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Energy
By Terry Bell
All
forms of energy are important, whether man-made like electricity, or natural like
wind-power. Basically, it is energy that makes the world go round. But, what are
the different forms of energy? How are they formed? Can we find and develop new
sources of energy? Questions like these are discussed in the following passage.
The sun
is the most important source of energy that the earth has. It gives
out energy in the form of light and heat to plants or animals or people and
helps them to grow. Any changes in the heat produce wind and rain. As the plants
receive energy from the sun, they give out oxygen, which is necessary for human
and animal life. Human beings also take in energy from the sun but this alone
is not enough for a person to live. People also need other forms of energy which
they get by eating plants and meat of animals.
Finding the power of fire was an important step in the changing and growing
use of energy. It was probably discovered by accident when the sun made something
burn—perhaps a dry tree in a hot summer. Soon fire began to be used as a source
of energy. There were many things in the world which would burn and they could
be found easily. There were plenty of bushes and trees and there were also pieces
of black rock which would also burn; this black rock was coal. There were also
pools of oil which burned.
All these things which burn in the air are called fuels and are all natural
materials.
A lot of coal was found on the earth many years ago but most of the coal could
only be found under the ground. The reason for this is that coal was made by
trees which died millions of years ago. The trees sank into mud which was carried
along by rivers; and the wood slowly changed into coal. The coal was buried
deep in the ground by the movement of rocks, earth and plants which pressed
down on it and formed different layers above it. Coal is the same as wood, therefore;
but it burns much longer and produces much more heat so it is more useful as
a source of energy than wood.
Oil was probably made from very small sea animals. When they died, they sank
to the bottom of the sea. The weight of heavy rocks pushed all the dead bodies
together and after many millions of years, they changed into oil. Like coal,
oil is found deep in the earth, often in places which are very difficult to
reach. Men drill into the ground to get oil.
Natural gas is also a fuel; it will burn in air. It is very often found together
with oil sources, caught between the oil and the rocks. At first, when oil was
discovered under the ground, the gas was not considered useful. It
was seen only as one more problem in the search for oil and was burned off so
that the oil could be reached more quickly. But after many years
of burning off the gas, it was realized that the gas was also a useful fuel.
Then gas pipelines were built under the ground so that the gas could be taken
to different parts of the country. Gas can also be taken in liquid form in large
lorries. But this is dangerous because if the liquid gas escapes and reaches
the air it can explode.
A large area of the world is covered with water, most of which is always moving.
It did not take very long before people began to make use of the power of water.
When water falls, the force which is created is quite powerful and it is possible
to turn a large wheel by this force. This wheel will then turn another wheel
which can carry out a certain job such as moving two stones together to cut
corn into small pieces.
Hydro-electricity
(water power) is probably the most-used form of energy given by nature.
There are many countries which use hydro-electricity: India, Pakistan, Egypt,
America, Australia and Uganda all produce power from water and then use the
water again on the land in order to grow food. More than 90% of the electricity
used in Sweden, Norway, Portugal, Switzerland and some South African states is produced by hydro-electric
Apart from water power, people found they could make use of the force of the
wind to create power and windmills were built. The wind turned the windmill
which then turned a large stone in order to make flour out of corn.
Both water and wind power are cheap forms of energy and they are easily available
but they can only create a small quantity of energy. Another problem is that
these forms of energy can only be produced when the weather is right.
All the sources of energy discussed here are natural forms of energy, all created
directly or indirectly by the sun. The natural fuels, such as coal, oil and
gas, are more useful than wind or water power because the amount of energy they
produce is greater. However, burning natural fuels is not the best way to use
them, as much of the energy is wasted: it disappears into the air. But scientists
found that they can put fuels to better use by turning them into a different
form of energy.
For example, if coal is heated in a container without any air, it does not burn
but changes into another form of fuel called .
Coke produces less smoke than coal and is very good for heating but it is quite
difficult to start it burning. As the coal is changed into coke, a gas is also
produced. This gas is called coal gas and can be stored in large containers
called gas-holders and used for heating and lighting. So, from one fuel, two
other more useful forms of energy have been created. Not all coal, however,
is suitable to be made into coke.
The oil which is found under the ground comes to the surface as crude oil. This
means that the oil is in its natural state and has not been changed in any way.
It is, in fact, a mixture of different sorts of oils which can be separated
from each other. To do this, the crude oil is heated and cooled many times and
different parts can then be taken away. Some sorts of oils are used to heat
buildings or to put into machines so that they work efficiently. Others are
especially suitable forms for transport. Probably
the most important function of coal and oil is to heat water for the steam engine,
or steam turbine where electricity is produced. Electricity can then
be supplied to all parts of the country through cables.
A fuel such as coal or oil heats
water in a boiler and steam is produced. The steam is under great pressure
and turns the blades of a turbine. As the turbine turns, electrical energy is
produced through a generator. The electricity is then sent out to houses and
factories.
Instead of using steam to turn the blades of the turbine, electricity can also
be produced by the force of water which falls onto the turbine blades. The amount
of water which falls must be very great, however, and so dams are built to give
the necessary amount of water. Some dams produce large amounts of electricity.
An atom is something very small which cannot be seen by the eye. But it exists;
in fact everything known on the earth is made out of atoms. Atoms join together
to form gases, liquids and solids. All atoms contain energy. About 35 years
ago, scientists began to make use of the energy source which is found in atoms.
They are very small but it is possible to break them into smaller pieces. When
this is done, great heat is produced; this heat can be used to produce electricity
in the same way as the heat produced by burning fuels is used. The heat which
is given off by the atoms, however, is very much greater than any other form
of fuel we know and so more electricity can be made. In Britain and in many
other parts of the world, electricity from atoms, called nuclear energy, provides
one more source of power.
( 1,353 words )
(From Energy, by Terry Bell, Cassell Ltd. )
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