Class 10 Science Chapter 14 Source of Energy answer to each chapter is provided in the list so that you can easily browse throughout different chapters NCERT Class 10 Science Chapter 14 Source of Energy and select need one.
Class 10 Science Chapter 14 Source of Energy
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Source of Energy
Chapter – 14
Textual Questions and Answers:
Page – 243
Q.1. What is a good source of energy?
Ans: A good source of energy would be one:
1. It produces a lot of heat per unit mass.
2. It does a huge amount of work per unit mass.
3. It is easily accessible.
4. It is easy to store and transport.
5. It is economical.
6. It produces less amount of smoke.
Q.2. What is a good fuel?
Ans: A good fuel:
(a) Good fuel is found in nature which makes it easily available.
(b) Its calorific value should be large.
(c) It burns very efficiently without forming residues and has a high C.V (calorific value).
(d) It should produce no smoke and should not leave any residence.
(e) It is very cheap at the economic level and is eco-friendly.
(f) It should burn at controllable rate.
Q.3. If you could use any source of energy for cooking your food, which one would you use and why?
Ans: We would prefer to use L.P.G. or Gobar gas. Because these gases have high calorific value, not produce pollution, easily available and is economical.
Page – 248
Q.1. What are disadvantages of fossil fuels?
Ans: Disadvantages of fossil fuels are:
(i) Air pollution.
(ii) The oxides of carbon, nitrogen, and sulphur that are released on burning fossil fuels are acidic oxides.
These lead to acid rain which affects our water and soil resources
(iii) Global warming- the greenhouse effect of gases like carbon dioxide.
(iv) The fossil fuels are non-renewable sources of energy.
Q.2. Why are we looking at alternative sources of energy?
Ans: The main reason why we are searching for an alternate source of energy is because fossil fuels are non-renewable sources of energy which means they are not available in abundant quantities and cannot be replenished. Fossil fuels will continue to get exhausted if their consumption is not controlled. Therefore, it is far better to switch to alternate sources of energy in order to apply the concept of sustainable development.
Geothermal energy is the energy which is obtained from the earth. This energy can be obtained from the hot spots that are formed when the molten rocks present at the core of the earth are pushed towards the earth’s crust. Hot springs are commonly used for the production of electricity in the geothermal power plants.
Q.3. How has the traditional use of wind and water energy been modified for our convenience?
Ans: Earlier, the windmills were used to harness wind energy to do mechanical work such as lifting/drawing water from a well. Today, windmills are used to generate electricity.In windmills, the kinetic energy of wind is harnessed and converted into electricity.
Water energy which was used for transportation before is now a good source to generate electricity. Dams has been constructed on river for generating electricity. Waterfalls were used as a source of potential energy which was converted to electricity with the help of turbines.
Page – 253
Q.1. What kind of mirror-concave, convex or plane mirror would be best suited for use in a solar cooker? Why?
Ans: A concave mirror reflector would be best suited for use in a solar cooker. This is because a concave mirror is a converging mirror which converges all the light falling on it. It converges a large amount of sun’s heat rays onto the required area of cooking holder. A plane mirror does not converge all the light therefore, concave is used. And convex mirror reflector is a diverging mirror so it is also not used.
Q.2. What are the limitations of the energy that can be obtained from the oceans?
Ans: The following are some of the limitations of ocean energy:
1. The tidal energy is affected by the relative positions of the earth, the sun, and the moon.
2. High dams are required for converting tidal energy into power.
3. Strong waves are necessary to generate electricity from wave energy.
4. A temperature difference of more than 20°C between hot surface water and cool water at depth is required to store ocean thermal energy.
Q.3. What is geothermal energy?
Ans: Geothermal energy is heat that is produced inside the Earth. (Geo signifies “earth,” and thermal signifies “heat” in Greek.) It is a sustainable asset that can be gathered for human use. Around 2,900 kilometers (1,800 miles) beneath the Earth’s hull, or surface, is the most sultry piece of our planet: the center.
Q.4. What are the advantages of nuclear energy?
Ans: Nuclear energy is preferred to fossil energy, hydro energy, thermal energy etc for the following reasons.
