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?
(c) Nuclear energy is released during nuclear fission and fusion. In
nuclear fission, uranium atom is bombarded with low-energy neutrons.
Hence, uranium atom splits into two relatively lighter nuclei. This
reaction produces huge amount of energy. In nuclear fusion reaction,
lighter nuclei are fused together to form a relatively heavier
nuclei. The energy required to fuse the lighter nuclei is provided by
fission reactions. This reaction produces tremendous amount of
energy. These reactions can be carried out in the absence or presence
of sunlight. There is no effect of sunlight on these reactions.
Hence, nuclear energy is not ultimately derived from Sun’s
energy.
Geothermal
energy, wind energy, and bio-mass are all ultimately derived from
solar energy.
Geothermal
energy is stored deep inside the earth’s crust in the form of
heat energy. The heating is caused by the absorption of atmospheric
and oceanic heat. It is the sunlight that heats the atmosphere and
oceans.
Wind energy is harnessed from the blowing of winds. The uneven
heating of the earth’s surface by the Sun causes wind.
Bio-mass is derived from dead plants and animal wastes. Chemical
changes occur in these dead plants and animal wastes in the presence
of water and sunlight. Hence, bio-mass is indirectly related to
sunlight.
Question 4:
Compare
and contrast fossil fuels and the Sun as direct sources of energy.
Fossil
fuels are energy sources, such as coal and petroleum, obtained from
underneath the Earth’s crust. They are directly available to
human beings for use. Hence, fossil fuels are the direct source of
energy. These are limited in amount. These are non-renewable sources
of energy because these cannot be replenished in nature. Fossil fuels
take millions of years for their formation. If the present fossil
fuel of the Earth gets exhausted, its formation will take several
years. Fossil fuels are also very costly.
On the
other hand, solar energy is a renewable and direct source of energy.
The Sun has been shining for several years and will do so for the
next five billion years. Solar energy is available free of cost to
all in unlimited amount. It replenishes in the Sun itself.
Question 5:
Compare and contrast bio-mass and hydro electricity as sources of
energy.
Bio-mass
and hydro-electricity both are renewable sources of energy. Bio-mass
is derived from dead plants and animal wastes. Hence, it is naturally
replenished. It is the result of natural processes. Wood, gobar
gas, etc. are some of the examples of bio-mass.
Hydro-electricity,
on the other hand, is obtained from the potential energy stored in
water at a height. Energy from it can be produced again and again. It
is harnessed from water and obtained from mechanical processes.
Question 6:
What are the limitations of extracting energy from −
(a) the
wind? (b) waves? (c) tides?
(a) Wind energy is harnessed by windmills. One of the limitations of
extracting energy from wind is that a windmill requires wind of speed
more than 15 km/h to generate electricity. Also, a large number of
windmills are required, which covers a huge area.
(b) Very strong ocean waves are required in order to extract energy
from waves.
(c) Very high tides are required in order to extract energy from
tides. Also, occurrence of tides depends on the relative positions of
the Sun, moon, and the Earth.
Question 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?
(a) The source of energy that replenishes in nature is known as
renewable source of energy. Sun, wind, moving water, bio-mass, etc.
are some of the examples of renewable sources of energy.
The source of energy that does not replenish in nature is known as
non-renewable source of energy. Coal, petroleum, natural gas, etc.
are some of the examples of non-renewable sources of energy.
(b) Exhaustible sources are those sources of energy, which will
deplete and exhaust after a few hundred years. Coal, petroleum, etc.
are the exhaustible sources of energy.
Inexhaustible resources of energy are those sources, which will not
exhaust in future. These are unlimited. Bio-mass is one of the
inexhaustible sources of energy.
Yes.
The options given in (a) and (b) are the
same.
Question 8:
What are the qualities of an ideal source of energy?
An ideal source of energy must be:
I. Economical
II. Easily
accessible
III. Smoke/pollution
free
IV. Easy
to store and transport
V. Able
to produce huge amount of heat and energy on burning
Question 9:
What are
the advantages and disadvantages of using a solar cooker? Are there
places where solar cookers would have limited utility?
Solar
cooker uses Sun’s energy to heat and cook food. It is
inexhaustible and clean renewable source of energy. It is free for
all and available in unlimited amount. Hence, operating a solar
cooker is not expensive.
Disadvantage
of a solar cooker is that it is very expensive. It does not work
without sunlight. Hence, on cloudy day, it becomes useless.
The places
where the days are too short or places with cloud covers round the
year, have limited utility for solar cooker.
Question 10:
What are
the environmental consequences of the increasing demand for energy?
What steps would you suggest to reduce energy consumption?
Industrialization
increases the demand for energy. Fossil fuels are easily accessible
sources of energy that fulfil this demand.
The increased use of fossil fuels has a harsh effect on the
environment. Too much exploitation of fossil fuels increases the
level of green house gas content in the atmosphere, resulting in
global warming and a rise in the sea level.
It is not
possible to completely reduce the consumption of fossil fuels.
However, some measures can be taken such as using electrical
appliances wisely and not wasting electricity. Unnecessary usage of
water should be avoided. Public transport system with mass transit
must be adopted on a large scale. These small steps may help in
reducing the consumption of natural resources and conserving them.
