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Mains Electricity - Double Insulation.
Some appliances are double
insulated.
These appliances only need Live and Neutral wires,
they do not need an Earth
wire.
An appliance which is double
insulated
has the whole of the inside contained in plastic,
underneath an outer casing.
If anything goes wrong with the appliance,
no Live conductor can touch the
outer casing
because of the
insulating plastic.
Appliances which are
double insulated include
electric drills and hairdryers.
The symbol for double insulation is shown below.
You will see this symbol printed on the appliance which is double
insulated.
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