GCSE Physics · AQA 8463 · Topic 4.7.3
Induced potential, transformers and the National Grid
Key points
- (Higher tier) The generator effect: moving a conductor relative to a magnetic field, or changing the field through a coil, induces a potential difference. If the circuit is complete, a current flows.
- The induced current makes its own field that opposes the change that caused it. A faster movement or stronger field gives a larger p.d.
- An alternator uses slip rings to produce a.c.; a dynamo uses a split-ring commutator to produce d.c. A microphone turns sound into electrical signals.
- A transformer has primary and secondary coils on an iron core. It only works with a.c.
- Transformer equation: . For 100% efficiency, .
- Step-up transformers (more turns on the secondary) raise the p.d.; step-down transformers lower it.
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(Higher tier) This whole sub-topic is Higher tier only. Moving a wire through a magnetic field, or changing the field through a coil, induces a potential difference. That is how power stations generate electricity, how microphones work and…
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