CBSE Class 10

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

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 16 Management of Natural Resources. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Biology) Chapter 16 – Management of Natural Resources solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 16 – Management of Natural Resources Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Questions

In Text Questions

Question 1.
What changes would you make in your habits to become environment friendly ? (CBSE AI 2009)
Answer:
Three Rs — reduce, recycle and reuse.

1. Reduce: It is to reduce consumption by preventing wastage.
   1. Switching off unnecessary lights, fans and other electrical appliances,
   2. Repair of leaky taps.
   3. Reducing food wastage,
   4. Walking down to nearby market instead of using vehicle.
2. Recycle: Separation of recyclable wastes from non-recyclable wastes. The former are taken by rag pickers for sending them to industries involved in recycling, e.g., paper, plastic, metal, glass.
3. Reuse: Carry bags, packing material, plastic containers and other reusable articles should not be thrown away if the same are uncontaminated. For example, plastic bottles and jars containing various food items brought from market can be washed and used for storing things in the kitchen.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
What would be advantages of exploiting resources with short term aims ?
Answer:

1. All the commodities for use and comforts for human society will become available in plenty.
2. There will be rapid industrialisation and development.

Question 3.
How would these advantages differ from the advantages of using a long term prospective in managing our resources ?
Answer:

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:
Need for Equitable Distribution. Resources are living and non-living components of nature which are drawn upon to provide food, fodder, shelter, water, energy, articles of daily use and comforts. Every human being has the fundamental right to obtain and use the same. This is possible only when there is equitable distribution of resources.
Forces Against Equitable Distribution,

1. Restricted availability of resources,
2. Excessive consumption by the rich,
3. Profit motto by the persons exploiting resources.

Question 5.
Why should we conserve forests and wildlife ?
Answer:
There are economic and ecological reasons to conserve forests and wildlife.

1. Economic Reasons:
   1. Forests are a source of shelter, food and fodder to people living in and around forests,
   2. They provide firewood and timber,
   3. A number of industrial raw materials are obtained from forests, e.g., tannins, dyes, resins, perfumes, wood for paper,
   4. Several medicines are got from forest plants and animals,
   5. Wildlife is a gene bank for improvement of domesticated plants and animals,
   6. All plants and animals have not yet been explored for their potential uses.
2. Ecological Reasons:
   1. They regulate climate,
   2. Forests help in retaining rain water and its storage in aquifers from where water becomes available to springs and streams,
   3. Forests control soil erosion and prevent the occurrence of floods,
   4. Wildlife is essential for maintaining the forests.
   5. CO₂-O₂ balance is maintained.

Question 6.
Suggest some approaches towards the conservation of forests.
Answer:
Conservation is protection, augmentation and scientific management of a resource so as to maintain it at its optimum level while providing sustainable benefits for the present as well as future generations. Some approaches for conservation of forests are as follows :

1. Afforestation and Reforestation. Afforestation is developing forest over an area where none existed earlier. Reforestation is developing forest cover which has been cleared during exploitation. Degraded forests are also mended to bring them back to health. All this is done by state forest department either by themselves or with the help of joint forest management committees.
2. Separation of Commercial Forestry. Useful plants required for meeting commercial needs should be planted separately so that there is no undue pressure on natural forests. Social forestry is growing multipurpose plants on village common lands for meeting requirement of fodder, firewood and small timber. Production plantation is growing industry required plants on wastelands.
3. Controlled grazing.
4. Prevention of scraping and litter removal.
5. Practising block cutting or cutting of forest equal to its regeneration capacity.
6. Building of national parks, sanctuaries and biosphere reserves.

Question 7.
Find out about traditional systems of water harvesting management in your region.
Answer:
Ponds, pools, tanks, lakes, ditches and wetlands. They get filled up during rain. Larger reservoirs are perennial. The smaller ones dry up after a few months. However, both help in recharge of ground water.

Question 8.
Compare the above system with the probable system in hilly/mountainous areas or plains or plateau regions.
Answer:
Hilly/Mountainous Areas. Water is impounded on the slopes, at the base of slope, on the border of ravine or melting snow into tanks called Kulhs, Khatris, Kuls (Himachal Pardesh, J and K), Zabo (Nagaland) and Zings (Ladakh). Water from tanks is used for different purposes—drinking, washing, animals, irrigation.
Plains,

1. Roof top harvesting of rain water has been in practice since ages in Rajasthan. The collected water is stored below the ground level for later use.
2. Other methods of water harvesting are specially constructed tanks, Kuis, jhaslars, booris or bers, paar, vivdas, khadins and nadis (Rajasthan), ponds in Kandi belts (Jammu), bhandaras and tals (Maharashtra), bundhis (MP and UP), ahars and pynes (Bihar).
   Plateau. Water is collected in series of tanks through impounding rain water, building check dams and channels from flowing water. They are called eris (Tamil Nadu), surrangams (Kerala) and kattas (Karnataka).

Question 9.
Find out the source of water in your region!locality. Is water from this source available to all people living in that area ?
Answer:
Water is supplied by municipal corporation through pipes. It is obtained from river/canal (if the same happens to be nearby). In many cases piped water is pumped out from ground by tube wells and stored in raised water tanks.
Municipal water supply is not available to all the residents. Many newly built colonies, slums and unauthorised localities are often without the piped water.

NCERT Chapter End Exercises

Question 1.
What changes would you suggest in your home in order to be environment friendly ?
(CBSE AI 2009, CCE 2012, 2014)
Answer:

1. Judicious use of electricity by switching off lights and electrical appliances not required,
2. Replacement of incandescent bulbs with fluorescent, compact fluorescent ones and LED bulbs.
3. Replacement of electricity or gas operated geysers with solar water heaters,
4. Replacement of electricity generating sets with solar light,
5. Having more natural light and ventilation with design supporting warming during winters and cooling during summer,
6. Reducing wastage of water, food and other articles.
7. Separation of recyclable waste from non-cyclable waste prior to disposal.
8. Increasing reuse of containers,
9. Using cloth bags instead of polythene, plastic or paper bags.

Question 2.
Can you suggest some changes in your school which would make it environment friendly ?
Answer:
Yes.

1. Rainwater harvesting (RWH) by draining roof top rain for underground seepage,
2. Plantation of trees and shrubs along the boundary for protection against noise and air pollution. Plants will not only provide more oxygen during the school hours but also have a moderating effect on climate.
3. Prevention of wastage of electricity and water,
4. Having compost pits for conversion of plant refuse and other biodegradable wastes into useful resource,
5. Increasing use of solar energy,
6. Activating ecoclub.

Question 3.
There are four main stakeholders when it comes to forests and wildlife. Which among these should have the authority to decide the management offorest produce ? Why do you think so (CBSE Foreign 2010, CCE 2011)
Answer:
The four stakeholders in forests and wildlife are

1. People living in and around forests who obtain most of their requirements from forests,
2. Forest department which owns the forests.
3. Industrialists who obtain raw materials for their industries,
4. Wildlife and nature enthusiasts. Among them the persons living in and around the forests have traditional knowledge of how best the forests can be managed so that a sustainable yield can be obtained indefinitely. Therefore, authority for management of forest produce should be handed over to them. However, the forest department must monitor the same so that there is no excessive exploitation.