(a) One of the most low-carbon energy sources.
(b) It also has one of the smallest carbon footprints.
(c) It’s one of the answers to the energy gap.
(d) It’s essential to our response to climate change and greenhouse gas emissions.
(e) Reliable and cost-effective.
Page – 253
Q.1. Can any source of energy be pollution free? Why or why not?
Ans: No source of energy can be called pollution-free, because, the use of any source of energy disturbs the environment in one way or the other. A source of energy like a solar cell is pollution free in actual operation but the assembly of the device might have caused some damage to the environment. So, in absolute sense, no source of energy can be called pollution free.
Q.2. Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Ans: Hydrogen is a 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 heating of the environment in the long run.
Some of the environment consequence of the increasing demand for energy are the following:
(a) The combustion of fossil is producing acid rain and damaging plants (crops), soil and aquatic life.
(b) The burning of fossil is increasing the amount of greenhouse gas carbon dioxide in the atmosphere.
(c) The cutting down of trees from the forest (deforestation) for obtaining fir-wood is causing soil erosion and destroying wild life.
(d) The construction of the hydro-power plants is disturbing ecological balance.
(e) Nuclear power plants are increasing radioactivity in the environment.
The various factors which we should keep in mind while choosing a sources of energy are:
(a) The ease of extracting energy from that source
(b) The cost of extracting energy from the sources
(c) The efficiency of technology available to extract energy from that sources.
(d) The damage to environment which will be caused by using that sources.
Page – 254
Q.1. Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Ans: Hydro-Energy and Biomass energy are the renewable sources of energy:
(a) Hydro-Energy is the energy produced by fast flowing water. It is a renewable source of energy because it is supplied by the water cycle in nature and it will never get exhausted.
(b) The energy derived from flowing water, wind, sun and ocean are renewable sources because these sources can be harmless into energy so long as the present solar system exists.
Q.2. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choice.
Ans: Two exhaustible energy sources are as follows:
(a) Coal: It is produced from dead remains of plants and animals that remain buried under the earth’s crust for millions of years. It takes millions of years to produce coal. Industrialization has increased the demand of coal. However, coal cannot replenish within a short period of time. Hence, it is a non-renewable or exhaustible source of energy.
(b) Wood: It is obtained from forests. Deforestation at a faster rate has caused a reduction in the number of forests on the Earth. It takes hundreds of years to grow a forest. If deforestation is continued at this rate, then there would be no wood left on the Earth. Hence, wood is an exhaustible source of energy.
EXERCISES:
Q.1. A solar water heater can not be used to get hot water
(a) A sunny day.
(b) A cloudy day.
(c) A hot day.
(d) A windy day.
Ans: (b) A cloudy day.
Q.2. In Which of the following is not an example of a biomass energy source?
(a) Wood.
(b) Gobar-gas.
(c) Nuclear energy.
(d) Coal.
Ans: (c) Nuclear energy.
Q.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.
Ans: (c) Nuclear energy.
Q.4. Compare and contrast fossil fuels and the Sun as direct sources of energy.
Ans: Similarity:
(a) Both are natural sources of energy.
(b) Both are widely used sources of energy.
Contrast:
(a) Fossil fuels are non-renewable. But the energy of Sun in renewable.
(b) Fossil fuels causes lot of air pollution. But the energy of Sun pollution free.
Q.5. Compare and contrast biomass and hydro electricity as sources of energy.
Ans: (a) Biomass is a renewable source of energy and hydroelectricity is also a renewable source of energy.
(b) The use of biomass by burning causes air pollution but the use of hydroelectricity does not cause any pollution.
(c) Biomass energy can be obtained without using any special device but hydroelectricity can be produced only by establishing hydro-power plants.
Q.6. What ar the limitations of extracting energy from
(a) The wind?
Ans: Limitations of wind energy:
(i) Need a large open space to couple a number of wind mills.
(ii) It is not available everywhere and at all the times.
(iii) Wind velocity must be sufficient.
(b) Waves?
Ans: Limitations of extracting energy from waves:
(i) Wave energy is viable proposition only when and where the waves are very strong. This has constraints of time and location.
