NCERT Solutions for Class 10th Science
Chapter 14 – SOURCES OF ENERGY
(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)
Q.1 What is a good source of energy?
Ans A good source of energy would be one with the following characteristics:
1) It should be economical.
2) It should be easily accessible.
3) It should have high efficiency i.e. it should perform a large amount of work per unit volume or mass.
4) It should be easy to store and transport.
5) It should be clean and renewable.
Q.2 What is a good fuel?
Ans 1) It should be economical.
2) It should be easily accessible.
3) It should have high calorific value.
4) It should be easy to store and transport.
5) It should be environment friendly and produces less amount of smoke.
Q.3 If you could use any source of energy for heating your food, which one would you use and why?
Ans Liquified petroleum gas (LPG) can be used for cooking and heating food because:
1) It is a clean fuel
2) It is easy to store and transport
3) It has high calorific value
4) It is easily accessible.
Q.4 What are the disadvantages of fossil fuels?
Q.5 Why are we looking at alternate sources of energy?
Q.6 How has the traditional use of wind and water energy been modified for our convenience?
Q.7 What kind of mirror concave, convex or plain would be best suited for use in a solar cooker? Why?
Q.8 What are the limitations of the energy that can be obtained from the oceans?
Ans Energy that can be obtained from the oceans i.e. tidal energy, wave energy and ocean thermal energy has certain limitations:
1) Tidal energy: Tidal energy (due to gravitational pull of mainly moon on earth) is harnessed by constructing a dam across a narrow opening to the sea but such locations are limited.
2) Wave energy: Wave energy (due to strong wind across sea) would be a viable proposition only where waves are very strong.
3) Ocean thermal energy: Ocean thermal energy (due to uneven heating in depth of water by sun) can be harnessed only if the temperature difference between the water at the surface and water at depths up to 2 km is 20 K (20°C) or more.
In other words, we can say that the energy potential from the sea (tidal energy, wave energy and ocean thermal energy) is quite large, but efficient commercial exploitation is difficult.
Q.9 What is geothermal energy?
Q.10 What are the advantages of nuclear energy?
Q.11 Can any source of energy be pollution-free? Why or why not?
Ans Source of energy can be pollution-free like solar energy but the methods used to harness these energies cause damage to the environment in one way or the other. For example,
1) Solar cell which uses solar energy causes environment damage during its assembly and installation.
2) Dams constructed to harness hydel energy cause a lot of damage to the biodiversity.
3) Leakages in case of nuclear energy can cause serious damage to the environment.
Q.12 Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Q.13 Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Q.14 Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
EXERCISES
Q.1 A solar water heater cannot be used to get hot water on
(a) a sunny day. (b) a cloudy day.
(c) a hot day. (d) a windy day.
Ans (b) a cloudy day.
Q.2 Which of the following is not an example of a bio-mass 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) bio-mass.
Ans (c) nuclear energy
Q.4 Compare and contrast fossil fuels and the Sun as direct sources of energy.
Q.5 Compare and contrast bio-mass and hydro electricity as sources of energy.
Q.6 What are the limitations of extracting energy from
(a) the wind? (b) waves? (c) tides?
Q.7 On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?
Q.8 What are the qualities of an ideal source of energy?
Q.9 What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Q.10 What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Ans The increasing demand for energy due to industrialisation and various activities can only be met through energy sources like fossil fuels, hydel energy, solar energy, wind energy etc. But this will have an adverse impact on the environment and following consequences happen:
1) Burning of fossil fuels like coal and petroleum products for meeting the demands causes air pollution, acid rain and global warming.
2) Solar cell which uses solar energy causes environment damage during its assembly and installation.
3) Dams constructed to harness hydel energy cause a lot of damage to the biodiversity.
In other words we can say that, any source of energy disturbs the environment in some way or the other. Hence we should take some measures to reduce energy consumption and utilise it judiciously to preserve our environment.
Steps to reduce energy consumption:
1) Save electricity by switching off unnecessary electrical appliances like fan etc.
2) We should use fuel like petrol, diesel carefully and prefer public transport.
3) Energy efficient appliances should be used like using CFL or LED lamps instead of bulbs to conserve energy.