Question 4.
How can you as an individual contribute or make a difference to the management of
(a) Forests and wildlife
(b) Water resources
(c) Coal and petroleum ?
Answer:
(a) Forests and Wildlife:

1. I will stress on sustainable use of produce from forests and wildlife,
2. The area under forest cover has to be increased to control global warming.
3. Form more joint forest management committees,
4. Separate commercial forestry from natural forestry.

(b) Water Resources. My major stress will be

1. Recharging of ground water through rain water harvesting, protection to wetlands and digging sponge pits or wells in the beds of rivulets,
2. Reducing spoilage of water in agriculture by helping formers to switch over to sprinkler system of irrigation, changing conventional method of rice cultivation with system of rice intensification (SRI),
3. Judicious use of water for domestic and industrial purposes.

(c) Coal and Petroleum:

1. Higher level of purification to reduce pollution,
2. Increased use of solar energy,
3. More investment to commercialise hydrogen powered transport system.

Question 5.
What can you, as an individual, do to reduce your consumption of various natural resources ?
Answer:
Follow the principle of three Rs, i.e, reduce, recycle, reuse.

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) Conservation of Natural Resources

1. Reduced consumption of electricity by switching off unwanted fans and bulbs,
2. Reduced consumption of water by closing the tap to prevent overflow of water in the bucket during taking bath,
3. Used refills instead of purchasing new pens,
4. I did not waste food,
5. I have started going to school by school bus instead of using car.

(b) Increase Pressure on Natural Resources

1. While reading at night on bed, I fell asleep and forgot to switch off the lights,
2. While brushing my teeth and later taking bath, I did not close the tap, so a lot of water was wasted,
3. I left the ball pen uncapped, so the ink dried up. I had to throw three ball pens last week,
4. I am in the habit of using loose sheets for doing rough work. They are then thrown away,
5. I bring more food in my tiffin than I eat. Daily I throw a lot of food in the dust bin.

Question 7.
On the basis of environmental issues you studied, what changes would you incorporate in your life style in a move towards a sustainable use of our resources ?
Answer:
1. Follow the principle of three Rs — reduce, recycle and reuse.
2. Undertake tree plantation twice a year during days of Van Mahotsava.
3. Where possible, use of public transport, school, bus and car pools.
4. Use of solar energy for as many purposes as possible.

Selection Type Questions

Alternate Response Type Questions
(True/False, Right(√)/Wrong (x), Yes/No)

Question 1.
Presence of coliform bacteria in a water body indicates contamination by industrial effluents.
Question 2.
An environmentally friendly decision is reuse jam and pickle bottles.
Question 3.
Forests are reservoirs of wildlife.
Question 4.
Chipko andolan originated in Haridwar during 1980s.
Question 5.
Check dams are built along seasonal flooded gullies for water harvesting.
Question 6.
Coal and petroleum are non-renewable inexhaustible resource.
Question 7.
An important protective function of forests is reduction of atmospheric pollution.
Question 8.
Forest department has been able to maintain biodiversity by growing pine, Teak and Eucalyptus on large tracts.

Matching Type Questions

Question 9.
Match the columns I and II (single matching) :

Question 10.
Match the contents of columns I, II and III (double matching) :

Question 11.
Mark the resource as I (inexhaustible), R (renewable) and N (non-renewable) (key or check list items):

Question 12.
Match stimulus with appropriate response.

Fill in the Blanks

Question 13. Forests are ………….. hot spots.
Question 14. Amrita Devi Bishnoi sacrificed her life and that of 363 others in for ……………….. protection of …………….. trees.
Question 15. In blood carbon monoxide forms …………… that is unable to transport oxygen.
Question 16. Ganga runs its course of 2500 km from …………….. in Bay of Bengal.
Question 17. To save energy and prevent warming, I use ……………… instead of incandescent bulbs.

Answers:

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

Hope given NCERT Solutions for Class 10 Science Chapter 16 are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 15 Our Environment. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Biology) Chapter 15 – Our Environment solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 15 – Our Environment Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Questions

In Text Questions

Question 1.
Why are some substances biodegradable and some non-biodegradable ? (CCE 2011)
Answer:
Biodegradable substances are substances of organic origin which can be broken down by enzymes of saprophytes, e.g., garbage, sewage, livestock waste, agriculture waste. Non-biodegradable substances are man-made substances which cannot be degraded by saprophytes because they lack the enzymes to do so e.g., waste plastic and polythene articles.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2..
Give any two ways in which biodegradable substances would affect the environment.
(CBSE Delhi 2007, AI 2009 C)
Answer:

1. Stink: Within a day or so waste biodegradable substances begin to stink and produce foul gases.
2. Pests and Pathogens: The decaying biodegradable substances become breeding places of flies and many other pests. They also contain a number of pathogens. Flies and other pests carry the germs to all the places visited by them resulting in spread of diseases.

Question 3.
Give any two ways in which non-biodegradable substances would affect the environment. (CBSE AI 2009 C)
Answer:

1. Dumping Area: Dumping of non-biodegradable substances on a piece of land converts the same into barren land. It is also called landscape pollution.
2. Biological Magnification: Pesticides, heavy metals and other chemicals enter water and food chains. They accumulate in toxic proportions and harm all kinds of living organisms. Their concentration also increases with rise in trophic level. Human beings are harmed the most because man lies at the top of every food chain.

Question 4.
What are trophic levels ? Give an example of a food chain and state the trophic levels in it.
Answer:
(a) Trophic Levels. They are steps or divisions of food chain which are characterised by particular methods of obtaining food, e.g., producers (T₁), herbivores (T₂), primary carnivores (T₃), etc.

(b) Flow of Energy Through Food Chain. Energy enters a food chain through producers. Producers or green plants trap solar energy and convert it into chemical energy of food during photosynthesis. From producers energy passes into herbivores. A lot of energy dissipates during transfer and utilization of food energy by herbivores (10% law). From herbivores the food energy passes into primary carnivores, again with a lot of dissipation. Only about 10% of herbivore energy is passed into body mass of primary carnivores. From primary carnivores, nearly 10% energy passes into secondary carnivores and so on. It is ultimately lost as heat.

Question 5.
What is the role of decomposers in the ecosystem ?
Answer:
Ecosystem is a self-contained ecological system which consists of a distinct biotic community and the physical environment, both interacting and exchanging materials between them. It is a structural and functional unit of biosphere. Ecosystem is an open system which requires a regular input of energy and circulation of matter for its sustenance. Different ecosystems are in contact with one another. Though they are distinct, but exchange of materials can occur amongst them. Ecosystem can be small (e.g., rotting piece of wood) or large (e.g., forest, ocean), temporary (e.g., rain fed pond) or permanent (e.g., lake, forest), natural or artificial.
Natural Ecosystems: They are ecosystems which develop in nature without human support. Natural ecosystems are of two types, terrestrial and aquatic. Terrestrial ecosystems occur over land. They are of three major types -— desert, grassland and forest. Aquatic ecosystems are found in water bodies, e.g., ponds, lakes, rivers (fresh water), estuaries, marine (salt water).
Artificial Ecosystems: They are ecosystems which have been p/g. 5.7. An aquarium. created and are maintained by human beings. Artificial ecosystems are also called man-made or anthropogenic ecosystems. Agroecosystem is the largest man-made ecosystem. Garden is a common artificial ecosystem maintained by most institutes. It has various types of plants grown and maintained by gardener — grass, trees, flower bearing plants like Rose, Jasmine, Sunflower. A number of animals become residents and visitors of the garden. Aquarium is another artificial ecosystem.

