Mains electricity is the electricity that comes through plugs and is delivered to your homes. It is different to electricity from batteries because the voltage is much bigger and it has an alternating current.
All electricity flows into our homes through cables. There are three wires inside mains cables. The green and yellow wire is the earth and this is used to prevent you from getting an electric shock, this has no voltage. The brown wire is the live which has a voltage which alternates from positive to negative (when compared to earth). The blue wire is the neutral and is earthed to the local substation and also has a voltage very close to zero, it is used to complete the circuit.
Most electrical appliances that you use in your house have plugs on them. Plugs are wired up in a set way. Watch the video below to learn how to wire a plug...
Make sure you know how a plug is wired and the colours of the wires...
The Green and Yellow wire is the earth - this along with the fuse protect the appliance and the user and is found at the top of the plug It is not used if the appliance is double insulated.
The bLue wire is on the Left hand side (the L's go together) is the Neutral wire.
The bRown wire is on the Right hand side (the R's go together) and is the live wire.
Mains electricity can be dangerous and can kill. Most accidents with electricity are electrical shocks. This is where a person conducts the electricity rather than the device. The person conducts the electricity at a much higher current. For this reason there are two main safety devices that are used in homes to keep you safe. Firstly there are circuit breakers. These are electromagnets which can switch off the electricity supply if there is a difference in the current between the live and the neutral wires.
Secondly there are fuses. These contain a thin wire which will melt if the current running through them is too high (remember that the faster the electrical current, the higher the temperature of the wire). There are 3 main types of fuses 3A, 5A and 13A fuses. These fuses will melt if the current going through them is higher than the fuse rating (eg a 3A fuse will melt if 4 Amps of current passes through it.) Fuses can be found in fuse boxes near the mains supply of a house and in plugs.
UK Mains electricity is 230V AC. This means that the voltage is 230V and as it is AC (Alternating Current). This is a much bigger voltage than batteries can supply which usually run at 1 or 2 Volts on a DC (Direct Current) circuit.
AC is used in mains electricity as the changing direction stops the wires from over-heating. If our houses had 230V DC running through them, most would catch fire! Images from The Electronics Club.
For more information on Mains Electricity click on the links below for revision activities...
or complete a lesson from www.skoool.co.uk
Or try this podcast from BBC bitesize (click on the logo to load it)...