0
1. (b) cloudy day.

2. (c) nuclear energy

3. (c) nuclear energy

4. Distinction between fossils fuels and Sun energy:

Fossils fuel
Sun energy
i. These are non-renewable and
exhaustible sources of energy.
ii. Combination of these causes
pollution.
iii. Fossil fuels are costly but
energy can be obtained easily.
i. Sun is a renewable and
inexhaustible source of energy.
ii. It does not cause pollution or
degradation of environment.
iii. It is freely available but
devices used to harness it are
costly.


5. Difference between bio-mass and hydro electricity:

Bio-mass energy
Hydro energy
i. Bio-gas plant is cheap, small in
size and can be installed
anywhere.
ii. These utilize wastes bio-mass
materials like cow dung, plant
residue, vegetable waste and
sewage etc.
i. It can be generated only at few
places in hilly terrain by
constructing dam over river.
ii. These utilize kinetic energy of
flowing water or potential
energy of water stored at a
height.


6. Limitation of extracting energy from the wind:
i. It can be established at those places only, where wind blows for the greater
part of a year.
ii. Wind speed should be higher than 15 km/h.
iii. It requires high level of maintenance.
Limitation of extracting wave energy and tidal energy:
i. It can be harnessed by trapping the sea waves in a dam. Only very few
suitable sites exist where dams can be constructed.
ii. It is not a continuous and reliable source of energy.
iii. it is extremely costly and difficult to use.

7. (a) Renewable sources of energy are those sources which can be regenerated
again. Non-renewable sources of energy are those sources which would get
depleted some day and cannot be regenerated.
(b) Exhaustible sources of energy are those which will be exhausted some day
and cannot be regenerated. Inexhaustible sources of energy are those which
can be regenerated again due to some continuing or repetitive currents of
energy and are inexhaustible.
 Options in both cases are exactly same.

8. The qualities of ideal sources of energy are:
(a) It should be easily accessible, inexhaustible and a renewable source of energy
and cost of harnessing energy should be reasonably small.
 (b) It should be easily stored and transported.
 (c) It should have high calorific value.
 (d) It should be pollution free.

9. Advantage of solar cooker:
 a. There is no cost of fuel.
 b. It is environment friendly and there is no residue like ash etc.
 c. Cooking is hygienic and nutritious.
 Disadvantage of solar cooker:
 a. The cooking is slow.
 b. It cannot be used at all times.
 c. A solar cooker can perform only limited functions.

10. The increasing demand for energy is largely being met by the use of fossil fuels. But
these fuels are exhaustible and non-renewable sources of energy. Moreover, burning
of fossils fuels cause air pollution. Release of acidic oxides leading to acid rain that
affect our water and soil resources. These gases also produce greenhouse effect
leading to increase the temperature of earth.
To reduce energy consumption we should lead a simple and a natural life. As an
example, instead of using an air conditioner in a closed room we should live in an
airy room having appropriate number of windows.

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