Question 6.
What is ozone and how does it affect any ecosystem ?
Answer:
Definition of Ozone: Ozone is a triatomic molecule made up of three atoms of oxygen, O₃.
Effect:

1. Protection against ultraVoilet rays if present in stratosphere,
2. Ozone dissipates the energy of ultraviolet rays by undergoing dissociation following by reassociation
   

If present in the atmosphere of ecosystem, it is highly toxic causing injury to mucous membranes, eye irritation and internal haemorrhages in animals and humans. It harms plants by destroying photosynthetic cells producing necrosis.

Question 7.
How can you help in reducing the problem of waste disposal ? Give any tivo methods.
Answer:
Waste disposal is becoming the biggest problem of all local bodies. It is consuming a big chunk of their revenues. Even then the points of collection are turning into stinking areas. Transport of waste to disposal site is seldom perfect. There is stink all the way. A lot of waste is thrown on the roads by the vehicles carrying the waste.
The quantity of waste can be reduced if you form the habit of separation of waste into biodegradable and non-biodegradable parts.

1. Non-biodegradable Waste. Most often the non-biodegradable waste is recycled. It is taken away by rag pickers.
2. Biodegradable Waste. Biodegradable waste is putressible. It can be composted or vermicomposted to prepare compost for your kitchen gardens. The technique can also be used in schools and other institutions. Some institutes in big cities have installed incinerators for disposal of combustible components of waste. Hospital waste is being compulsorily incinerated to reduce contamination and spread of diseases.

NCERT Chapter End Exercises

Question 1.
Which of the following groups contains only easily biodegradable items ?
(A) Grass, flower and leather
(B) Grass, wood and plastic
(C) Fruit peels, cake and lime juice ,
(D) Cake, wood and grass.
Answer:
(A), (C), (D).

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).

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 the above.
Answer:
(D).

Question 4.
What will happen if you kill all the orgainsms in one trophic level ?
Answer:
Higher Trophic Level. All the organisms will be starved and die. Lower Trophic Level. The organisms will increase in number much beyond the carrying capacity of the enviroment. They will become weak and fall easy prey to various diseases, ultimately resulting in decline in population. The ecosystem may get converted into a desert.

Question 5.

1. Will the impact of removing all the organisms in a trophic level be different for different trophic levels ?
2. Can the organisms of any trophic level be removed without causing any damage to the ecosystem ?

Answer:

1. Yes. Impact of removing all the organisms of a trophic level depends upon the trophic level. Removal of producers will kill all the consumers. Killing of carnivores will increase the number of herbivores which in turn will eat up all the producers. They would themselves die of starvation. However, if herbivores are removed, all the carnivores of the area will die. The plants which are dependent upon animals for pollination will fail to reproduce and die ultimately. Others would persist and increase in number, again much beyond the carrying capacity of the environment.
2. No. Removal of all the organisms of a trophic level will disturb the ecosystem – killing of higher trophic level organisms and explosion in populations of lower level organisms. Higher number of lower trophic level organisms will adversely affect the ecosystem by consuming whole or major part of their prey.

Question 6.
What is biological magnification ? Will the levels of this magnification be different at different levels of the ecosystem ?
Answer:
Definition: Biological magnification is increase in the concentration of a chemical per unit weight of the organisms with the successive rise in trophic level. In one study it was found that concentration of harmful chemical like DDT will increase 80,000 times the concentration present in water.
Levels of Magnification at Different Levels of Ecosystem. Levels of biomagnification of a chemical will be different at different levels of ecosystem. In one study it was found that concentration of a pesticide was 0.002 ppm in water, 0.05 ppm in plankton, 2.4 ppm in fish and 16.0 ppm in fish eating bird.

Question 7.
What are the problems caused by the nonbiodegradable waste we generate ?
Answer:

1. Volume: Being non-biodegradable, the volume of these wastes will not decrease by natural process of decomposition.
2. Land Use: They have to be dumped over land. The land becomes unfit for any other purpose.
3. Heavy Metals: Heavy metals present in industrial wastes (e.g., copper, lead, chromium, nickel, mercury) remain in the soil indefinitely. Slowly they pass into vegetation and crops harming both humans and animals.
4. Pesticides and Other Toxins: They pollute underground water, surface water and soil. The chemicals enter food chain and become concentrated, harming animals and humans.
5. Rag Pickers: In the process of removing recyclable materials from solid wastes, the rag pickers are exposed to many diseases and toxins.
6. Recycling: Recycling of materials produces only’inferior quality products. Recycling of polythene and plastic is accompanied by release of carcinogenic toxins like dioxins and furans.

Question 8.
If all the waste we generate is biodegradable, will this have no impact on the environment ?
Answer:
The impact on the environment will depend upon the system of collecting, transporting and disposal of biodegradable waste. If it is regular and clean, the impact will be little in urban areas. Only some effect will be observed at disposable site which will emit foul gases and expose the sanitary workers to contamination. The same can also be reduced by increased use of machines and wearing of protective gear by the sanitary workers.

Question 9.
Why is damage to the ozone layer a cause of concern What steps are being taken to limit this damage ?
Answer:
Cause of Concern: Ozone layer present in the stratosphere has thinned out by about 8% over the equator and more so over the antarctica where a big ozone hole appears every year.
This has increased the level of UV-B radiations reaching the earth by 15-20%. These radiations are causing increased number of skin cancers, cataracts and reduced immunity in human beings. There is increased incidence of blinding of animals, death of young ones, reduced photosynthesis, higher number of mutations and damage to articles.
Steps to Limit Damage:

1. Ban on production and use of halons.
2. Ban on production and use of chlorofluorocarbons.

Selection Type Questions

Alternate Response Type Questions
(True/False, Right(√)/Wrong (x), Yes/No)

Question 1.
Wastes are of two types, biodegradable and non-biodegradable.
Question 2.
Non-biodegradable articles are the ones which cannot be digested.
Question 3.
Ozone is formed in stratosphere by action of ultravoilet radiations on oxygen.
Question 4.
Earth is kept warm due to green house flux.
Question 5.
Rag pickers remove reusable articles.
Question 6.
Pyrolysis is aerobic combustion while incineration is anaerobic combustion.
Question 7.
Biodegradable wastes should be separated and kept in blue colour bins for garbage collectors.
Question 8.
Food web ensures survival of all types of trophic levels.

