only sexually
(d) they are all multicellular
Answer:
(a) Amoeba and yeast are unicellular while Spirogyra is multicellular. But, all the three reproduce asexualiy.

Question 8.
Which among the following statements are true for unisexual flowers? [NCERT Exemplar]
I. They possess both stamen and pistil.
II. They possess either stamen or pistil.
III. They exhibit cross-pollination.
IV. Unisexual flowers possessing only stamens cannot produce fruits.
(a) I and IV
(b) II, III and IV
(c) III and IV
(d) I, III and IV
Answer:
(b) The flowers which are unisexual (papaya, watermelon) contain either stamens or carpels. Since, only one reproductive organ is present in them, they depend on cross-pollination to form zygote after fertilisation. Both stamens and carpels are required for fertilisation, so only one of them cannot produce fruits.

Question 9.
Length of pollen tube depends on the distance between [NCERT Exemplar]
(a) pollen grain and upper surface of stigma.
(b) pollen grain on upper surface of stigma and ovule.
(c) pollen grain in anther and upper surface of stigma.
(d) upper surface of stigma and lower part of style.
Answer:
(b) Length of pollen tube depends on the distance between pollen grain on upper surface of stigma and ovule. A pollen grain falls on the stigma of the carpel, bursts open and develops a pollen tube downwards through the style towards the ovule in the ovary.

Question 10.
Which among the following statements arer true for sexual reproduction in flowering plants? [NCERT Exemplar]
I. It requires two types of gametes.
II. Fertilisation is a compulsory event.
III. It always results in formation of zygote.
IV. Offsprings formed are clones.
(a) I and IV
(b) I and II
(c) I, II and III
(d) I, II and IV
Answer:
(c) Sexual reproduction creates variation in organisms, so, clones cannot be produced through it. Clones are identical copy of parent organism. Sexual reproduction needs two type of gametes, i.e. male and female to form zygote after fertilisation.

Question 11.
Factors responsible for the rapid spread of bread mould on slices of bread are [NCERT Exemplar]
I. large number of spores.
II. availability of moisture and nutrients in bread.
III. presence of tubular branched hyphae.
IV formation of round-shaped sporangia
(a) I and III
(b) II and IV
(c) I and II
(d) III and IV
Answer:
(c) Under favourable Conditions (like damp and warm conditions, availability of nutrients), the fungal spores present in the air, lands on food, germinate and produce new plaints.

Question 12.
During adolescence various changes occur in the body of humans. Mark one change associated with sexual maturation in males. [NCERT Exemplar]
(a) Loss of milk teeth
(b) Increase in body height
(c) Cracking of voice
(d) Weight gain
Answer:
(c) Hypertrophy of larynx results in low pitched. cracking voice in human males during adolescence.

Question 13.
Observe the diagram given along side.
NCERT Solutions for Class 10 Science Chapter 8 How Do Organisms Reproduce MCQs Q13
What happens after the above stage?
(a) The ovary splits open
(b) Ovary develops into a fruit and ovules into seeds
(c) The pvules are dispersed
(d) Germination of seeds takes place
Answer:
(b) Ovary develops into a fruit and ovulesdnto seeds as in the above given diagram fertilisation has already taken place.

Question 14.
What in your opinion could be the best reason to explain why menstruation is not taking place in a healthy woman?
(a) Early release of ovum
(b) Psychological reason
(c) Fertilisation of ovum
(d) Build up of female sex hormones in the blood stream
Answer:
(c) If a woman is not having her menstruation on time the probable reason from the given option is that fertilisation of ovum has taken place. Because, during gestation period of pregnancy, menstruation does not take place.

Question 15.
The correct sequence of reproductive stages seen in flowering plants is [NCERT Exemplar]
(a) gametes, zygote, embryo, seedling
(b) zygote, gametes, embryo, seedling
(c) seedling, embryo, zygote, gametes
(d) gametes, embryo, zygote, seedling
Answer:
(a) Correct sequence of reproductive stages in flowering plants is → formation of gametes → fusion of gametes to form zygote → zygote develops into embryo in the ovary → ovule develops a tough coat and converts into a seed.

Question 16.
Offsprings formed by asexual method of reproduction have greater similarity among themselves because [NCERT Exemplar]
I. asexual reproduction involves only one parent.
II. asexual reproduction does not involve gametes.
III. asexual reproduction occurs before sexual reproduction.
IV. asexual reproduction occurs after sexual reproduction.
(a) I and II
(b) I and III
(c) II and IV
(d) III and IV
Answer:
(a) Offsprings have greater similarity as only one parent is involved in asexual reproduction thus, no gametes are formed.

Question 17.
Two flowers are identified by a botanist with the following features that flower A is having only stamen and flower B is having both stamen and pistil. Which of the following statements is correct?
(a) Flower A will bear seeds and flower B cannot bear seeds after fertilisation.
(b) Flower A will produce pollen grains and flower B cannot produce pollen grains.
(c) Flower A cannot be fertilised and flower B can show fertilisation.
(d) Neither flower A and nor flower B can show self-pollination.
Answer:
Option (c) is correct. Since, flower A bears only stamen, i.e. male reproductive part so, it cannot get fertilised. And flower B bears both male and female reproductive parts, therefore it can get fertilised by pollination and can change into fruit.

