How Transformers Work

A transformer is an electrical device that changes the potential difference (voltage) of an alternating current supply.

  • Step-up transformers increase the potential difference
  • Step-down transformers decrease the potential difference

A basic transformer consists of two coils of wire, which are not connected. These coils are wrapped around an iron core.

1. An alternating current is supplied to the primary coil.

2. The current flows through the primary coil and produces a magnetic field.

  • Since the current keeps changing direction, the magnetic field does as well

3. The iron core is easily magnetised, so the changing magnetic field passes through it.

4. As a result, the changing magnetic field induces a potential difference in the secondary coil.

  • The magnetic field is constantly changing, so the potential difference induced will be alternating.

5. If the secondary coil is part of a complete circuit, then alternating current will flow.

Transformers do not work with direct current (DC) as the magnetic field produced by DC does not change.

Uses of Transformers

Transformers are used:

  • To increase the potential difference (voltage) of an alternating current supply, before it is transmitted across the National Grid.
  • To lower the high voltage of electricity used in power lines to levels suitable for use in homes.

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