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!

Design & Technology


Power supplies

Batteries are the most common source of power used for electrical circuits in schools. They come in a variety of sizes, which can be combined in series battery holders. This allows the voltage produced to be equal to the sum of the batteries used: eg 3 x 1.5 V AA batteries would produce a voltage of 4.5V.

Batteries and Voltage


When choosing a battery, the following should be considered:

  • The power requirements of the circuit.
  • The battery life needed, measured in milliamp hours.
  • The size, shape and weight of the battery.
  • The cost of the battery.
  • Sustainability: could rechargeable batteries be used?
  • Battery disposal: how will the battery be disposed of at the end of its working life?

As an alternative to batteries, external power supplies can be used with low-voltage regulators (such as L7805 and 78L05). Their use is often limited by cost, the need to be attached to the external power supply and the power requirements of the circuit.

Back to Electronics 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.