Electrical Transformer

Key Stage 4

A picture of a transformer in the National Grid.

A transformer is a device used to take the alternating current in a circuit and transmit it to another circuit to produce electricity with a different potential difference and current.

Transformers use a coil of wire in one circuit (primary coil) wrapped around a soft iron core and second coil of wire in another circuit (secondary coil). When an alternating current passes through the primary coil this creates a changing magnetic field which induces an alternating potential difference across the secondary coil. If that secondary coil is connected in a circuit it will produce an alternating current.


This diagram of a transformer shows that an alternating current in the primary coil induces an alternating potential difference in the secondary coil.