Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!


Household electricity

Electrical supplies can be direct current (DC) or alternating current (AC).The UK mains electricity supply is about 230V at 50 Hz. It can kill if not used safely. Electrical circuits, cables, plugs and appliances are designed to reduce the chances of receiving an electric shock.

Direct current and alternating current

You should know the differences between direct current (DC) and alternating current (AC) electrical supplies.

Direct current

the signal is a flat line at 1.5V

Direct current

If the current [current: Moving electric charges, for example, electrons moving through a metal wire. ] flows in only one direction it is called direct current (DC). Batteries and cells [cell (physics): A component that uses chemical reactions to supply electrical energy. ] supply DC electricity, with a typical battery supplying around 1.5 V. The diagram shows an oscilloscope screen displaying the signal from a DC supply.

Alternating current

the signal is a wavy line

Alternating current

If the current constantly changes direction, it is called alternating current (AC). Mains electricity is an AC supply, with the UK mains supply being about 230 V. It has a frequency [frequency: The number of repetitions per second of a wave. The unit of frequency is the hertz, 'Hz'. ] of 50 Hz (50 hertzhertz: The unit of frequency, symbol 'Hz'. 1 Hz is 1 wave or cycle per second.), which means it changes direction, and back again, 50 times a second. The diagram shows an oscilloscope screen displaying the signal from an AC supply.

Back to Electricity index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.