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Design & Technology

Components

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

BatteryVoltage
AAA1.5V
AA1.5V
C1.5V
D1.5V
PP39V

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.

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