AQA GCSE Mains Electricity

AQA GCSE Mains Electricity

Mains Electricity

UK Mains electricity is 230 Volts, 50 Hertz and is Alternating Current (AC)

Alternating means that it will continuously change direction as shown below.

AC and DC

UK Electricity is 50 Hz, this means that the direction changes 50 times per second, so the generator that is producing this electricity, rotates at a rate of 50 times per second!

Different countries will use a slightly different frequency. USA uses 60Hz.

UK Mains Plugs

3 pin plug with live, neutral and earth wires labelled

In the above plug 3 core cable is used, so it contains Live(brown), Neutral(blue) and Earth wire (green-yellow).

Electrical appliances with a metal case need an Earth wire. Appliances with a plastic case are said to be double insulated, they only need two core wire (live and neutral).

Role of the wires

Live wire will carry the alternating potential difference from the mains supply to the appliance. Remember it alternates at 50 times per second in UK. UK Electricity is 50 Hz

Neutral wire will complete the circuit, it should be earthed at 0V at the local substation. In some cases the potential difference of the neutral wire is almost 0V. Without the neutral wire the circuit is incomplete, so it is needed!

Earth wire is Earthed at 0V, it should not carry a current. It will carry a current if the appliance becomes faulty. If the live wire were to break, make contact with electrical case, charges flow onto the case. So, case becomes live.

The Earth wire connects the metal case to Earth, allowing these charges to flow to Earth.

This would prevent an electric shock if someone touches the case.

See our dedicated page on Earth wires.

Practice Questions

1.Describe the difference between two core and three core wire

2. State the colours of the following wires:

Live

Neutral

Earth

3. Explain why both the live and neutral wire is needed for an  electrical appliance to work. 

4. State the function of the cable grip in the plug.

 

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