Matching Type Questions

Question 9.
Match the articles in columns I and II (single matching) :

Question 10.
Match the contents of columns I, II and III (double matching)

Question 11.
To what trophic level (T₁, T₂, T₃, T₄) do the following belong (key or check list items)

Question 12.
Match each stimulus with appropriate response :

Fill In the Blanks

Question 13. Waste substances that are broken down by microbes are called ………. : ………… .
Question 14. Gardens and crop fields are ………………. ecosystems.
Question 15. Microorganisms are called ……………… as they break down the complex organic remains into simple inorganic substances.
Question 16. Decrease in ozone in stratosphere is linked to release of synthetic chemicals like ……………… .
Question 17. Improvement in life style often results in increased generation of …………. : ………… material.

Answers:

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Hope given NCERT Solutions for Class 10 Science Chapter 15 are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Physics) Chapter 14 – Sources of Energy solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 14 – Sources of Energy Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Questions

In Text Questions

Question 1.
What is good source of energy ?
Answer:
A substance which produces sufficient amount of energy over a long period of time without producing much smoke is known as good source of energy. Characteristics of a good source of energy.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
What is good fuel ?
            Or
What is a fuel ?
Answer:
A fuel which provides large amount of heat energy without causing pollution.

Question 3.
If you could use any source of energy for heating your food, which one would you use and why ?
Answer:
We would use microwave oven for heating our food. This is because the nutritional value of food is not lost when heated in a microwave oven.

Question 4.
What are the disadvantages of fossil fuels ? (CBSE 2010)
Answer:

1. They cause environmental pollution.
2. They cause global warming.
3. They do not supply enough heat energy.
4. The by-products of burning fuels cause acid rain which pollute water resources.

Question 5.
Why are we looking at alternate sources of energy ?
                                                      Or
State one reason that has necessitated to look for alternate sources of energy ? (CBSE 2013)
Answer:
Because the conventional sources of energy may completely be exhausted one day if their use at the present rate continues.

Question 6.
How has the traditional use of wind energy and water been modified for our convenience
(CBSE 2010, Term I)
Answer:
These energies have been converted into electrical energy using electric generators.

Question 7.
What kind of mirror—concave, convex or plane would be best suited for the use in a solar cooker. Why ?
Answer:
Concave mirror, because it focusses the sun rays at a point to raise the temperature at that point.

Question 8.
What are the limitations of the energy that can be obtained from oceans ? (CBSE 2010)
                                                      Or
List any four limitations of the energy obtained from oceans. [CBSE (All India) 2009, 2012]
Answer:

1. Energy from oceans is available only when high tides are in the ocean.
2. Power plants used to convert ocean energy into electric energy do not operate continuously.
3. Energy of ocean waves can be extracted blow all times across the ocean.
4. Tidal power plants can not be installed everywhere.

Question 9.
What is geothermal energy ? (CBSE 2010, Term I, 2011, 2012)
Answer:
The heat energy stored in the hot spots of the earth’s crust is called geothermal energy.

Question 10.
What are the advantages of nuclear energy ?
Answer:

1. A small quantity of nuclear fuel gives a large amount of energy.
2. In a nuclear power plant, the nuclear fuel is inserted once to get energy over a longer period of time.

Question 11.
Can any source of energy be pollution free ? Why or why not ?
Answer:
No source of energy is there which is pollution free. However, some sources of energy cause more pollution and some sources of energy cause less pollution.

Question 12.
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not ?
Answer:
Hydrogen causes less air pollution than C.N.G. because burning of hydrogen produces water vapours and burning of CNG produces CO₂. When the concentration of CO₂ increases in the atmosphere, then the temperature of the atmosphere increases. This effect is known as green house effect. The increased temperature of the atmosphere affects life on the earth.

Question 13.
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer:

1. Bio-mass is considered as a renewable source of energy because forests can be replenished.
2. Water is also a renewable source of energy as water is continuously available to use due to water cycle in nature.

Question 14.
Give the names of two energy sources that you would consider to be exhaustible.
Answer:
Give reasons for your choices,

1. Coal
2. Petroleum.

They will be exhaustible when continuously extracted. Moreover, the formation of these fuels under the earth takes a longer period of time.

NCERT Chapter End Exercises

Question 1.
A solar 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).

Question 2.
Which of the following is not a example of a bio-mass energy source ?
(a) wood,
(b) gobar gas,
(c) fossil fuels,
(d) bio-mass. (Bihar Board 2012)
Answer:
(c).

Question 3.
Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Suns energy ?
(a) geothermal energy,
(b) wind energy,
(c) fossil fuels,
(d) bio-mass.
Answer:
(a).

Question 4.
Compare and contrast fossil fuels and the Sun as a source of energy.
Answer:

1. Energy of fossil fuels comes from the solar energy. However, fossils fuels are the non-renewable sources of energy. On the other hand, sun is a renewable source of energy.
2. Fossil fuels cause pollution but solar energy does not cause pollution.
3. Energy is supplied by fossil fuels at any time of the day but sun supplies energy only when it shines.

Question 5.
Compare and contrast bio-mass and hydro-electricity as source of energy.
Answer:

Question 6.
What are the limitations of extracting energy from
(a) the wind
(b) Waves
(c) Tides ?
Answer:
(a)

1. We cannot depend upon wind energy as it is available only when strong wind blows. The appliances or machines operating with wind energy stop working as soon as wind stops. The minimum speed of wind to operate generator to produce electricity is 15 km/h.
2. Wind energy is not sufficient to operate heavy machines.
3. The use of wind energy is limited to certain places where strong winds blow most of the time.

(b) Energy of waves can be extracted only if strong winds blow all the time across the sea.
(c) Tidal power plant can extract energy from the waves only when the difference between the water levels of high tide and low tide is very large.

Question 7.
On what basis you classify energy source as
(a) Renewable and non-renewable ?
(b) Exhaustible and inexhaustible ?
(c) Are the options given in (a) and (b) the same ?
Answer:
(a) Renewable Sources of Energy are those which are continuously supplied by nature. For example, the sun, the wind.
(b) Non-Renewable Sources of Energy are those which have been formed in nature long ago under certain conditions of temperature and pressure. Non-renewable sources of energy take longer period of time for their formation. For example, fossil fuels like coal, petroleum.
(c) Inexhaustible Sources of Energy are those which supply continuous energy for unlimited time. In fact, exhaustible sources of energy are also termed as non-renewable energy sources. But wood is an exception as it can be made renewable by growing more plants periodically. Inexhaustible sources of energy are termed as renewable sources of energy.

Question 8.
What are qualities of an ideal source of energy ?
                                               Or
Write any two characteristics of a good source of energy. (CBSE 2013)
Answer:

1. It supplies useful energy continuously.
2. It does not cause environment pollution.
3. It is economical.

Question 9.
What are the advantages and disadvantages of using a solar cooker ? Are there places where solar cookers would have limited utility ? (CBSE 2010)
Answer:
Advantages:

1. There is no cost of cooking food in a solar cooker.
2. No pollution is caused when food is cooked in a solar cooker.
3. Nutrition value of food is preserved when food is cooked in the solar cooker.
4. Two or three dishes can be cooked at a time.

