A wind turbine uses electromagnetic induction to generate electricity. During a storm, the turbine blades spin much faster than normal. Explain how electricity is generated in the turbine and what effect the faster spinning has on the electricity produced.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Wind turbines contain a large coil of wire that rotates inside a magnetic field. They are connected to the national grid to supply homes and businesses with electricity.
Model answer (4 marks)
A rotating coil in a magnetic field cuts magnetic field lines, which by Faraday’s law induces a potential difference across the coil.
The induced voltage is proportional to the rate at which the coil cuts the field lines.
When the turbine blades spin faster, the coil cuts the field lines more quickly.
This higher rate of cutting increases the induced voltage, so a larger current flows and more electricity is produced.
The induced voltage is proportional to the rate at which the coil cuts the field lines.
When the turbine blades spin faster, the coil cuts the field lines more quickly.
This higher rate of cutting increases the induced voltage, so a larger current flows and more electricity is produced.
Examiner tips
- Use the phrase ‘Faraday’s law’ or ‘induced voltage’ to show knowledge of the principle.
- Show the proportionality between speed and voltage – e.g. ‘rate of cutting field lines’.
- Mention the effect on current and power output.
- Keep the answer concise – 4 short points is enough for full marks.
Common mistakes
- Confusing the direction of the induced current with the direction of rotation.
- Failing to link the faster spinning to an increased rate of cutting field lines.
- Using vague terms like ‘more electricity’ without explaining the voltage/current relationship.
Mark scheme (4 marks)
- The rotating coil cuts through magnetic field lines (or the magnetic field lines cut through the coil)
- This induces a potential difference (or voltage) across the coil
- Faster spinning means the coil cuts field lines more quickly / the rate of cutting field lines increases
- This increases the induced potential difference (so a larger current flows / more electricity is produced)
Key terms in this question
Related
- All OCR GCSE Physics A: Gateway Science (J249) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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