NCERT Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce (Hindi Medium)

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Class 10 Science How Do Organisms Reproduce Mind Map

  • Reproduction is a biological process in which an organism gives rise to young ones similar to themselves.
  • Basic event in reproduction is the creation of a DN A copy.
  • Cells use chemical reactions to build two copies of the DNA in a reproducing cell.
  • In addition, DNA copying is accompanied by the creation of an additional cellular apparatus.
  • Then each DNA copy is separated with its own cellular apparatus.
  • Effectively, a cell divides to give rise to two cells.

Asexual Reproduction

When offspring is produced by single parent with or without the involvement of gamete formation.

Fragmentation

  • Parent organism breaks into smaller fragments upon maturation, each fragment grows into a new individual.
  • It is shown by multi-cellular organisms with simple body organization for e.g. Spirogyra

Fission

  • Organisms divide mitotically into two halves, each behaves like independent individual. It is termed as binary fission and is mostly shown by bacteria and protozoa.
  • Binary fission can take place in any plane as observed in Amoeba, or it can occur in a definite orientation for e.g. Leishmania (causes kala-azar), Euglena (longitudinal), Paramecium (transverse) etc.
  • In few organisms parent cell divides into many daughter cells simultaneously which is termed as multiple fission. It is observed in Plasmodium.

Budding

  • Formation of daughter organism takes place from a small projection called as bud. For e.g. Hydra, Yeast etc
  • Organisms such as Hydra use regenerative cells for reproduction in the process of budding.
  • Repeated cell division at one specific site leads to the formation of an outgrowth called as bud.
  • These buds develop into tiny individuals and detach form parent body once they become fully mature.
  • Detached organism acts as an independent organism.

Regeneration

  • It is an ability of simple organisms to re-grow their lost body parts.
  • In asexual reproduction, this ability is used by many organisms to give rise to new individual from their body parts. That is, if the individual is somehow’ cut or broken up into many pieces, many of these pieces grow into separate individuals.
  • For e.g. Hydra and Planaria
  • It is carried out by specialized cells which proliferate & differentiate to make various cell types tissues.
  • These changes take place in an organized sequence referred to as development.
  • However, regeneration is not the same as reproduction, since most organisms would not normally depend on being cut up to be able to reproduce.

Spore Formation

  • An individual divides into no. of small spores, each spore giving rise to new individual.
  • Spores are covered by thick walls that protect them until they come into contact with moist surface or suitable environment and can begin to grow. E.g. Spore formation in Rhizopus

Vegetative Propagation

  • It refers to the formation of new plants from parts of parent plants such as root, stem, leave etc. These parts are termed as vegetative units or vegetative propagules. For e.g. buds produced in the notches along the leaf margin of Bryophyllum fall on the soil and develop into new plants
  • Advantages of vegetative propagation:
    • Vegetative propagation is used in methods such as layering, cutting, grafting to grow many plants like sugarcane, roses, or grapes for agricultural purposes.
    • Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.
    • It makes it possible to propagate plants that have lost the capacity to produce seeds such as banana, orange, rose and jasmine.
    • Plants produced are genetically similar enough to the parent plant to have all its characteristics.

Sexual Reproduction

It involves the formation and fusion of the gametes. It leads to formation of variations in individuals. Variations form the basis of evolution of the species and ensure the survival of the species.
Reproduction in Human Beings
Puberty: The period during which adolescents reach sexual maturity and become capable of reproduction.

  • Changes in girls during puberty: breast size begins to increase, darkening of skin of nipples, & girls begin to menstruate.
  • Changes in boy during puberty: hair growth on face, voices begin to crack & occasional erection & enlargement of penis
  • Changes common to both boys & girls: hair growth in various parts such as armpits, genital area, thin hairs on arms & legs and skin may become oily.

Female Reproductive System

  • It consists of a pair of ovaries, pair of oviduct (fallopian tube), uterus, cervix, & vagina.
  • One egg is produced every month by one of the ovaries after reaching the age of puberty. The egg is carried from the ovary to the womb through a thin oviduct or fallopian tube.
  • Uterus serves as womb and is richly supplied with blood vessels to nurture the developing embryo.
  • Vagina serves as the site of entry of sperm during sexual intercourse.

Male Reproductive System

  • It consists of a pair of testes located outside the body in a pouch called scrotum. It helps in maintaining lower temperature which favors the perm formation. Testes are responsible for synthesizing sperms and testosterone.
  • Sperms are tiny bodies consists of mainly genetic material and a tail that helps them to move towards the female germ-cell.
  • Sperms are then delivered through vas deferens which unites with urethra to form a common passage for sperm and urine.
  • Accessory glands like seminal vesicles, prostate, and bulbourethral add their secretion to sperm. It makes the sperm fluid in nature that not only eases the transportation of sperm but also provide the nutrition to it.

Reproductive Health

  • Sexually transmitted diseases include bacterial infections (gonorrhea, syphilis etc) & viral infections (warts, AIDS etc).
  • Contraception refers to the act of preventing the unwanted pregnancies. Contraceptive methods may fall in following categories:
    • Mechanical barrier: e.g. condom, diaphragms. They also prevent STDs.
    • Oral contraceptives: they change hormonal balance, inhibits ovulation & thus fertilization e.g. saheli, iPill, etc.
    • Intra uterine device: plastic or metal devices placed in the uterus for e.g. loop, copper-T etc.
    • Surgical methods such as vasectomy & tubectomey.