Disadvantages:

1. Food cannot be cooked at night and on a cloudy day using a solar cooker.
2. The cost of making solar cooker is high.
3. Food cannot be cooked quickly with the solar cooker.
4. Large quantity of food cannot be cooked with a solar cooker.
5. Chapatis cannot be made with solar cooker.
   Solar cooker will have limited utility at places where the sun shines for shorter period of time or where the sun rays never reach.

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

1. More use of fossil fuels for fulfilling the increasing demand for energy is polluting air (i.e. the environment),
2. LPG and CNG are considered as clean fuels but the extraction and transportation of these fuels cause environmental pollution.
3. The use of large number of sources of energy is causing global warming.

Suggestions:

1. Burning fuels must be extinguished as soon as their use is over.
2. Bulbs, tubes and other electrical appliances must be switched off as soon as you leave your room.
3. The engines of the vehicles must be switched off when these vehicles are stopped for more than a minute to save fuel.

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

Hope given NCERT Solutions for Class 10 Science Chapter 14 are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

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

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current. LearnInsta.com  provides you the Free PDF download of NCERT Solutions for Class 10 Science (Physics) Chapter 13 – Magnetic Effects of Electric Current solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 13 – Magnetic Effects of Electric Current Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Questions

In Text Questions

Question 1.
Why does a compass needle get deflected when brought near a bar magnet ?
Answer:
Compass needle is a small magnet which experiences a force in the magnetic field of a bar magnet. Due to this force, it gets deflected.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Draw magnetic field lines around a bar magnet. (CBSE 2011, 2012, 2013, 2014)
Answer:

Question 3.
List the properties of magnetic field lines. (CBSE 2015)
                                            Or
Write four properties of magnetic field lines. (CBSE (Delhi) 2010, 2011, 2012, 2013)
Answer:

1. Magnetic field lines are closed continuous curves.
2. The tangent at any point on the magnetic field line gives the direction of the magnetic field at that point.
3. No two magnetic field lines can cross each other.
4. Magnetic field lines are crowded in a region of strong magnetic field and magnetic field lines diverge in a region of weak magnetic field.

Question 4.
Why do not two magnetic field lines intersect each other ? (CBSE 2011, 2012, 2015)
                                         Or
No two magnetic field lines can intersect each other. Explain. (CBSE 2010, 2014)
Answer:
The tangent at any point on a magnetic field line gives the direction of magnetic field at that point. If two magnetic field lines cross each other, then at the point of intersection, there will be two tangents. Hence, there will be two directions of the magnetic field at the point of intersection. This is not possible. Hence, no two magnetic field lines can cross each other.

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 direction of magnetic field inside and outside the loop.
(CBSE (Delhi) 2009)
Answer:
Magnetic field inside the loop is perpendicular to the plane of table and in the downward direction. However, outside the loop, magnetic field is perpendicular to the plane of the table and in the upward direction.

Question 6.
The magnetic field in a given region is uniform. Draw a diagram to represent it.
(CBSE 2011, 2012, 2015)
Answer:

Question 7.
Choose the correct option :
The magnetic field inside a long straight solenoid carrying current is :
(a) zero
(b) decreases as we move towards its ends .
(c) increases as we move towards its ends
(d) is the same at all points.
Answer:
(b).

Question 8.
Which of the property a proton can change when it moves freely in a magnetic field ? (There may be more than one correct answer).
(a) mass
(b) speed
(c) velocity
(d) momentum.
Answer:
A force acts on a proton when it moves freely in a magnetic field. Hence its velocity and momentum can change.

Question 9.
In activity 13-7 (NCERT book), how do we think the displacement of rod AB will be affected if

1. current in rod AB is increased
2. a stronger horse shoe magnet is inserted
3. length of the rod AB is increased.

Answer:
Force acting on a current carrying conductor of length l placed perpendicular to magnetic field B is given by F = B I l

1. When I increase, F also increases. Hence the displacement of the rod increases.
2. When a stronger horse shoe magnet is inserted, magnetic field at B increases. So force also increases. Hence displacement increases.
3. When l increases, force increases and hence displacement increases.

Question 10.
A positively charged partical (alpha partical) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south
(b) towards east
(c) downward
(d) upward.
Answer:
(d).

Question 11.
State Fleming’s left hand rule with a labelled diagram. (CBSE 2005, 2010, 2011, 2012)
Answer:
Fleming’s left hand rule
Statement : Stretch the left hand such that the thumb, first finger and the central finger are mutually perpendicular to each other. If the First finger points in the direction of the magnetic Field and the Central finger points in the direction of Current, then the thumb will point in the direction of Motion (or Force) as shown in figure 24.

Thus, in Fleming’s left hand rule, first finger shows the direction of the magnetic field. The central finger shows the direction of electric current flowing in the conductor. Thumb shows the direction of force on the conductor or the direction of motion of the conductor

Question 12.
What is the principle of electric motor ? (CBSE 2012)
Answer:
Electric motor works on the principle that a current carrying conductor placed perpendicular to a magnetic field experiences a force.

Question 13.
What is the role of the split ring in an electric motor ?
Answer:
The split-ring in an electric motor reverses the direction of current in the armature coil of the motor. Therefore, the direction of the force acting on the two arms of the coil is also reversed. As a result of this, the coil of d.c. motor continues to rotate in the same direction.

Question 14.
Explain different ways to induce current in a coil. (CBSE 2010, 2011, 2012)
Answer:

1. By moving a bar magnet towards or away from the coil.
2. By placing a closed coil near another coil connected across a battery.

Question 15.
State the principle of electric generator.
Answer:
It is based on the principle of electromagnetic induction. That is, the changing magnetic field induces current in the coil.

Question 16.
Name some sources of direct current. (Bihar Board 2012, 2015)
Answer:
A dry cell, a battery, a solar cell, d.c. generator etc. are some sources of direct current.

Question 17.
Which source produces alternating current ?
Answer:
AC generator (which converts mechanical energy into alternating current or electricity) and an oscillator (a device which converts D.C. into A.C.) are the sources which produce alternating current.

Question 18.
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
(a) two revolutions
(b) one revolution
(c) half revolution
(d) one-fourth revolution,
Answer:
(c).

Question 19.
Name two safety measures commonly used in electric circuit and appliances.
(CBSE 2010, 2012, 2014, 2015)
Answer:

1. Electric fuse and
2. earthing.

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. (CBSE 2010, 2011, 2012, 2013, 2014)
Answer:
P = 2 kW = 2000 W and V = 220 V

This shows that current flowing through the oven is more than the current rating (5 A). Hence, the fuse in the circuit melts and oven is saved from damage.

Question 21.
What precautions should be taken to avoid the overloading of domestic electric circuit ? (CBSE 2010, 2011, 2012, 2015)
                                                                         Or
Write any two precautions to be taken to avoid overloading of a domestic electric circuit.
Answer:

1.  We should not connect many appliances in the same socket.
2. Electrical appliances of high power rating should not be switched on simultaneously.

