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Transformers (Edexcel GCSE Physics)
Revision Note
Operation of a 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
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
The Role of Transformers
Higher Tier Only
- A transformer can change the size of an alternating voltage
- They also have a number of other roles, such as:
- To increase the potential difference of electricity before it is transmitted across the national grid
- To lower the high voltage electricity used in power lines to the lower voltages used in houses
- Used in adapters to lower mains voltage to the lower voltages used by many electronic devices
- A step-up transformer increases the potential difference of a power source.
- A step-up transformer has more turns on the secondary coil than on the primary coil
- 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
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