Wiring a plug

Appliances are connected to the main ring using 3-pin plugs: two short pins and one longer one.

The wires and pins must always be connected in the same way, so they made the wires in the connecting lead are colored code.

The wires and pins must always be connected in the same way, so they made the wires in the connecting lead are colored code.

Brown = live Blue = neutral Green/Yellow = earth

If you touch a live wire at about 230V, an electric current can pass through your body, which will cause electric shock and you can be killed. That's why ring-mains and lighting circuits have an earth wire, to protect ourselves.

Earthing

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to light bulb

to light bulb

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8 9

Explanation

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one end of the earth wire is connected to the metal base of the lamp...... the other end is connected to the earth pin in the pluga wire leads from the earth pin in the socket...... to a metal plate buried in the earth

metal base

path of current

bare live wire touches case

The current normally flows to and from the light bulb along the live and neutral wire

If the insulation wears through, the current flows through the metal to the earth wire

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3

4

to light bulb

to light bulb

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8 9

Residual current circuit breakers

A residual current circuit breaker can be used to protect against a fault which makes the outside of a properly earthed appliance become live, and where the current in the earth wire is not enough to blow a fuse (this can be very dangerous).

A residual current circuit breaker contain an electromagnetic switch in order to quickly turn off the power if the current in the earth wire is bigger than 0.03A.

Circuit breakers like this are recommended for use with lawn mowers, portable tools (electric drill), and school laboratories.

No earth wire!

Appliances marked "double insulated" do not have an earth wire, because their metal parts are covered with insulating plastic, so it won't give the user shocks.