Electricity Generation
Energy Efficiency
Mains Electricity

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Mains Electricity

The Plug

This is what a plug looks like under the cover. The wire colours are the same almost everywhere, but the components and positions will vary depending on where you live.


Be aware that electricity is very dangerous, so don't play around with plugs unless you know what you are doing (and make sure they aren't connected).

symbol for double insulation This symbol on a specification plate means the product is double insulated. Meaning it has a fully plastic casing with nothing sticking out. Therefore, it has no earth wire, since there is no risk of the casing becoming live.

The fuse is yet another safety measure, they break the circuit if the current is too high, by way of a thin wire breaking

An alternative to fuses is a circuit breaker. These don't have to be replaced like fuses - merely reset. They also work quicker. They work by breaking the circuit when the current in the neutral wire is less than in the live.

Important Equation

The equation triangle below shows the important relationship between power, current and voltage.

power current voltage


Now we look at how you can calculate the cost of individual appliances: could help you save money on the electricity bill. Have a look at the example below:

A kettle uses 8kW and is used for a total of 1h30m in a month. Calculate the cost if 1 unit is 7p.

Cost = kWh x cost per unit
= 8 x 1.5 x 0.07
= £0.84