Energy

Energy is the name given to the ability to do work. There
are various forms of energy such as Mechanical Energy,
Chemical Energy, Electrical Energy, Atomic Energy or Solar
Energy. Energy of various kinds is often made available by
chemical changes. It can also be produced from physical
changes. The following are examples of how energy is used.
 
The jet aircraft gets its power from jet turbines. These
powerful jet engines create a high-pressure stream of very
hot gases that push the aircraft forward as they leave the
engine. This is an example of heat being transformed into
movement or Mechanical Energy. However, this transformation
could not take place without the fuel that the aircraft
gets within its wings or fuselage. Fuel is considered a
chemical energy.
 
Fuel can take the form of gases, solids or liquids. When
fuels combine with oxygen from the air, they release their
stored energy as heat. This process is called burning. The
individual relies on food for fuel which contains
energy-giving substances that our bodies can store until we
need this energy to use our muscles. When we do use our
muscles within us, we may not always be sure that heat is
given off. Our bodies do not burst into flames but the
perspiration on our skin is a clue to what is happening.
 
The movement of the windsurfer has a different explanation.
The windsurfer is propelled along by a sail which collects
mechanical energy from the winds that sweep along the
water. This energy has been produced by the sun which warms
the earth's surface and sets the air above in motion. The
sun's heat comes to the earth as a form of radiant energy.
When the heat reaches the surface of the earth, it causes
the land or seas to rise in temperature.
 
The sun is very hot. In fact, the center of the sun can
reach temperatures of up to 27 million degrees Fahrenheit.
This is because of another kind of energy reaction where
new substances are continually being created as others are
being destroyed. This reaction is known to us as the
Nuclear Reaction. Today we are trying to imitate this
reaction in improving our energy supply. Scientists have
calculated that the sun has enough fuel to go on producing
energy at its present rate for about five billion years.
 
On earth man-made nuclear reactions are used to produce a
form of power we know as electricity. Electricity can be
transformed into other kinds of energy such as heat, light
and radio waves. Humans have also used the idea of nuclear
reactions as a type of weapon. We call this powerful weapon
the Atomic Bomb. Electrical energy can also be used to
produce laser beams. This involves energy being
concentrated to a specific narrow point where the impact of
so much power creates heat able to cut through metals. 
 
Bibliography:
 
Frazer, Frank Trewin. Discovering Energy. Copplestone Books
Ltd, 1981. 

"Energy" Encyclopedia Britannica, Vol. 6 Encyclopedia
Britannica, 1979.