April 10, 2026
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Chapter 14: Sources of Energy
Complete NCERT Solutions (Intext + Exercise) | CBSE Class 10 Science | Questions & Marks
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Class 10 (CBSE) - SYLLABUS
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Intext Questions (Page 248)
12 marks
What is a good source of energy?
Answer: A good source of energy is one that: (i) does a large amount of work per unit mass/volume, (ii) is easily accessible, (iii) is easy to store and transport, (iv) is economical, and (v) causes less pollution.
22 marks
What is a good fuel?
Answer: A good fuel has high calorific value, burns without smoke, leaves minimal ash, is easy to ignite, cheap, and easily available.
32 marks
If you could use any source of energy for heating your food, which one would you use and why?
Answer: Solar energy – renewable, pollution-free, and freely available in sunny regions. Alternatively, LPG for convenience.
Intext Questions (Page 253)
42 marks
What are the disadvantages of fossil fuels?
Answer: (i) They are non-renewable and will exhaust. (ii) Burning releases CO₂, causing global warming. (iii) Produces pollutants like SO₂ and NO₂ causing acid rain. (iv) Mining causes environmental damage.
52 marks
Why are we looking at alternate sources of energy?
Answer: Fossil fuels are limited, polluting, and their combustion contributes to climate change. Alternate sources are renewable and cleaner.
62 marks
How has the traditional use of wind and water energy been modified for our convenience?
Answer: Wind energy used in windmills to generate electricity. Water energy used in hydroelectric power plants by building dams to convert potential energy to electricity.
Intext Questions (Page 256)
72 marks
What kind of mirror – concave, convex or plain – would be best suited to be used in a solar cooker? Why?
Answer: Concave mirror – it converges sunlight to a point (focus), producing high temperature required for cooking.
82 marks
What are the limitations of the energy that can be obtained from the oceans?
Answer: (i) High cost of setup, (ii) limited locations with suitable tidal range, (iii) variable energy output, (iv) potential harm to marine ecosystems.
92 marks
What is geothermal energy?
Answer: Geothermal energy is the heat energy from within the earth's crust, produced by radioactive decay. It can be used to generate electricity in geothermal power plants.
102 marks
What are the advantages of nuclear energy?
Answer: (i) High energy density (large amount from small fuel). (ii) No CO₂ emission during operation. (iii) Reliable base load power.
NCERT Exercise Questions (Page 256)
Ex 11 mark
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 (insufficient sunlight).
Ex 21 mark
Which of the following is not an example of a bio-mass energy source? (a) wood (b) gobar gas (c) nuclear energy (d) coal.
Answer: (c) nuclear energy.
Ex 31 mark
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) fossil fuels (d) biomass.
Answer: (a) geothermal energy (comes from Earth's interior, not Sun).
Ex 42 marks
Compare and contrast fossil fuels and the Sun as direct sources of energy.
Answer: Fossil fuels are non-renewable, cause pollution, and are stored solar energy. The Sun is a renewable, clean, direct source. Fossil fuels are convenient but exhaustible.
Ex 53 marks
What are the limitations of extracting energy from (a) the wind (b) waves (c) tides?
Answer: (a) Wind: intermittent, requires large land area, not feasible everywhere. (b) Waves: high cost, limited locations, variable intensity. (c) Tides: only few locations with high tidal range, seasonal variations.
Ex 62 marks
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: Renewable: can be replenished naturally (solar, wind). Non-renewable: finite (fossil fuels). Exhaustible = non-renewable; inexhaustible = renewable. They are essentially the same classification.
Ex 73 marks
What are the qualities of an ideal source of energy?
Answer: High energy output per unit mass, renewable, pollution-free, easy to store/transport, economical, safe, and universally available.
Ex 83 marks
What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Answer: Advantages: no fuel cost, pollution-free, retains nutrients. Disadvantages: slow cooking, weather-dependent, cannot be used at night. Limited utility in cloudy/rainy regions or high latitudes.
Ex 92 marks
What are the environmental consequences of using fossil fuels? Suggest steps to minimise the pollution caused by them.
Answer: Consequences: air pollution (SO₂, NO₂, CO), global warming (CO₂), acid rain. Steps: use cleaner fuels (CNG), improve combustion efficiency, use catalytic converters, promote public transport, shift to renewables.
Ex 102 marks
Why is there a need to harness non-conventional sources of energy? Give two main reasons.
Answer: (i) Fossil fuels are depleting fast. (ii) Conventional sources cause pollution and global warming. Non-conventional sources are renewable and cleaner.
Ex 112 marks
How can biogas solve the energy problem mainly in rural India? Give your suggestion.
Answer: Biogas from cattle dung provides clean fuel for cooking and lighting, reduces deforestation, and supplies enriched manure. It is cost-effective for rural households.
Additional Important Questions
A12 marks
What is a hydroelectric power plant? Mention one advantage and one disadvantage.
Answer: It converts potential energy of stored water into electricity. Advantage: renewable, no fuel cost. Disadvantage: large land submergence, displacement of people.
A22 marks
What is nuclear fission? Give an example.
Answer: Splitting of a heavy nucleus into lighter nuclei with release of energy. Example: Uranium-235 absorbs neutron and splits.
NCERT Class 10 Science | Chapter 14: Sources of Energy | Font: Lato 14px | Complete solutions with page numbers (248, 253, 256).
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