If you turn a television on
and touch the screen, the screen feels as though it has a film of
some sort over it. The tv screen is charged. It has an excess of
electron. Many materials accumulate charge in this way. If for
example you rub a balloon on your clothes, you may cause electrons to
pass from one to the other. If you then hold the balloon close to
running tap water, you may cause it to deflect in the way shown
below.
Static electricity occurs in
nature. Static electricity may build up between the ground and
rainclouds. This happens usually when low air pressure causes high
winds, causing the same effect as in the example above between your
clothes and the balloon. The result is lightning.
Static electricity can be
dangerous and sometimes precautions must be taken against it. This is
especially so at airports when planes are being refuelled. Static
electricity may build up between the tanker and the plane for example
as the fuel is pumped. With the air full of fuel vapour, any tiny
spark could cause an explosion. Hence tanker and plane are earthed,
which disallows any build up of static electricity. Closer to home,
you may build up static electricity on yourself while driving, if you
move about in your seat. When you get out, at a petrol station, the
charge you have built up causes a spark and BANG!
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