(c) Tides?
Ans: Limitation of tidal energy:
(i) Its cost is huge and is not possible to build such dams everywhere.
(ii) Huge amount of silt gets deposited on basins in the dams.
Q.7. On what basis would you classify energy sources as:
(a) Renewable and non-renewable?
Ans: The energy sources that can be regenerated are called renewable sources of energy.
Renewable energy:
(a) A renewable source of energy is one that replaces itself in the natural world.
(b) They include the sun, wind, water that is moving, biomass, etc.
(c) The energy is derived from resources that can be regenerated naturally over time and are therefore considered to be renewable.
(d) Despite the fact that the majority of renewable energy sources are sustainable, some are not.
Non-renewable energy:
(a) Non-renewable energy sources are those that will run out of energy after a few hundred years.
(b) The sources of energy that are non-renewable include coal, petroleum, etc.
(c) The majority of the world’s energy comes from non-renewable resources like coal and oil, which are used to run companies, houses, and automobiles.
(d) Renewable resources can naturally regenerate themselves, whereas nonrenewable resources cannot, which is how these two types of resources vary from one another.
(b) Exhaustible and inexhaustible?
Ans: Exhaustible sources are those energy sources which deplete and exhaust after a few hundred years.
Q.8. What are the qualities of an ideal sources of energy?
Ans: Am ideal source of energy:
(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.
Q.9. What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Ans: Solar energy is used in the solar cookers to cook food. As solar energy is renewable source of energy and it is available in unlimited amount, the operation cost of solar cooker is very low. But the manufacturing cost of solar cooker is very high and it doesn’t work in absence of sunlight. Places where there is not enough sunlight as the days are too short or always cloudy, solar cookers cannot be used.
Q.10. What are the environmental consequences of the increasing demand for energy? What steps suggest to reduce energy consumption?
Ans: The demand of energy is increasing day by day. Exploiting any would no. source of energy may disturb the environment in one way or other. For example getting energy from fossil fuel may cause lot of pollution in air.
Steps for reducing energy consumption:
(i) Burning of fossil fuels to meet increasing demand for energy causes air-pollution.
(ii) Construction of dams on rivers to generate hydro-electricity destroys large ecosystems which get submerged under water in the dams. Large amounts of methane (which is a greenhouse gas) is produced when submerged vegetation rots under anaerobic conditions.
In order to reduce energy consumption:
(i) Fossil fuels should be used with caution to get their maximum benefit
(ii) Energy efficient devices such as pressure cookers, compact fluorescent lamps (CFLs), etc. should be used
(iii) The devices/machines used for energy conversion should be maintained or repaired regularly in order to keep them efficient
(iv) We should use electricity or any other source of energy judiciously as ‘energy saved is energy produced’.
Multiple Choice Questions:
Q.1. Which one of the following is not a source of energy?
(a) Levers.
(b) Muscle power.
(c) Water stored at dams.
(d) Flowing water.
Ans: (a) Levers.
Q.2. The process of burning fuel is called
(a) Respiration.
(b) Oxidation.
(c) Explosion.
(d) Combustion.
Ans: (d) Combustion.
Q.3. Which gas cannot used as a fuel?
(a) C.N.G.
(b) L.P.G.
(c) Oxygen.
(d) Hydrogen.
Ans: (c) Oxygen.
Q.4. Infra-red rays are
(a) Harmful to skin.
(b) Bright red in colour.
(c) Having more energy than ultraviolet rays.
(d) Having less energy as compared to ultraviolet rays.
Ans: (d) Having less energy as compared to ultraviolet rays.
Q.5. Natural gas is mostly
(a) Oxygen.
(b) Hydrogen.
(c) Ammonia.
(d) Methane.
Ans: (d) Méthane.
Q.6. Which of the following is an example of biomass energy source?
(a) Ocean energy.
(b) Tidal energy.
(c) Atomic energy.
(d) Gobar energy.
Ans: (d) Gobar energy.
Q.7. The device which converts solar energy into electrical energy is
(a) Solar cooker.
