The electricity supply to homes in the UK is alternating current, written a.c. This means the current keeps reversing direction, instead of flowing one way as it does from a battery.
The supply has a frequency of 50 Hz. Frequency is the number of cycles per second, measured in hertz (Hz). One cycle is a complete forward and backward swing of the current, so at 50 Hz the supply completes 50 cycles every second and the current changes direction 100 times every second.
The potential difference of the domestic supply is about 230 volts (230 V). Mains appliances such as kettles, lamps and hairdryers are designed to work from this supply.