Events of Reproduction

  • The sperms after entering the vaginal passage travel upwards and reach the oviduct where they may fertilize the egg.
  • Post-fertilization, the zygote gets implanted in the lining of the uterus, and starts dividing.
  • Special tissue called placenta is developed to provide nutrition to the developing embryo as well as for removing waste from it.
  • The development of a child takes up approx, nine months.
  • The child is born as a result of rhythmic contractions of the muscles in the uterus.

Menstruation
Menstrual cycle is a cyclic event that places roughly every month in females after puberty. Unfertilized egg lives for 1 day after which it degenerates. Consequently, uterus lining slowly breaks & comes out through the vagina as blood & mucus. This discharge is known as menstruation which lasts for about 2-8 days.

Sexual Reproduction in Flowering Plants
Stamens and carpels are the reproductive parts of a flower which contain the germ-cells. Stamen is the male reproductive part and it produces pollen grains. Carpel is the female reproductive part made up of three parts: ovary, style and stigma.
The ovary contains ovules and each ovule has an egg cell.
The flower may be unisexual i.e. contains either stamens or carpels e.g. papaya, watermelon or bisexual i.e. contains both stamens and carpels e.g. Hibiscus, mustard.
Transfer of pollen grains (shed from the anther) to the stigma of a pistil is termed pollination. Two types: self-pollination and cross pollination. Pollinating agents are air, water, insects, & animals.
Compatible pollen grain germinates on stigma to produce pollen tube. Pollen tube grows through tissues of stigma, style & reaches ovary.
Fertilization results in the formation of zygote which develops into an embryo.
The ovule develops a tough coat and is gradually converted into a seed. The ovary grows rapidly and ripens to form a fruit.
The petals, sepals, stamens, style and stigma may shrivel and fall off.
The seed develops into a seedling under appropriate conditions which is known as germination.

We hope this detailed article on NCERT Solutions For Class 10 Science Chapter 8 How Do Organisms Reproduce? helps you. If you have any query regarding the how do organisms reproduce class 10 notes NCERT solutions, drop it in the comment section below and we will get back to you.

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

NCERT Solutions For Class 10 Science Chapter 7 Control And Coordination: In this article, you will find out everything about NCERT Solutions For Class 10 Science Chapter 7 Control And Coordination. Candidates can find everything about control and coordination class 10 extra questions with answers in this article.

The answer to each and every question in class 10 science chapter 7 notes is provided along with complete, step-wise solutions for candidates better understanding. This will further help candidates in their home assignments and as well as practice sessions. Read on to find everything about Control and Coordination Class 10.

Free download NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 7 Control And Coordination, let’s have an overview of topics and subtopics under control and coordination class 10 NCERT questions:

  1. Control And Coordination
  2. Animals – Nervous System
  3. Coordination In Plants
  4. Hormones In Animals

Control and Coordination Class 10

NCERT Solutions for Class 10 Science Chapter 7 Intext Questions

Page Number: 119

Question 1
What is the difference between a reflex action and walking?
Answer:

Reflex actionWalking
1. It is the action which is performed automatically.1. It is a response to the information transmitted by nerve to muscles of the legs. In this case, thinking is involved.
2. It is controlled and coordinated by spinal cord.2. Brain instructs and controls leg muscles to move.
3. It is an involuntary action.3. It is a voluntary action.

Question 2
What happens at the synapse between two neurons?
Answer:
The small empty space between two nerve cells is called synapse. At synapse, a chemical substance is produced at the end of axon of one nerve cell that reaches to the other nerve cell through the dendrite. Thus, information is transmitted from one nerve cell to other nerve cell by synapse.

Question 3
Which part of the brain maintains posture and equilibrium of the body ?
Answer:
Posture and equilibrium of the body are controlled by cerebellum.

Question 4
How do we detect the smell of an agarbatti (incense stick) ?
Answer:
The smell of agarbatti (incense stick) diffuses in the air. It is detected by olfactory receptors present in the nose. This information is sent to olfactory lobe by sensory nerves located in the forebrain. It responds to the information.

Question 5
What is the role of the brain in reflex action ?
Answer:
There is no role of brain in reflex action. These involuntary actions are controlled by the spinal cord which take place immediately without thinking of how to respond to the stimuli.

Page Number: 122

Question 1
What are plant hormones ?
Answer:
Plant hormones are also called phytohormones. Plant hormones are the chemical substances which help in controlling growth, flowering, height, development of plants and their response to the environment.

Different types of phytohormones are – auxins, gibberllins, cytokinins, abscisic acid and ethylene.

Question 2
How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light ?
Answer:

Movement of leaves of sensitive plantMovement of a shoot towards light
1. It is a nastic movement which does not depend on the direction of stimulus applied.1. It is a tropic movement which depends on the direction of stimulus applied.
2. The stimulus is touch.2. The stimulus is light.
3. It is caused by the sudden loss of water from the swellings at the base of leaves.3. It is caused by the unequal growth on the two sides of the shoot.
4. It is not a growth movement.4. It is a growth movement.

Question 3

Give an example of a plant hormone that promotes growth.
Answer:
Auxin.

