Transformers (HT 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
Examiner Tip
Make sure you're confident with explaining how a transformer works. You should also be detailed in your answer in the exam and use key terms such as 'induce' instead of 'creates' or 'makes' and refer to a changing magnetic field, as this is very important, otherwise, the potential differences would not be induced!
