GCSE Physics · Edexcel 1PH0 · Topic 13B
Transformers and the National Grid
Key points
- A transformer has two coils on a soft iron core. An alternating current in the primary coil makes a changing magnetic field, which induces an alternating pd in the secondary coil. It only works with a.c.
- Turns ratio: . A step-up transformer has more turns on the secondary; a step-down has fewer.
- For a 100% efficient transformer, power in = power out: .
- The National Grid transmits electricity at very high pd (hundreds of thousands of volts) so the current is low.
- Low current means less heating in the cables (), so less energy is wasted.
- Step-down transformers near homes reduce the pd to about 230 V for safe use.
Topic notesPremium
A transformer uses electromagnetic induction to change the size of an alternating potential difference. Transformers make the National Grid possible, letting electricity travel hundreds of kilometres while wasting very little energy.
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