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Electricity, a term derived from the Greek word for amber, has
been a mysterious force since the Greeks first discovered it thousands of years
ago. They found that rubbing a piece of amber with fur would cause it to attract
light materials such as straw. Later, scientists discovered that other materials
could also hold charges of electricity, and today, we can produce such charges
by running a comb through our hair or shuffling across a thick rug. However,
before electricity could become the servant it is today, scientists had to
discover a great deal about it.
To understand electricity, scientists had to first comprehend the smallest units
of matter: atoms, which are made up of electrons that can move from atom to
atom. These particles form an electric current, which is defined as a stream of
electrons moving through certain materials. Italian scientist Volta discovered a
way of obtaining an electric current more than 150 years ago, but his electric
bell only produced a weak current and was not very useful. It was not until
British scientist Michael Faraday invented a machine that could push electrons
and produce a current of electricity that electricity became more practical.
Faraday's machine was the forerunner of modern generators.
Nowadays, we use both electric cells and generators to supply currents of
electricity. A battery made up of two or more electric cells joined together is
used in portable radios, hearing aids, motor vehicles, and electric toys. Such
cells are made up of zinc and carbon with a moist mixture of chemicals in
between. Generators are made up of magnets and coils of wire that must be
whirled around to start the electrons moving and begin the current. Electric
power plants are often located near waterfalls and dams, and steam turbines are
also used to turn generators.
Electricity is used to power our homes, shops, streets, and offices. We use it
for lighting, fans, cookers, and all types of modern electrical appliances, from
light bulbs to elaborate electrically driven machines. Electric machines can
lift loads of iron, take X-ray pictures, and even replat silver knives and
forks. However, before ordinary people could enjoy these benefits, scientists
and electricians had to learn a great deal about the use and control of
electricity. Setting up a flow of electrons and turning on a switch is only the
beginning. Circuits or paths for the current must be established, and ways of
starting and stopping the current must be easy.
Electricity will flow more easily through some substances called good conductors
than others called bad conductors, and circuits of electricity are made by wires
that bring the electricity from the power plants to our homes. All we need to do
is to switch it on or plug it in. This action joins the wires in the plug or
switch to the wires connected to the generator, and the circuit is complete. It
is broken when the switch is turned off or the plug is removed.
The development and use of electricity for all our home appliances, television
sets, transport, and telegraph systems owes a great debt to scientists like
Faraday and others who wrote out the many signs now seen in electric lights all
over the world that say, "Electricity, your servant." Although it may seem
simple, the discovery and development of electricity has taken many years and a
great deal of effort to make it the indispensable servant of modern civilization
that it is today. |
