# Mains Electricity

## Basics of Mains Electricity

• The UK mains supply is an Alternating Current (AC) system which cycles fifty times per second, also known as the frequency, which therefore is 50 Hertz (Hz).
• The mains electricity in the UK is supplied at 230 Volts (V).
• Every electric device is designed for a certain Voltage and be mindful of this because using a device at a higher voltage than designed may cause it to be damaged and dangerous.
• Direct Current (DC) is a type of electricity in which the flow of electric charge is only in one direction.

## Domestic Electricity

• Household electricity uses AC because it’s safer and can be transported long distances without much loss of energy.
• Electrical appliances convert the electrical energy into other forms. For example, a toaster converts electrical energy into thermal energy.
• The live wire, which is brown, carries the AC to the appliance. The neutral wire, blue, completes the circuit. The earth wire, yellow and green, is a safety wire to prevent electric shocks.
• Three-pin plugs in the UK contain a fuse which is a safety device that will ‘blow’ or melt if too much current flows, disconnecting the circuit.
• The earth wire and fuse together protect the wiring and the user in case of a fault. If a fault causes the live wire to touch the metal casing of an appliance, the metal becomes live.

## Power and Energy

• Power (Watts, W) is the rate of transfer of energy. It is given by the formula `P = VI`, where V is voltage and I is the current.
• Electrical energy can be calculated using the formula `E = P t`, where E is energy in Joules, P is power in Watts, and t is time in seconds.

## Safety Precautions

• Always turn off and unplug appliances before working on them.
• When replacing a fuse, always replace it with one of the same rating.
• Never touch the live wire because touching this wire will cause a serious shock.
• Maintain wiring regularly to ensure it is not frayed or broken, which could cause a shock or fire.

Remember: Always being careful when using electricity. Understanding mains electricity and how it functions is essential in keeping safe when using electrical appliances.