AQA GCSE Physics

Revision Notes

7.3.5 Transformers

Higher Tier Only


  • A transformer is an electrical device that can be used to increase or decrease the potential difference of an alternating current
    • This is achieved using the generator effect

Structure of a Transformer

  • A basic transformer consists of:
    • A primary coil
    • A secondary coil
    • An iron core
  • Iron is used because it is easily magnetised

Transformer Diagram, downloadable AS & A Level Physics revision notes

Structure of a transformer

How a Transformer Works

  • An alternating current is supplied to the primary coil
  • The current is continually changing direction
    • This means it will produce a changing magnetic field around the primary coil
  • The iron core is easily magnetised, so the changing magnetic field passes through it
  • As a result, there is now a changing magnetic field inside the secondary coil
    • This changing field cuts through the secondary coil and induces a potential difference
  • As the magnetic field is continually changing the potential difference induced will be alternating
    • The alternating potential difference will have the same frequency as the alternating current supplied to the primary coil
  • If the secondary coil is part of a complete circuit it will cause an alternating current to flow

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