Mains Electricity - Earthing.
If the outer
casing (the outside bit) of an appliance
is a conductor (made of metal), then it can be made safe by Earthing.
The Earth wire usually carries no
electricity,
it is connected to the metal case on
the inside of the appliance.
If something goes wrong inside the appliance
and the Live wire touches the metal
case,
then the Earth wire acts like a
Neutral
wire
and completes the circuit for the
electricity.
A very large current suddenly
flows
because the metal case has little resistance.
This large current blows the fuse in the
plug
and disconnects the appliance from the power
supply.
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