Class 10 Science

Sources of Energy

NCERT Solution

Question 1: A solar water heater cannot be used to get hot water on

  1. A sunny day
  2. A cloudy day
  3. A hot day
  4. A windy day

    Answer: (b) A cloudy day

Question 2: Which of the following is not an example of a bio-mass energy source?

  1. Wood
  2. Gobar-gas
  3. Nuclear energy
  4. Coal

    Answer: (c) Nuclear energy

Question 3: Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Sun’s energy?

  1. Geothermal energy
  2. Wind energy
  3. Nuclear energy
  4. Bio-mass

    Answer: (c) Nuclear Energy

Question 4: Compare and contrast fossil fuels and the Sun as direct sources of energy.

Answer: Sun is the direct source of energy, while fossil fuels are formed because of the solar energy stored in them. When green plants prepare food, they convert the solar energy into chemical energy which is stored in the form of biomass. The same biomass gets transferred to the animals. Thus, the energy in the form of biomass which is stored in fossil fuels has come from the sun.

Question 5: Compare and contrast bio-mass and hydroelectricity as sources of energy.

Answer: Biomass and hydroelectricity are different in many aspects. Hydroelectricity is generated using the kinetic energy from moving water, while the energy from biomass is generated by decomposition of farm waste. Since biomass is composed of organic compounds so energy from biomass results in air pollution. Hydroelectricity, on the other hand, is pollution free.

Question 6: What are the limitations of extracting energy from:

  1. Wind

    Answer: Large tract of land is required for establishment of wind farms. They can be established only at those places where wind speed is high enough. Initial cost of establishing a wind farm is very high and the cost of maintenance is also high.
  2. Waves

    Answer: Energy from waves can be harnessed only at selected places, only in coastal areas.
  3. Tides

    Answer: Energy from tides can be harnessed only at selected places, only in coastal areas. Technologies for harnessing energy from waves and tides are still at experimental stage and hence are less efficient and very costly.

Question 7: On what basis would you classify energy sources as:

  1. Renewable and non-renewable
  2. Exhaustible and inexhaustible

Are the options given in (a) and (b) are the same?

Answer: Options given in (a) and (b) are almost same. An energy source which can be quickly renewed is called renewable or inexhaustible. On the other hand, the energy source which cannot be renewed in foreseeable future are called non-renewable or exhaustible.

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

Answer: Characteristics of an ideal source of energy:

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

Answer: Advantages of Solar Cooker:

Disadvantages of Solar Cooker:

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

Answer: Environmental consequences of increasing demand for energy are as follows:

Steps to reduce energy consumption: