A wind turbine uses the generator effect to supply electricity to homes in a village. The turbine's rotating coil spins between two permanent magnets. Explain how the generator effect produces a current in the coil and why the current supplied to the homes is alternating.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Wind turbines are increasingly used to generate electricity. Inside a wind turbine, a coil of wire rotates between two permanent magnets as the blades spin in the wind.
Model answer (5 marks)
A rotating coil is a conductor that moves relative to a magnetic field, so it cuts magnetic field lines.
This motion induces a potential difference across the two ends of the coil.
Because the coil is part of a closed circuit, the induced potential drives a current.
As the coil turns, the direction in which it cuts the field lines reverses every half‑turn.
Thus the induced current changes direction continuously, giving alternating current.
This motion induces a potential difference across the two ends of the coil.
Because the coil is part of a closed circuit, the induced potential drives a current.
As the coil turns, the direction in which it cuts the field lines reverses every half‑turn.
Thus the induced current changes direction continuously, giving alternating current.
Examiner tips
- Use the word "induce" for the EMF, not "create"; mention the coil is part of a complete circuit; explain the reversal every half‑turn; keep the answer concise and use UK spelling.
- Structure the answer in 5 clear points matching the mark scheme.
- Use the phrase "rotating coil" and "permanent magnets" to show understanding of the setup.
Common mistakes
- Saying the coil is stationary and the magnets move; the relative motion is key.
- Forgetting to mention that the coil is part of a complete circuit, so current flows.
- Claiming the current is DC because the coil is a conductor, ignoring the reversal every half‑turn.
Mark scheme (5 marks)
- The rotating coil (conductor) moves relative to the magnetic field / cuts through the magnetic field lines
- This induces a potential difference across the ends of the coil
- Because the coil is part of a complete circuit, a current flows
- As the coil rotates, the direction in which it cuts the field lines reverses (every half turn)
- This causes the direction of the current to constantly reverse / change direction, producing alternating current
Key terms in this question
Related
- All OCR A-Level Physics A (H556) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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