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Mains Electricity - What is Insulation?

Insulation means putting a material that does
not conduct electricity around a live conductor.
A material that does not
electricity is called an insulator.

The word "insulator" is also used for a material
that slows down the rate of heat transfer.

Which Materials are Good Insulators?

Any metal is a good conductor of electricity.
Any non-metal is a good insulator, with
the exception of graphite which conducts electricity
because of its unusual molecular structure.
To find out what is a metal and what is a non-metal,
see the GCSE Chemistry site at the periodic table.

The wires that are used to conduct electricity
are made of a high purity copper metal.

The insulator that covers the wires is a polymer called PVC
(often just called "plastic"). It is a good insulator,
flexible enough to bend round corners and cheap to make.
Older wires were insulated with a rubber material
but the rubber cracked and split as it aged. It has been
replaced in houses by new PVC covered cable. This
is an example of a new material
replacing an older one
because the new material has
superior properties.

Insulation can become unsafe if it is damaged or
if it is wet because impure water will conduct electricity.

Some appliances have double insulation.

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