Question 4
How do auxins promote the growth of a tendril around a support ?
Answer:
When the tip of a tendril touches a support, then the auxins present in its tip move to that side of tip which is away from the support. Auxins promote growth. So, due to more auxins in it, the side of tendril away from the support grows faster (and becomes longer) than the side which is in contact with the support and makes the tendril twirl (or bend) around the support.

Question 5
Design an experiment to demonstrate hydrotropism.
Answer:
Take two glass troughs A and B and fill each one of them two-thirds with soil. In trough A plant a tiny seedling. In trough B plant a similar seedling and place a c/ay pot inside the soil. Water the soil in trough A daily and uniformly. Do not water the soil in trough B but put some water in the clay pot. Leave both the troughs for a few days.
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination Intext Questions Page 122 Q5
Now, dig up the seedlings carefully from both the troughs without damaging their roots. We will find that the root of seedling in trough A is straight. On the other hand, the root of seedling in trough B is found to be bent to the right side i.e., towards the clay pot containing water.
In trough A, the root of the seedling gets water from both sides. But in trough B, the roots get water oozing out from the clay pot which is kept on the right side. Therefore, the root of seedling in trough B grows and bends towards the source of water to the right side. This experiment shows that the root of a plant grows towards water. In other words, the root of a plant is hydrotropism.

Page Number: 125

Question 1
How does chemical coordination take place in animals ?
Answer:
Chemical coordination in animals takes place through the hormones secreted by the endocrine glands. Coordination in animals takes place through hormone system as well as nervous system which is called endocrine system. Endocrine glands secrete animal hormones directly into the blood that reach to the specific cells. Special type of molecules are present on the surface of cells to detect these hormones. These cells act according to the information that a particular hormone carries.

Question 2
Why is the use of iodised salt advisable ?
Answer:
It is advised to use iodised salt because thyroid gland needs iodine to produce thyroxin hormone. Thyroxin hormone controls all the metabolic activities of our body like metabolism of carbohydrates, fats and protein etc. Due to the deficiency of thyroxin a disease called goitre is caused.

Question 3
How does our body respond when adrenaline is secreted into the blood ?
Answer:
The heart beat increases when adrenaline is secreted into the blood so that more oxygen is supplied to our muscles. The blood supply to the digestive system and skin decreases because the small arteries around the muscles of these organs contract. This turns the direction of blood towards our skeletal muscles. The breathing rate also increases due to the contractions of the diaphragm and rib muscles. All these responses enable us to face the situations of fear and anger.

Question 4
Why are some patients of diabetes treated by giving injections of insulin ?
Answer:
Insulin hormone regulates blood sugar levels. If this is not secreted in proper amounts, the sugar level in the blood rises. This causes many harmful effects.
To treat harmful effects of increased level of blood sugar, the diabetic patients are treated by giving injections of insulin.

NCERT Solutions for Class 10 Science Chapter 7 Textbook Chapter End Questions

Question 1
Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Answer:
(d) Cytokinin

Question 2
The gap between two neurons is called a
(a) dendrite
(b) synapse
(c) axon
(d) impulse
Answer:
(b) Synapse

Question 3
The brain is responsible for
(a) thinking
(b) regulating the heart beat
(c) balancing the body
(d) all of the above
Answer:
(b) All of the above

Question 4
What is the function of receptors in our body ? Think of situations where receptors do not work properly. What problems are likely to arise ? [AICBSE 2016]
Answer:
Receptors are specialised cells located in our sense organs like ear, nose, skin, tongue and eyes. The function of receptors is to detect information from the environment. For example, olfactory receptors detect smell. If receptors do not work properly, the information obtained from the environment will be delayed to reach the spinal cord or brain. In this situation, the response to the environmental stimulus will be delayed causing harm to the body. For example, if skin receptors are damaged, and one accidentally touches a hot object, then his/her hands might get burn as the damaged receptor cannot perceive the external stimuli of heat and pain.

Question 5
Draw the structure of a neuron and explain its function. [AICBSE 2017]
Answer:
Nerve cell or neuron is the functional unit of nervous system. A nerve cell has three parts-
(i) cell body
(ii) dendrite
(iii) axon
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination Chapter End Questions Q5
Function : The function of nerve cells is to carry information in the form of electrical signals which are called nerve impulses. Cells receive stimulus to send it to spinal cord and brain and carry the message from brain to the target organ.

Question 6
How does phototropism occur in plants ?
Answer:
The movement in any part of a plant due to light is called phototropism. The shoot of plant shows positive phototropism and roots show negative phototropism.
Phototropism in plants occurs due to the hormone auxin. When light falls on one side of a plant, the secretion of auxin hormone is more in the part away from the light. Hence, auxin causes growth in length of the cells in shady part. So, the plant appears to bend towards light.

Question 7
Which signals will get disrupted in case of a spinal cord injury ?
Answer:
(i) All the involuntary actions will get disturbed.
(ii) Reflex actions will be disturbed because reflexes are located in the spinal cord. Therefore, the quick responses required to safe guard the body will not take place.

Question 8
How does chemical coordination occur in plants ?
Answer:
Chemical coordination in plants takes place with the help of plant hormones. In most of the regions where division takes place (meristematic regions) stimuli cells secrete chemical compounds (hormone). These substances identify the information by stimulating the other nearby cells and communicating the information.

Question 9
What is the need for a system of control and coordination in an organism ?
Answer:
An organism needs control and coordination system for the following functions :
(i) To save the body of the organisms from the harmful changes in the environment.
(ii) To control the speed of voluntary and involuntary actions.
(iii) To have the capability to think and learn for responding to any stimuli.

