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A simple battery converts chemical energy into electrical
energy. Condensers, or batteries can store small amounts of
electrical power. But it’s not possible to store the great quantities
that we use every day in our homes and in industry. The
generating stations must be operating continuously to cope with
this demand. There are certain times during the day, when this
demand for power is very high and other times when it may be
very low. These are known as peak and off-peak periods. In order
to operate the power stations more efficiently they are all
connected to a grid system, which is a network of high voltage
cables to ensure a more even distribution of power all over the
country.
A great natural source of electricity is lightning. The
dazzling flash of light we see during a thunderstorm is caused by
the discharge of electricity from one cloud to another. Sometimes
the discharge may be from a cloud to earth. In this case the
electricity may pass through a tree or a house. When this happens
we say that the house is struck by lightning. To avoid the risk of
damage to buildings a lightning conductor is used. It is made
from a metal rod placed high on the building, which is connected
by a thick conductor wire to a metal plate buried in the earth. If
lightning strikes the building, the charge is conducted safely to
earth.
Electricity and magnetism are closely connected. Each may
be used to produce the other.
Around the poles of a magnet is an area called a magnetic
field. In this area the magnet exerts its attraction. The directions
of this attraction and the shape of the magnetic field are shown by
lines of force. These lines of force can be seen if a small magnet is
placed under a sheet of paper onto that iron filings are sprinkled.

II

When an electric current flows through a conductor, a
magnetic field is set up around it. The conductor becomes a
magnet. If a conductor is made to rotate in a magnetic field, a
pressure of electricity, called a voltage, is produced in it. This is

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