NCERT Chapter End Exercises

Question 1.
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 centered on the wire.
Answer:
(d).

Question 2.
The phenomena of electromagnetic induction is
(a) the process of charging a body
(b) the process of generating magnetic field due to 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.
Answer:
(c).

Question 3.
The device used for producing electric current is called a
(a) generator
(b) galvanometer
(c) ammeter
(d) motor. (Bihar Board 2012)
Answer:
(a).

Question 4.
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 & higher voltage
(d) AC generator has slip rings while the DC generator has a commutator.
Answer:
(d).

Question 5.
At the time of short circuit, the current in the ciruit
(a) reduces substantially
(b) does not change
(c) increases heavily
(d) vary continuously. (Bihar Board 2012)
Answer:
(c).

Question 6.
State whether the following statements are true or false :
(a) an electric motor converts mechanical energy into electrical energy ‘
(b) an electric generator works on the principle of electromagnetic induction
(c) the field at the centre of a long circular coil carrying current will be parallel straight lines
(d) a wire with a green insulation is usually the live wire.
Answer:
(a) False. It converts electrical energy into mechanical energy.
(b) True.
(c) True.
(d) False. Five wire has red insulation cover.

Question 7.
List three sources of magnetic fields. (CBSE 2013)
Answer:

1. a permanent magnet
2. a current carrying conductor
3. a current carrying solenoid.

Question 8.
How does 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. (CBSE 2012, 2013)
Answer:
When electric current flows through a solenoid, magnetic field is set up around the solenoid. The pattern of the magnetic field is same as that of the magnetic field of a bar magnet. One end of the solenoid behaves as north pole and the other end of the solenoid behaves as south pole.
To determine the north and south poles of a current carrying solenoid with the help of a bar magnet, suspend it with a strong thread. Now bring the north pole of a bar magnet towards one end of the solenoid. If the solenoid attracts towards the magnet, then that face of the solenoid is south pole. If the bar magnet moves away from the solenoid, then that face of the solenoid is the north pole.

Question 9.
When is the force experienced by a current carrying conductor placed in magnetic field is the largest ?
[CBSE, (All India) 2009, 2010]
                                                                              Or
Under what condition does a current carrying conductor kept in a magnetic field experience maximum force ? (CBSE 2011, 2012, 2014, 2015)
Answer:
When current carrying conductor is placed perpendicular to the magnetic field.

Question 10.
Think 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:
Movement from electron beam from back wall to the front wall is equivalent to the flow of electric current from front wall to the back wall. The deflection of the beam means, the force is acting towards our right side. According to Fleming’s Left Hand Rule, the direction of magnetic field is vertically downward. That is, the magnetic field is perpendicular to the plane of the paper and directed inward.
Such magnetic field is shown by ⊗.

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 converts electrical energy into mechanical energy.
Principle: Electric Motor is based on the fact that a current carrying conductor placed perpendicular to the magnetic field experiences a force.

1. Armature coil: It consists of a single loop of an insulated copper wife in the form of a rectangle. Rectangle ABCD shown in figure 25 is an armature coil.
   
2. Strong field magnet: Armature coil is placed between two pole pieces (N and S poles) of a strong magnet. This magnet provides a strong magnetic field.
3. Split-ring type Commutator. It consists of two halves (R₁ and R₂) of a metallic ring. The two ends of the armature coil are connected to these two halves of the ring. Commutator reverses the direction of current in the armature coil.
4. Two carbon brushes B₁ and B₂ press against the commutator. These brushes act as the contacts between the commutator and the terminals of the battery.
5. A battery is connected across the carbon brushes. This battery supplies the current to the armature coil.

Question 12.
Name some devices in which electric motors are used.
Answer:
Electric cars, rolling mills, electric fans, hair dryers, mixers, blenders etc.

Question 13.
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is

1. pushed into the coil,
2. withdrawn from inside the coil,
3. held stationary inside the coil ?

Name the phenomenon involved in the above cases.
(CBSE 2010, Term I, 2011, 2012, 2013, 2014)

Answer:

1. When a bar magnet is pushed into the coil, induced current flows through the coil due to the phenomenon of electromagnetic induction. This induced current is indicated by the deflection of the needle of the galvanometer as shown in figure (a).
2. When a bar magnet is withdrawn from inside the coil, again induced current flows through the coil due to the phenomenon of electromagnetic induction. In this case, the direction of induced current is opposite to the direction of the current in case (i) as shown in figure (b).
3. When the bar magnet is held stationary inside the coil, there is no change in magnetic field around the coil. Hence, no induced current flows through the coil. Therefore, galvanometer shows no deflection as shown in figure (c).
   Phenomenon involved in electromagnetic induction.

Question 14.
Two circular coils A and B are placed close to each other. If the current in the coil A is changed, will some current be induced in the coil B 1 Give reason. (CBSE 2010, 2012)
Answer:
When current in coil A is changed, a changing magnetic field is set up around it. This changing magnetic field also links with coil B and hence some current will be induced in coil B due to electromagnetic induction.

Question 15.
State the rule to determine the direction of a

1. magnetic field produced around a straight conductor carrying current,
2. force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and
3. current induced in a coil due to its rotation in a magnetic field.
   (CBSE 2010, 2011, 2014)

Answer:

1. Right hand thumb rule,
2. Fleming’s left hand rule,
3. Fleming’s right hand rule.

Question 16.
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes ?
Answer:
An electric device used to convert mechanical energy (kinetic energy) into electrical energy (electricity) is called an electric generator.
Principle: Electric generator works on the principle of electromagnetic induction. When the coil of electric generator rotates in a magnetic field, induced current flows in the circuit connected with the coil.
types of electric generator

1. AC generator
2. DC generator

AC generator: AC generator converts mechanical energy into electrical energy in the form of alternating current or AC.
DC generator: DC generator converts mechanical energy into electrical energy in the form of direct current or DC.                                                AC Generator Construction : The main components of AC generator are (Figure 33) :

1. Armature : Armature coil (ABCD) consists of large number of turns of insulated copper wire wound over a soft iron core.
2. Strong field magnet : A strong permanent magnet or an electromagnet whose poles (N and S) are cylindrical in shape is a field magnet. The armature coil rotates between the pole pieces of the field magnet. The uniform magnetic field provided by the field magnet is perpendicular to the axis of rotation of the coil.
3. Slip Rings : The two ends of the armature coil are connected to two brass slip rings R₁ and R₂. These rings rotate along with the armature coil. Rings R₁ and R₂ are at different heights.
4. Brushes : Two carbon brushes (B₁ and B₂), are pressed against the slip rings. The brushes are fixed while slip rings rotate along with the” armature. These brushes are connected to the external circuit across which the output is obtained.