Question 10
How are involuntary actions and reflex actions different from each other ?
Answer:

Involuntary actionsReflex actions
 1. Those actions which occur immediately without any thinking are called involuntary actions.1. Reflex action is an immediate response to an event which does not require any processing by brain.
2. Involuntary actions are controlled by mid and hind brain.
Example: Breathing, beating of heart, etc.
2. Reflex actions are controlled by spinal cord.
Example: Sneezing, coughing, etc.

Question 11
Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Answer:

Nervous mechanismHormonal mechanism
It is a fast process.It is a slow process.
Arteries and glands are affected.It affects the target organ.
It transmits in electrochemical form.It transmits in chemical form.
It does not control metabolism.It controls metabolism.
Growth is not affected.Growth is affected.

Question 12
What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs ?
Answer:

Movement in a sensitive (mimosa) plantMovement in legs of a human
1. The leaves of a sensitive plant like mimosa are sensitive to touch.1. Leg is in control of nerve muscles.
2. It is not controlled by any part of the plant.2. It is controlled by brain and spinal cord.
3. In this, cells change their shape on changing the amount of water in them.3. Amount of water has no effect on the movement of muscles.
changing the amount of water in them.the movement of muscles.
4. The movement in a sensitive plant are nastic movement.4. The movement in our leg is due to voluntary nervous system.

Control and Coordination Class 10 HOTS

Question 1.
What type of plant movement is seen in the diagram of coiling of tendril?
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination HOTS Q1

                                                                  Or

How do auxins promote the growth of a tendril around a support? Describe in brief. (CCE 2012)
Answer:
Thigmotropism or curvature movement that occurs in response to contact. Less auxin is present in the region of contact. The free side having more auxin shows more growth. This causes the tendril to coil over the support.

Question 2.
Identify and label the parts shown as A and B in the accompanying figure.
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination HOTS Q2
Answer:
Dorsal view of thyroid an parathyroid.
A – Thyroid,
B- Parathyroid.

Question 3.
What are the hormones involved in providing milk to the suckling infant ?
Answer:
1. Prolactin (Maternity Hormone). Production of milk.
2. Oxytocin Ejection of milk.

Question 4.
How does pancreas control glucose level of blood ?
Answer:
Pancreas produces two hormones

  1. Insulin from P-cells of islet of Langerhans and
  2. Glucagon from a- cells of islets of langerhans.

Insulin is produced when glucose level of blood rises. Insulin helps the cells to withdraw glucose from blood. It also converts glucose into glycogen in liver and muscles.

Question 5.
Glucagon is secreted when glucose level of blood falls. It mobilises reserve food like glycogen into glucose. What is pregnancy hormone ? Why is it known so ?
Answer:
Progesterone is called pregnancy hormone. It helps in maintaining pregnancy by non-formation of new ova, promoting thickening and secretory activity of uterine wall and attachment of embryo to the uterine wall.

Question 6.
What is dormin ?
Answer:
Dormin is the other name of plant hormone abscisic acid. The hormne induces dormancy in buds and seeds. So it has been called dormin.

Question 7.
(a)

  1. Name the parts labelled A and B in the neuron drawn above.
  2. Which part acquires the information in the neuron ?
    NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination HOTS Q7
  3. Through which part does the information travel ?
  4. In what form does this information travel ?
  5. Where is the impulse converted into a chemical signal for onward transmission ?

(b) Name the hormone secreted by thyroid. What is the function ?
(c) Why is the use of iodised salt advisable ?
(CBSE A.I. 2008 Compt.)
Answer:
(a)

  1. A-Dendrite, B-Axon
  2. Dandrite.
  3. Dandrite to cell body or cyton to axon.
  4. Electrical impulse
  5. In the region of synapse.

Impulse stimulates the release of chemical neurotransmitter from the surface of presynaptic knob or bouton of axon terminal. Neurotransmitter (e.g. acetylcholine) comes in contact with chemoreceptor sites of post-synaptic membrane of the next neuron and generates a fresh impulse.

(b) Thyroxine:
Function of Thyroxine. It controls

  1. Basal metabolic rate
  2. Metabalism of carbohydrates, fats and proteins
  3. Consumption of energy in physical activity and body temperature
  4. Development and differentiation.

(c) Iodised Salt: Salt is iodised to provide iodine to thyroid for synthesis of thyroxine which is iodine containing hormone.

Question 8.
(a) What are plant hormones ? Give one example each of a plant hormone that

  1. promotes growth
  2. inhibits growth.
  3. promotes cell division
  4. promotes the growth of a tendril around a support. (CCE 2011)

(b) Name the parts labelled A, B and C in the diagram given below. Write one function of each part. (CBSE A.I. 2008 Comptt. Delhi 2008 Comptt.)
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination HOTS Q8
Answer:
(a) Plant Hormones:
Phytohormones are chemical substances other than nutrients produced naturally in plants which regulate growth, development, differentiation and a number of physiological processes, e.g., auxin, gibberellins, abscisic acid, cytokinins.

  1. Hormone That Promotes Growth. Auxin/Gibberellin.
  2. Hormone That Inhibits Growth. Abscisic acid or ABA
  3. Hormone That Promotes Cell Division. Cytokinin.
  4. Hormone That Promotes Growth of a Tendril Around a Support. Auxin.

