Transformers (Oxford AQA IGCSE Physics)

Structure of a Transformer

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

  • This is achieved using the generator effect

• A basic transformer consists of:

  • A soft iron core

  • A primary coil (turns of wire around one side of the iron core)

  • A secondary coil (turns of wire around the other side of the iron core)

• Iron is used for the core because it is easily magnetised

The 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

• The changing magnetic field of the core is now 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

Step-Up & Step-Down Transformers

• A transformer consists of a primary and secondary coil

  • The primary coil is the first coil

  • The second coil is the second coil

• A step-up transformer increases the potential difference of the power source

  • A step-up transformer has more turns on the secondary coil than on the primary coil

  • Step-up transformers are used to increase the potential difference of current before it reaches the distribution lines of The National Grid

• A step-down transformer decreases the potential difference of a power source

  • A step-down transformer has fewer turns on the secondary coil than on the primary coil

  • Step-down transformers are used to decrease the potential difference to a safe level before it reaches consumers