A wind turbine uses electromagnetic induction to generate electricity. The turbine blades turn a coil of wire inside a magnetic field. Explain why a greater wind speed produces a larger induced EMF in the coil.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Wind turbines generate electricity for homes and businesses. Inside the turbine, a coil of wire rotates within a magnetic field. On a calm day the blades rotate slowly; on a windy day the blades rotate much faster.
Model answer (5 marks)
A greater wind speed causes the coil to rotate faster, increasing the rate of rotation of the coil.
The coil cuts through the magnetic field lines more frequently, so the magnetic flux through the coil changes more rapidly.
This increase in the rate of change of flux means the induced EMF is larger, because the induced EMF is proportional to the rate of change of flux.
A larger induced EMF drives a larger current through the circuit, producing a greater electrical output.
The coil cuts through the magnetic field lines more frequently, so the magnetic flux through the coil changes more rapidly.
This increase in the rate of change of flux means the induced EMF is larger, because the induced EMF is proportional to the rate of change of flux.
A larger induced EMF drives a larger current through the circuit, producing a greater electrical output.
Examiner tips
- Use the exact phrase "rate of change of flux" and link it to EMF. Show the chain: wind speed → rotation speed → flux change → EMF → current. Mention the coil cuts field lines more often.
- common_mistakes
- :
- Saying the magnetic field itself is stronger; it is the flux change that matters. Forgetting to connect the faster rotation to a higher rate of flux change. Using vague terms like "more electricity" without explaining the EMF link.
Mark scheme (5 marks)
- A greater wind speed causes the coil to rotate faster / increases the rate of rotation of the coil
- The magnetic field lines are cut more frequently / the coil cuts through magnetic field lines more quickly
- This increases the rate of change of flux / the magnetic flux changes more rapidly
- A larger induced EMF is produced because the induced EMF depends on / is proportional to the rate of change of flux
- A larger induced EMF drives a larger current through the circuit / produces a greater electrical output
Key terms in this question
electromagnetic induction · induced EMF · coil
Related
- All WJEC A-Level Physics (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Electromagnetic induction questions
- A bicycle dynamo contains a coil of wire that rotates inside a magnetic field. A…
- A generator in a power station uses electromagnetic induction to produce electri…
- A straight copper wire is held between the poles of a horseshoe magnet. The wire…
- A student moves a bar magnet into a coil of wire connected to a sensitive ammete…