(b) Solar geyser.
(c) Solar cell.
(d) All the above.
Ans: (c) solar cell.
Q.8. In a nuclear reactor, liquid sodium metal is used as:
(a) Fuel.
(b) Coolant.
(c) Moderator.
(d) None of these.
Ans: (b) Coolant.
Q.9. Unit of calorific value of a substance is
(a) Kcal.
(b) Calorie.
(c) Jkg.
(d) Jkg⁻¹
Ans: (d) J Kg⁻¹
Q.10. Which of the following causes maximum pollution on burning?
(a) Gobar cakes.
(b) Petrol.
(c) C.N.G.
(d) L.P.G.
Ans: (a) Gobar cakes.
Q.11. Which of the following is a nonrenewable source of energy?
(a) Wood.
(b) Sun.
(c) Fossil fuels.
(d) Wind.
Ans: (c) Fossil fuels.
Q.12. Fuel used in thermal power plants is
(a) Water.
(b) Uranium.
(c) Biomass.
(d) Fossil fuel.
Ans: (d) Fossil fuel.
Q.13. Which of the following is not a green house gas?
(a) CO₂
(b) CH₄
(c) SO₂
(d) CO
Ans: (d) CO.
Q.14. The energy is obtained by nuclear fusion process in
(a) The sun.
(b) Nuclear reactor.
(c) Atomic bomb.
(d) Geosystem.
Ans: (a) The sun.
Q.15. Which is not a good source of energy?
(a) It is easy to store.
(b) It gives tremendous amount of energy.
(c) It burns easily.
(d) It produces no pollution.
Ans: ( b ) It gives tremendous amount of energy.
Q.16. Which is the ultimate source of energy?
(a) Water.
(b) Sun.
(c) Uranium.
(d) Fossil fuels.
Ans: ( b ) Sun.
Q.17. Choose the correct statement:
(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.
Ans: (a) Sun can be taken as an inexhaustible source of energy.
Q.18. Gobar gas is-
(a) Foul smelling gas.
(b) Sweet smelling gas.
(c) Having high calorific value.
(d) Useless.
Ans: (c) Having high calorific value.
Q.19. A turbine can not be rotated by
(a) Flowing water.
(b) Heat of sun.
(c) Steam.
(d) Moving win.
Ans: (b) Heat of sun.
Q.20. Which of the following substances can be used to construct a solar cell?
(a) Silicon.
(b) Arsenic.
(c) Silver.
(d) Platinumele.
Ans: (a) Silicon.
Q.21. What are the limitation of using solar energy?
Ans: Limitations of Solar Energy:
- Can be harnessed only at those places which get plenty of sunlight.
- Cannot be harnessed beyond certain latitudes.
- Cannot be harnessed during night.
- Current technologies are very costly.
Q.22. What is see wave energy? How is it obtained?
Ans: You may have noticed that there is a certain kind of air force when you go near any seashore. This is due to a type of energy that gets transport by wind waves. This energy is also known as wave power.
Sea wave tidal energy is harnessed in three ways:
(i) Wave surge or focussing devices: These shoreline devices, also called “tapered channel” or “tapchan” systems, rely on a shore-mounted structure to channel and concentrate the waves, driving them into an elevated reservoir.
(ii) Pitching or Floats devices rise of fall with rising and falling waves. They are connected to a shaft by some mechanical arrangement to produce electricity.
(iii) Oscillating column water are pneumatic devices using up and down motion to compress and decompress air. The rising and falling water devices air into or out of the top of cylindrical shaft powering an air driven turbine.
Q.23. State whether the statements are true or false.
(i) Gobar gas emits foul smell.
Ans: False.
(ii) Black surface are good absorber of heat.
Ans: True.
(iii) Solar cells convert solar energy into electric energy.
Ans: True.
(iv) Ozone layer prevents infrared rays from entering earth’s atmosphere.
Ans: False.
Q.24. What part of solar energy is harmful to us?
Ans: Ultraviolet rays. These cause skin cancer.
Q.25. What is solar energy?
Ans: Solar energy is created by nuclear fusion that takes place in the sun.
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