What does the fuse do in a three-pin plug?

Answer 1

The 3 pin plug is used to connect (and eventually disconnect) various devices requiring an AC power supply to and from the main power supply.

As the name suggests, the 3 pin plug consists of three pins :-

1. Longer one, usually on the top for most standard plugs : is the earth [ E ]
2. Left pin (Usually) : is the Line connection [ L ]
3. Right pin (Usually) : is neutral [ N ]

Next to the pins, on the plug, the three pins and their respective function is given by E, L and N.

Answer 2

The fuse is a special cartridge with thin wire in it, so that if excessive current flow, the fuse is the first thing to melt and disconnect the supply. That prevents a possible fire in the house wiring.

Answer 3

A 3 pin plug works in a very simple way.

Inside your wall are 3 cables live/hot, neutral and earth.
Live and neutral carry the electricity in normal conditions, and the earth cable is only there for protection.

Now, please consider that the cables in your wall don't stop in your socket they only pass through it (they must come from somewhere and go on to the next socket and the next...). When we put a plug into the wall we are connecting it to the cables in a T shape (the horizontal part of the T is the cable in the wall and the vertical part is the plug). OK so we have three pins on the plug so, we actually have 3 T's, one for each cable (live, neutral and earth). All this does is allow us to plug multiple plugs into the same socket circuit.
Simply speaking, a plug is an easy way to connect and disconnect part of an electrical circuit, in this case your TV, toaster or whatever has the plug on it.
When you plug it in the device is connected to the supply, and when you plug it out it is not connected to the supply.

Inside the plug there are 3 connections, a fuse and a cable grip. These should be clearly marked on the outside of the plug. Be careful not to mix these up if you have too turn the plug upside down to look at them.

Inside a fuse is a very thin piece of wire with a particular current rating (in Amps). Now take an example fuse of 13 amps.
When the current going through the fuse goes above 13A usually because of a fault or overloading (too many things plugged into the same socket board) the fuse will break/blow.
The fused connection is always connected to the live wire.

The reason being that if you measure the potential difference (voltage) between neutral and earth it "should" be 0 volts.
If you measure the volts between live and neutral or live and earth you will get full voltage (since I'm from Ireland this will measure 230V for me).
If you connect the fuse to the neutral wire it will still break when there is a problem.
However when we measure the voltage inside our device we will have
Between: neutral and earth 0 volts
Live and neutral 0 volts (because the neutral is now broken)
Live and earth 230 volts (because the fuse is on the neutral)

This means that while the device is not working it is still live inside and as such can give someone a potentially lethal shock.

As usual if you have any doubts please contact an electrician.

Answer 4

A fuse in any application is to prevent an over current condition from harming the wiring and components in a circuit.