(b) A-Pons Function: Relay centre, pneumotaxic area of respiratory centre.
B-Medulla Function: Reflex centre, cardiac centre, respiratory centre.
C-Cerebellum Function: Maintains equilibrium and coordinates muscular activities

Control and Coordination Class 10 Value Based Questions

Question 1.
How do tendrils reach the support when they do not have any sensory structures.
Answer:
Tendrils do not have any sensory structures but still they are able to find their support just as we grope in the dark for finding the switch-board. Tendrils perform circumnutation from their apical regions. In this the terminal parts of tendrils move in all directions. Wherever they come in contact with a support, they stop performing cicumnutation. Instead, the contacted region shows little growth while the other side grows rapidly so that the tendril coils over the support.

Question 2.
Name the nervous system which controls the functioning of internal organs. How does this system work ?
Answer:
Autonomous or visceral nervous system. The system does not consult the will of the individual. It works on its own inputs. Autonomous nervous system consists of only motor nerve fibres that innervate all organs and glands of the body. Depending upon the input, autonomous nervous system stimulates, slows down or stops the activity of an organ. For its working, autonomous or visceral nervous system has two components, sympathetic and parasympathetic. Sympathetic nervous system originates from thoracico-lumbar region, forms two ganglionic chains which send out long nerve fibres to various organs. The sympathetic nerve fibres activate the organs by release of nor-adrenaline. Parasympathetic nervous system is called cranio-sacral as it originates from some cranial and sacral nerves. It has long preganglionic fibres and ganglia attached to organs that are innervated. Its post ganglionic fibres secrete acetylcholine into organs for moderating or reducing their activity.

Question 3.
Which system is working when you start sweating during exercise ? What is its function ?
Answer:
Reflex activity of the nervous system. Actually 90% of nervous activity is performed through reflexes. It is automatic, involuntary and spontaneous response to a stimulus without consulting the will of the individual. Exercise increases body temperature. This can be harmful. Reflex action stimulates the sweat glands for releasing their secretion. Part of the sweat evaporates and cools, down the body.

Question 4.
You can become moody by simply switching on night bulb daily. How can this happen ?
Answer:
Night bulb reduces the secretion of melatonin hormone. Melatonin controls our day-night or circadian rhythm, healthy digestive and immune system, sexual cycle and moods. A reduced secretion causes insomnia and mood changes besides affecting health of our digestive and immune system.

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

Control and co-ordination in animals and plants: Tropic movements in plants; Introduction to plant hormones; Control and co-ordination in animals, nervous system; voluntary, involuntary and reflex action; Chemical co-ordination: animal hormones.

BoardCBSE
TextbookNCERT
ClassClass 10
SubjectScience
ChapterChapter 7
Chapter NameControl and Coordination
Number of Questions Solved26
CategoryNCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Question 1
What is the function of receptors in our body?
Solution:
Receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell.

Question 2
Draw the structure of neuron and explain its function.
Solution:
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination Q2
The specialised tips of some nerve cells detect all information from our environment. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell. This information, acquired at the end of the dendritic tip of a nerve cell, sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. This is a general scheme of how nervous impulses travel in the body. A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland. It is thus no surprise that nervous tissue is made up of an organized network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

Question 3
How does phototropism occur in plants?
Solution:
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination Q3
Phototropism is a growth movement induced by a light stimulus. Growth towards a source of light is called positive phototropism, that away from the source is termed negative phototropism. The tips of shoots are usually positively, that of roots negatively phototropic.
Charles Darwin and his son Francis discovered (in 1880) that the phototropic stimulus is detected at the tip of the plant.
The Darwins used grass seedlings for some of their experiments. When grass seeds germinate, the primary leaf pierces the seed coverings and the soil while protected by the coleoptile, a hollow, cylindrical sheath that surrounds it. Once the seedling has grown above the surface, the coleoptile stops growing and the primary leaf pierces it.
The Darwins found that the tip of the coleoptile was necessary for phototropism but that the bending takes place in the region below the tip.
If they placed an opaque cover over the tip, phototropism failed to occur even though the rest of the coleoptile was illuminated from one side.
However, when they buried the plant in fine black sand so that only its tip was exposed, there was no interference with the tropism – the buried coleoptile bent in the direction of the light.
From these experiments, it seemed clear that

  • The stimulus (light) was detected at one location (the tip)
  • The response (bending) was carried out at another (the region of elongation).
  • This implied that the tip was, in some way, communicating with the cells of the region of elongation.

Question 4
How does chemical coordination occur in plants?
Solution:
It has been found that the growth of plants is regulated by certain chemical substances which are synthesized by the plants in very small amounts. These are known as plant hormones or phytohormones.

They are the organic substances which either promote or inhibit growth. A phytohormones can be defined as a chemical substances which are produced naturally in plants and are capable of translocation and regulating one or more physiological processes when present in low concentration. Main categories of plant hormones are:

  1. Auxins
  2. Gibberellins
  3. Cytokinins
  4. Ethylene
  5. Abscisic acid

Auxins and Gibberellins stimulate cell elongations, cytokinins stimulate cell division ethylene promotes transverse or isodiametric growth and abscisic acid is a growth inhibitor.

