Transformers (OCR GCSE Physics A (Gateway)) : Revision Note

Transformer

Higher Tier Only

• A transformer is a device used to change the value of an alternating potential difference or current

  • This is achieved using the generator effect (electromagnetic induction)

• Transformers use the effect of an alternating current in one circuit to induce a current in another

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

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