Metals are good conductors,
which means that electric charges
move easily through them.
Materials such as plastic, wood, glass and
polythene are insulators, this means they don't
allow electric charges to move through them.
Some insulators can
become electrically charged
when they're rubbed together.
How can you tell if an
insulator is charged?
If a plastic rod is rubbed with a duster it
attracts small pieces of paper
When a balloon is rubbed on a jumper
it can stick to a wall.
Positive & Negative charges
Objects can be positively
charged, negatively charged
or neutral (no charge).
A substance that gains electrons becomes
negatively charged, while a substance that
loses electrons becomes positively charged.
When an acetate rod is rubbed with a
duster, electrons are transferred from
the rod onto the duster, making the
rod positively charged.
Atoms or molecules that
become charged are ions.
Electric shocks
You can get an electrostatic shock from charged objects, such as clothing made from nylon.
You can get an electrostatic shock if you are charged & you touch something that is earthed.
Problems with static electricity
Dust and dirt is attracted to
insulators such as TV screens
and computer monitors
Clothes made from synthetic materials
often cling to each other and to the body,
especially just after they've been in a
tumble drier.
There are flammable gases or
vapours or a high concentration of
oxygen. A spark could ignite the
gases and cause an explosion
You touch something with a large
electric charge on it. The charge
will flow through your body
causing an electric shock. This
could cause burns or even stop
your heart.
Safety measures
The chance of receiving
an electric shock can be
reduced if:
An object that might become charged is earthed by
an earth wire, so any charge immediately flows
down the earth wire
In a factory, machinery operators stand on
insulating mats or wear shoes with insulating soles.
Stopping any charge flowing through them to earth.
Lorries containing flammable gases, liquids and
powders are earthed by an earth wire before being
unloaded. Charge immediately flows down the earth
wire preventing a spark/ explosion.
Anti-static sprays, liquids and cloths
prevent the build-up of charge by
allowing it to conduct away.