Working : When the armature coil ABCD rotates in the magnetic field provided by the strong field magnet, it cuts the magnetic field lines. Thus, the changing magnetic field produces induced current in the coil. The direction  of the induced current in the coil is determined by the Fleming’s right hand rule.
The current flows out through the brush B₁ in one direction in the first half of the revolution and through the brush B₂ in the next half revolution in the reverse direction. This process is repeated. Therefore, induced current produced is of alternating nature. Such a current is called alternating current.
DC generator or Dynamo Construction:

1. Armature coil. It consists of large number of turns of insulated copper wire wound on iron core in the form of a rectangle coil. Rectangle coil ABCD shown in figure 34 is an armature coil.
   
2. Strong field magnet. Armature coil is placed between two pole pieces (N and S poles) of a strong magnet. This magnet provides a strong magnetic field.
3. Split-ring Type Commutator. It consists of two halves (R₁ and R₂) of a metallic ring. The two ends of the armature coil are connected to these two halves of the ring.
4. Two carbon brushes B₁ and B₂ press against the commutator.
5. The output is shown by the glowing bulb connected across the carbon brushes.

Working of d.c. generator: When the coil of d.c. generator rotates in the magnetic field, induced potential difference is produced in the coil. This induced potential difference gives rise to the flow of current through the bulb and hence the bulb glows.
In d.c. generator, the flow of current in the circuit is in the same direction as long as the coil rotates in the magnetic field. This is because one brush is always in contact with the arm of the armature moving up and the other brush is in contact with the arm of the armature moving downward in the magnetic field.
Note: AC generator can be converted into DC generator by replacing slip rings used in AC generator by a split ring type commutator.

Question 17.
When does an electric short circuit occur ? (CBSE 2013)
Answer:
When live wire and neutral wire touch each other (i.e. come in direct contact.), the resistance of the circuit becomes small and hence large amount of current flows through it. As a result, large amount of heat is produced and the circuit catches fire.

Question 18.
What is the function of an earth wire ? Why is it necessary to earth metallic casings of electric appliances ? (CBSE 2010, 2011, 2012, 2013, 2015)
Answer:
Earth wire acts as a safety measure. When the live wire touches the metallic casing of an electric appliance, the electric current flows from the casing of the appliance to the earth through the copper wire. As the earth offers very’ low or almost no resistance to the flow of current, so large current passes through the copper wire instead of human body. This large current heats the circuit and hence the fuse in the circuit melts. As a result of this, the circuit is switched off automatically and hence the electric appliance is saved from burning and the human body suffers no electric shock.

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

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NCERT Solutions for Class 10 Science Chapter 12 Electricity

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NCERT Questions

In Text Questions

Question 1.
What does an electric circuit mean ? (CBSE 2011, 2013, 2014)
Answer:
An electric circuit is a closed conducting path containing a source of potential difference or electric energy (i.e. a cell or battery) and a device or element utilizing the electric energy.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Define the unit of current. (CBSE 2008)
Answer:
Unit of electric current is ampere. Electric current in a conductor is said to be 1 A if 1 coulomb charge flows through the cross-section of the conductor in 1 second.

Question 3.
Calculate the number of electrons consisting one coulomb of charge. (CBSE 2015)
Answer:

Question 4.
Name a device that helps to maintain a potential difference across a conductor. (CBSE 2008)
Answer:
A cell or battery.

Question 5.
What is meant by saying that a potential difference between two points is 1 V ?
[CBSE (Delhi) 2008 ; CBSE (All India) 2008, 2010 Term I]
 Or
Define the term “Volt”. (CBSE 2009, 2013)
Answer:
Potential difference between two points is 1 V if 1 joule work is done in moving 1 coulomb charge from one point to another point.

Question 6.
How much energy is given to each coulomb of charge passing through a 6 V battery ?
Answer:
Energy = Charge x Potential difference =1 C X 6 V = 6 J.

Question 7.
On what factors does the resistance of a conductor depend ? (CBSE 2009, 2011, 2012, 2013, 2014)
Answer:
Resistance of a conductor depends on

1. length (l) of the conductors,
2. area of corss-section of the conductor,
3. nature of the material of the conductor and
4. temperature of the conductor.

Question 8.
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:
Area of cross-section

therefore, resistance of thin wire is more than the resistance of thick wire. Hence, current in thick wire flows easily than in thin wire.
Let the resistance of an electrical component remains constant while the potential difference across the ends of the component decreases to half of its former value.

Question 9.
What change will occur with current through it ?
Answer:

Thus, current in the component becomes half of its former value.

Question 10.
Why are coil of electric toasters and electric irons made of an alloy rather than a pure metal ?
(CBSE 2011, 2012)
Answer:
This is because the resistivity of an alloy is more than the resistivity of a pure metal and hence more heat is produced in an alloy than in pure metal due to the flow of current. Moreover, alloy does not burn (or oxidise) easily even at higher temperature.

Question 11.
(a) Which among, iron and mercury is a better conductor ? (resistivity of iron = 10.0 x 10^-8 Ω m and resistivity of mercury = 94 x 10^-8 Ω m)
(b) Which material is the best conductor ?
Answer:
(a) A material whose resistivity is low is a good conductor of electricity. Therefore, iron is better conductor than mercury.
(b) Silver is the best conductor of electricity.

Question 12.
Draw a schematic diagram of a circuit consisting of a batteries of three of 2 V each, a 5 Ω resistor, 8 Ω resistor and a 12 Ω resistor and a plug key, all connected in series. (CBSE 2011)
Answer:

Question 13.
Redraw the circuit of question 12, putting an ammeter to measure the current through the resistor and a voltmeter to measure the potential difference across 12 Ω resistor. What would be the reading in the ammeter ?
Answer:

Question 14.
Judge the equivalent resistance when the following are connected in parallel :
(a) 1 Ω and 10⁶ Ω
(b) 1 Ω and 10³ Ω and 10⁶ Ω.
(CBSE 2013)
Answer:
(a) When resistors are connected in parallel, then equivalent resistance of the combination is less than the least resistance in the combination. Therefore, equivalent resistance of 1 Ω and 10⁶ Ω connected in parallel is approximately 1 Ω but less than 1 Ω.
(b) The equivalent resistance is approximately 1 Ω but less than 1 Ω.

Question 15.
An electric lamp of 100 W, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to 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 ?
Answer:

Question 16.
What is
(a) highest
(b) lowest resistance that can be secured by combining four coils of resistances 4 Ω, 8 Ω, 12 Ω, 24 Ω ? (CBSE 2010 Term I, 2012, 2013)
Answer:

Question 17.
Why does the connecting cord of an electric heater not glow while the heating element does ? [CBSE (Delhi) 2008, 2010, 2011, 2013]
Answer:
This is because resistance of cord of electric heater is less than the resistance of heating element. So more heat is produced in the heating element and less heat is produced in the cord. Due to more heat, heating element glows.

Question 18.
Compute the heat generated while transferring 96000 coulomb of charge in one hour through a potential difference of 50 V. (CBSE 2012, 2013)
Answer:

Question 19.
An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 seconds. (CBSE 2010)
Answer:

Question 20.
What are the advantages of connecting electrical devices in parallel with a battery instead of connecting them in series ?
                                                                           Or
Give two advantages of connecting electrical devices in parallel with battery. (CBSE 2010 Term I)
                                                                           Or
In a house-hold electric circuit different appliances are connected in parallel to one another. Give two reasons. (CBSE Sample Papers, CBSE 2012)
                                                                          Or
Why is parallel arrangement used in domestic ? (NCERT Question Bank, CBSE 2015)
Answer:

1. If any one of the electric devices in parallel fuses, then the working of other devices will not be affected.
2. When different devices are connected in parallel, they draw the current as per their requirement and hence they work properly.

