A wind turbine generates electricity for a remote farmhouse. The turbine contains a coil of wire that rotates between two permanent magnets. Explain how the rotating coil produces an alternating current that can be used to power electrical appliances in the farmhouse.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Wind turbines are used in rural areas to generate electricity. Inside each turbine, a coil of wire is made to spin by the turning blades.
Model answer (5 marks)
1. The rotating coil cuts through the magnetic field produced by the permanent magnets.
2. This motion induces a potential difference across the coil’s ends (generator effect).
3. Because the coil is part of a closed circuit, a current flows.
4. As the coil turns, the induced voltage changes sign, so the current direction reverses repeatedly.
5. The result is an alternating current whose frequency is set by the coil’s rotation rate, suitable for powering appliances.
2. This motion induces a potential difference across the coil’s ends (generator effect).
3. Because the coil is part of a closed circuit, a current flows.
4. As the coil turns, the induced voltage changes sign, so the current direction reverses repeatedly.
5. The result is an alternating current whose frequency is set by the coil’s rotation rate, suitable for powering appliances.
Examiner tips
- Use the word ‘induced’ and ‘generator effect’ to show understanding of Faraday’s law.
- Show the link between coil rotation and sign change of the induced EMF.
- Mention that the AC frequency equals the rotation frequency of the coil.
- Keep the answer concise – one sentence per point.
Mark scheme (5 marks)
- The rotating coil moves relative to (cuts through) the magnetic field
- This induces a potential difference across the ends of the coil (generator effect)
- A current flows because the coil is part of a complete circuit
- As the coil rotates, the direction of the induced current reverses repeatedly / continually changes direction
- This produces alternating current (AC), which changes direction at a set frequency / matches the rotation frequency of the coil
Key terms in this question
Related
- All OCR A-Level Physics B: Advancing Physics (H557) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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