Mains Electricity

UK Domestic Electricity Supply

The mains electricity supply in the UK is AC- alternating current.

Alternating current means that the current continually changes direction.

In the UK the electricity supply is 50Hz, this means that the direction of the current changes 50 times a second! The potential difference is 230V.

The other type of current is DC - direct current. This means that the current only flows in one direction.

Mains Electricity, figure 1

Plugs in the UK

The UK has plugs, well every country has plugs but the ones in the UK have three pins.

The pins are made out of brass since it is a good conductor of electricity and won’t rust.

The outside of the plug is made out of plastic since plastic is a good insulator and prevents electric shocks.

Within the plug there are a number of different components, let’s discuss each one with its use.

Mains Electricity, figure 1

Live wire - brown - this carries the alternating potential difference from the supply.

Neutral wire - blue - this completes the circuit, taking the current back to the source.

Earth wire - green and yellow stripes - this is a safety wire to stop the appliance becoming live. If there is an electrical fault the earth wire will carry the current into the earth and prevents the current from entering a human person and harming them.

The fuse is also a safety device. Inside a fuse is a small thin wire. If the current gets too high, it will heat up the wire which will cause it to melt and break the circuit. In the event of this happening, the fuse has to be replaced before the plug will work again.

Mains Electricity, figure 2

Dangers of Mains Electricity

There are a number of dangers with mains electricity.

Firstly, a live wire can be dangerous even when a switch in the mains circuit remains open. The reason for this is that if the circuit became complete, even accidentally, a large potential difference would start and could electrocute someone. This is why poking a plug socket is dangerous. If a circuit is complete, so the current is able to run, then it will.

This also leads into our second danger. Any connection between the live wire and the earth wire will also provide a complete circuit. This can electrocute a person who has not taken adequate precautions.

What are the colours for the live, neutral and earth wires?
Your answer should include: Brown / Blue / Green / Yellow
Explanation: Live - brown Neutral - blue Earth - green and yellow stripes
What is the frequency of the UK mains electricity supply?
Your answer should include: 50Hz / 50
Why are the plug pins made out of brass?
Your answer should include: Conductor / Rust