Question 21.
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 ? (CBSE 2012)
Answer:
(a) We get 4 Ω resistance if 3 Ω and 6 Ω resistors are connected in parallel and this parallel combination is . connected in series with 2 Ω as shown in figure.

Question 22.
What determines the rate at which energy is delivered by an electric current ? [CBSE (All India) 2008]
Answer:
Electric power determines the rate at which energy is delivered by an electric current.

Question 23.
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and energy consumed in 2 h.
[CBSE (All India) 2008]
Answer:
Power, P = VI = 220 x 5 = 1100 W
Energy consumed = Power x Time
= 1100 W x 2 h = 2200 Wh = 2.2 kWh.

NCERT Chapter End Exercises

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) 1/25
(b) 1/5
(c) 5
(d) 25
Answer:

∴ (d) is correct answer.

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) is correct answer.

Question 3.
An electric bulb is rated as 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) is the correct answer.

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 an electric circuit. 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) is the correct answer.

Question 5.
How is voltmeter connected in circuit to measure the potential difference between two points ? (CBSE 2011, 2012)
Answer:

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 diameter is doubled ?
Answer:

When D is doubled and length remains the same, resistance becomes 1/4 th of the original resistance.

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 :

Plot a graph between V and I and calculate the resistance of that resistor. (CBSE Sample Paper 2017-18)
Answer:

Question 8.
When a 12 V battery is connected across an unknown resistance, there is a current of 2.5 mA in the circuit. Find the value of resistance of the resistor.
Answer:

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 12 Ω resistor ? (CBSE 2010 Term I)
Answer:

Question 10.
How many 176  Ω resistors (in parallel) are required to carry 5 A on 220 V line ?
Answer:

Practical Skills Based Questions (Two Marks Questions)

Question 1.
In,a voltmeter, there are 20 divisions between the 0 mark and 0.5 mark. Calculate the least count of the voltmeter.
(CBSE 2015)
Answer:
Least count of voltmeter= value of 1 division
Here, 20 divisions = 0.5 V

Thus, least count of voltmeter = 0.025 V.

Question 2.
To verify Ohm’s law in the laboratory. Name the following circuit components used. (CBSE 2015)

Answer:
(a) Variable resistance
(b) Battery
(c) Wire crossing without joining
(d) Rheostat or adjustable resistance.

Question 3.
A student prepared a circuit diagram to study the dependence of potential difference (V) on electric current (I) across a resistor.

In this circuit diagram X, Y, Z, P are represented for the components.
(a) X = ……………..
(b) Y = ……………..
(c) Z = ………………
(d) P = ………………
(CBSE 2015)
Answer:
X = Ammeter
Y = Resistor
Z = Voltmeter
P = Battery.

Question 4.
Least count of a voltmeter and an ammeter in given figures would respectively be : (CBSE 2015)

Answer:
Least count of a voltmeter or an ammeter is equal to the value of 1 division on the scale.
In a voltmeter, 5 divisions = IV
or 1 division = 1/5 V = 0.2 V
Thus, least count of voltmeter = 0.2 mA
In an ammeter, 5 division = 1 mA
or 1 division = 1/5 mA = 0.2 mA
Thus, least count of ammeter = 0.2 mA.

Question 5.
To verify Ohm’s law, a student drew a circuit diagram which is given below :

1. Name two components in this circuit diagram which are connected in series.
2. Name two components in this circuit diagram which are connected in parallel. (C. B. S. E. 2015)

Answer:

1. Key, rhoestat, battery, ammeter and resistor are connected in series.
2. Resistor of resistance R and voltmeter (V) are connected in parallel.

Question 6.
In the Ohm’s law experiment, it is advised to take out the key from the plug when the observations are not being taken. Why it is essential l (CBSE 2015)
Answer:
Ohm’s law is valid only if the resistance of a resistor remains constant ‘during the experiment. If the key from the plug is not taken out when the observations are not taken, then the resistance of the resistor increases due to heat produced as a result of continuous flow of current through it. Hence, Ohm’s law cannot be verified.

Question 7.
The rest positions of the pointers of a milliammeter and volt-meter not in use are as shown in fig. A. When a student uses these in his experiment, the reading of pointers are in positions shown in fig. B.

Calculate the corrected value of current and voltage in this experiment.  (CBSE 2015)
Answer:
Least count of milliammeter = 10mA/5 = 2 mA
Least count of voltmeter = 1V/5 = 0.2 V
Zero error of milliammeter = 2 x 2 mA = 4 mA
Zero error of voltmeter = 3 x 0.2 V = 0.6 V
Correct value of current = 38 mA + 4 mA = 42 mA
Correct value of voltmeter = 3.6V – 0.6 V = 3.0 V.

Question 8.
In an experiment to study the dependence of current on potential difference across a resistor, a student obtained a graph as shown

Calculate the value of resistance of the resistor. (CBSE 2015)
Answer:

Question 9.
In a given ammeter, a student sees that needle indicates 17 divisions in ammeter while performing an experiment to verify Ohm’s law. If ammeter has 10 divisions between 0 and 0.5 A, then what is the value corresponding to 17 divisions ?  (CBSE Sample Paper 2017-18)
Answer:
10 Div = 0.5 A
1 Div = 0.5 A/10 = 0.05 A
∴ 17 Div = 0.05 A x 17 = 0.85 A

Question 10.
While performing an experiment to verify Ohm’s law, what precautions are to be taken ?
Answer:

1. Connections should be tight.
2. The conductor used should be such that its resistance does not change much with increase in temperature.
3. The plug of the key must only be inserted while reading ammeter and voltmeter. There after, the plug of the key must be taken out to avoid heating of conductor with the continuous flow of current through it.

Question 11.
In a given voltmeter, a student sees that the needle indicates 12 divisions in voltmeter while performing an experiment to verify Ohm s law. If voltmeter has 10 divisions between 0 and 1.0 V, then what is the value corresponding to 12 divisions ?
Answer:

Question 12.
The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below :

Plot a graph between V and I and calculate the resistance of the resistor. (CBSE Sample Paper 2017-18)
Answer:
Scale : Along x-axis, 1 div = 0.1 V
Along y-axis, 1 div = 0.1 A
Graph between V and I is shown in figure:

Question 13.
An ammeter has a range of 0—3 ampere and there are 30 divisions on the scale. Calculate the least count of the ammeter. (CBSE 2015)
Answer:
30 divisions = 3 A
1 division = 3 A/30 = 0.1 A
Thus, least count of ammeter = 0.1 A

NCERT Solutions for Class 10 Science Chapter 12 Electricity

Hope given NCERT Solutions for Class 10 Science Chapter 12 are helpful to complete your science homework.

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