A wind turbine generates electricity by rotating a coil of wire inside a magnetic field. State two ways the induced voltage could be increased by changing the coil, and for each change, explain why the voltage increases.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Wind turbines use the generator effect to produce electricity for homes. Engineers can alter the design of the coil inside the turbine to change the output voltage.
Model answer (4 marks)
1. Increase the number of turns in the coil.
More turns mean the coil cuts the magnetic flux more times per rotation, so the induced emf (ε = NΔΦ/Δt) is larger.
2. Increase the area of the coil.
A larger area gives a greater magnetic flux (Φ = B·A) for the same field, so the change in flux per unit time is greater, raising the induced emf.
More turns mean the coil cuts the magnetic flux more times per rotation, so the induced emf (ε = NΔΦ/Δt) is larger.
2. Increase the area of the coil.
A larger area gives a greater magnetic flux (Φ = B·A) for the same field, so the change in flux per unit time is greater, raising the induced emf.
Examiner tips
- Use the formula ε = NΔΦ/Δt to justify the effect of more turns. Use Φ = B·A to justify the effect of a larger area. Show the relationship between flux change and induced voltage.
- common_mistakes
- :
- Confusing the number of turns with the length of wire; only the number of turns matters for emf. Failing to mention the flux–area relationship when explaining the area change. Using the wrong formula (e.g. ε = B·l·v) without linking it to the coil changes.
Mark scheme (4 marks)
- Increasing the number of turns on the coil (increases the induced voltage)
- More turns means a greater length of wire is cutting through / experiencing the magnetic field, so a greater voltage is induced
- Using a larger area coil (increases the induced voltage)
- A larger area coil has a greater length of wire inside the magnetic field, so a greater voltage is induced
Key terms in this question
induced voltage · magnetic field · coil
Related
- All Pearson Edexcel International GCSE Physics (4PH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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