Question 5
What is the need for a system of control and coordination in an organism?
Solution:
Co-ordination in this sense refers to the regulation or control of body activity.
Plants need very little in the way of a control system. Since growth and reproduction are about the only things that are regulated, a rapid control system is not required and hormonal control is all they possess.

Animals are continually moving through new environments that may pose all types of changes and threatening situations to the organism. This requires the rapid and precise control of a nervous system. Hormones regulate slower activities, such as growth, development and reproduction.

Question 6
How are involuntary actions and reflex actions different from each other?
Solution:
All reflex actions are involuntary in nature but all involutary actions are not reflexes as the beating of heart is an involuntary action but is not reflex action.

Reflex actions are very quick but all involutary actions may not be very fast as in heart beating.
A reflex action may involve any muscle or a gland as we withdraw our hand on touching a hot object but all involuntary actions involve only smooth i.e., involuntary or cardiac muscles.

Reflex actions are at the level of spinal cord whereas the involuntary actions generally involve brain too.
Nerves and autonomious nervous system can increase or decrease the rate of involuntary actions but reflex actions can be controlled by great will only and are not usually controllable.

Reflex actions are done to meet emergencies where as an inv.action may or may not be for just meeting an emergency but may be a critical lie process as circulation of blood, swallowing of food, movement of food in food pipe, etc.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
What is the correct direction of flow of electrical impulses ? [NCERT Exemplar]
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination MCQs Q1
Answer:
(c) Direction of flow of electrical impulse.
Impulse → Dendrite → Cell body → Axon → Release of chemicals that cross synapse → Dendrite of next neuron.

Question 2.
Three directions in which nerve impulses can travel in the nervous system are listed below:
(i) Away from the central nervous system
(ii) Towards the central nervous system
(iii) Within the central nervous system
In which direction do impulses in sensory and relay (intermediate) neurons travel?

Sensory NeuronRelay
Neuron
(a)(i)(ii)
(b)(i)(iii)
(c)(ii)(i)
(d)(ii)(iii)

Answer:
(d) Sensory neuron transmits impulses towards CNS, (i.e. brain and spinal cord) while, the relay neurons occur within the CNS and serve as links between other neurons.

Question 3.
In a nerve pathway, the following events take place in a coordinated order.
(i) Activation of muscle
(ii) Activation of receptor
(iii) Passage of impulses along a motor neuron
(iv) Passage of impulses along a sensory neuron
Read the events given and identify the correct order of these events from the table given below:

FirstLast
(a)(ii)(iii)(iv)(i)
(b)(ii)(iv)(iii)(i)
(c)(iv)(i)(iii)(ii)
(d)(iv)(ii)(i)(iii)

Answer:
(b) The sequence of events in a typical nerve pathway is receptor → passage of impulse along sensory neuron → passage of impulse along motor neuron →  activation of muscle (effector). Thus, the correct sequence is (ii), (iv), (iii) and (i).

Question 4.
The diagram shows a section of the brain and different parts labelled as W,X, Y and Z.
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination MCQ Q4
Study the figure and correlate the regions which control balance, heart rate and temperature in human body?

BalanceHeart RateTemperature
(a)WZX
(b)XYZ
(c)YXW
(d)ZWY

Answer:
(b) Out of the options given, the region X, (i.e. cerebellum) controls balance, region Y (i.e. medulla oblongata) controls heartbeat and region Z, (i.e. hypothalamus) controls temperature in human body.

Question 5.
Which of the following endocrine glands is unpaired? [NCERT Exemplar]
(a) Adrenal
(b) Testes
(b) Pituitary
(d) Ovary
Answer:
(c) There are two adrenal glands, one on top of each kidney that make adrenaline hormone. Testes are paired glands present in males and secrete male sex hormone. Pituitary gland is present just below the brain and is unpaired. It is also called master gland as it secretes a number of hormones. Ovaries are paired glands present in females and secrete female sex hormones.

Question 6.
Dramatic changes of body features associated with puberty are mainly because of secretion of [NCERT Exemplar]
(a) oestrogen from testes and testosterone from ovary
(b) oestrogen from adrenal gland and testosterone from pituitary gland
(c) testosterone from testes and oestrogen from ovary
(d) testosterone from thyroid gland and oestrogen from pituitary gland
Answer:
(c)

GlandHormoneFunction
Testes
(only in
males)
TestosteroneTo control the development
of male sex organs and male features such as deep voice, etc., i.e. changes associated with puberty.
Ovaries
(only in
females)
OestrogenTo control the development
of female sex organs and
female features such as soft skin, etc.
ProgesteroneTo control uterus changes during menstrual cycle and helps in maintenance of pregnancy.

Class 10 Science Control and Coordination Mind Map

Coordination is the process through which two or more organs interact and complement the functions of one another. The neural system & endocrine system jointly coordinate & regulate the physiological functions in the body. The neural system provides an organised network of point-to-point connections for a quick coordination. The endocrine system provides chemical integration through hormones.

Animal Nervous System
The neural system of all animals is composed of highly specialized cells called neurons which can detect, receive & transmit different kinds of stimuli. They are specialized for conducting information via electrical impulses from one part of the body to another.

Structure and Function of Neuron

  • It is a structural & functional unit of neural system and is composed of three major parts:
  • Ceil body contains cytoplasm with typical cell organelles like nucleus etc.
  • Dendrites: Short fibres which branch repeatedly & project out of the cell body. These fibres transmit impulses towards the cell body.
  • Axon is a long fibre, the distal end of which is branched and forms nerve ending. Nerve endings possess synaptic vesicles containing chemicals called neurotransmitters.

Transmission of impulses:

  • Stimulus or information from the environment is detected by specialized tips of some nerve cells called as receptors.
  • Dendritic tip acquire all these information and sets off a chemical reaction.
  • This chemical reaction then creates an electric impulse that travels from the dendrite to the cell body, and then along the axon to its end.
  • At the end of the axon, the electrical impulse sets off the release of some chemicals (neurotransmitters). These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.
  • A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland.

The human neural system is divided into two parts:

  • Central neural system (CNS) includes the brain & spinal cord and is the site of information processing & control.
  • Peripheral neural system (PNS) comprises of all nerves of body associated with CNS (brain and spinal cord). The nerve fibres of PNS are of two types: cranial nerves (arising from the brain) and spinal nerves (arising from the spinal cord).

Brain

  • It is the main coordinating centre of the body. The bra in and spinal cord constitute the CNS. They receive information from al 1 parts of the body and integrate it.
  • The brain is located in bony box called as cranium or skull which protects the brain. Spinal cord is protected with the help of vertebral column. In addition, cerebrospinal fluid also covers the brain and the spinal cord which provide the function of shock absorption.
  • The brain has three such major parts or regions, namely the fore-brain, mid-brain and hind-brain.
  • Fore-brain: It is the main thinking part of the brain. It consists of cerebrum, hypothalamus etc.
    • Function: interpret information received from sensory receptors.
    • Control the movement of voluntary muscles.
    • It also contains centre associated with hunger which gives us the sensation of feeling full.
  • Midbrain: It serves important function in few involuntary movements, movements of the eye, auditory and visual processing.
  • Hindbrain: It consists of pons, medulla, and cerebellum.
    • Function: Medulla controls involuntary actions such as blood pressure, salivation and vomiting.
    • Cerebellum is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

Reflex Action

  • The entire process of response to a peripheral nervous stimulation that occurs involuntarily (without conscious effort or thought) and requires the involvement of a part of central nervous system is called a reflex action.
  • Reflex action decreases the duration of action by bypassing the thinking and processing step.
  • It does so by linking the nerves carrying the signal (say the sensation of heat) directly to the nerves that move the muscle. These types of linkage or connection between input and output nerves are formed in the spinal cord.
  • These connections are called as reflex arc (sensory/input nerve-* Spinal cord -> motor/ output nerve)

Coordination In Plants

Plants have neither nervous system nor muscles. Their movements or responses are either growth dependent or growth independent.

Immediate Response To Stimulus Or Growth Independent

The plants also use electrical-chemical means to convey information from cell to cell, but unlike in animals, there is no specialised tissue in plants for the conduction of information.

Secondly, plant cells change shape by changing the amount of water in them, resulting in swelling or shrinking. In contrast, animal muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses.

Example: folding up and drooping of leaves of chhui-mui (the ‘sensitive’ or ‘touch-me-not’ plant of the Mimosa family) in response to touch.

Movement Due To Growth

The movement of a plant in response to the stimulus is called as tropism. The movement in the direction of the response is called as positive tropism and movement away from the stimulus is termed as negative tropism.

Types:

  • Phototropism: Bending of plant in response to the light e.g. movement of sunflowers in response to day or night.
  • Geotropism: Movement of plant in response to gravity. Shoots show negative geotropism and roots show positive geotropism.
  • Chemotropism: Movement of plant in response to chemical as observed in case of growth of pollen tube.
  • Hydrotropism: e.g. roots beneath the Earth’s surface bend in the direction of underground w^ater.
    Other example may include the climbing of tendrils in response to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus cling to it.

Plant Hormones

There are five main types of plant hormones or growth regulators:

  • Auxins: Helps in cell elongation and thus phototropism, geotropism, and other plant responses.
  • Gibberellins: Stimulate growth of the stem and flowering.
  • Cytokinins: They cause cell division, enlargement, and organ formation. They are present in greater concentration in areas of rapid cell division, such as in fruits and seeds.
  • Ethylene: Promotes ripening of fruits.
  • Abscisic acid: Inhibits growth and causes wilting of leaves and fruits.

Hormones In Animals

Hormones are non-nutrient chemicals which act as intercellular messengers & are produced in trace amounts. The timing and amount of hormone released are regulated by feedback mechanisms Examples:

  • Adrenaline: Secreted from adrenal gland which prepare the body for fight or flight situation.
  • Thyroxin: Secreted from thyroid gland and regulates carbohydrate, protein and fat metabolism so as to provide the best balance for growth.
    Deficiency of iodine in diet may cause hypo-secretion of thyroxin which results in goiter.
  • Growth hormones which regulate growth and. development of the body are secreted from
    pituitary gland.
    Hyper-secretion may cause gigantism and hypo-secretion may cause dwarfism.
  • Testosterone in males and oestrogen in females lead to changes take place during puberty’.
  • Insulin produced by pancreas regulates the blood sugar level in the body.
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination Mind Map 1

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination (Hindi Medium)

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NCERT Solutions for Class 10 Science Chapter 7
NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination
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10 Science Chapter 7 page 138 Answers
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