GCSE Standard Questions: The Generator
(Electromagnetic Induction)
Q1. The diagram shows the inside of an oil pipeline and a student's design for a meter to measure the flow of oil.
- As oil flows through the pipeline, the oil rotates a turbine wheel.
- Above the turbine wheel is a coil of wire connected to a data logger.
- There is a magnet in the rim of the turbine wheel. The turbine wheel spins and this induces a varying potential difference (p.d.) across the ends of the coil.
- This varying p.d. is recorded by the data logger.
(a) Complete the sentence below by suggesting a word for dotted space: The faster the oil flows through the pipeline, the greater 
the maximum p.d. across the coil.
(1 mark)
(b) Explain why a varying p.d. is induced across the coil even when the rate of flow of oil remains constant.
The p.d. is produced when the magnetic field/flux lines cut through the coil. As the magnet rotates the p.d varies as the distance between magnet and coil changes.
(3 marks)
(c) Suggest two changes to the design of the meter which would increase the maximum p.d. across the coil for the same flow of oil.
any two from:
- move coil closer to the rim/ wheel
- use a more powerful magnet • put more turns (on the coil)
- incorporate a coil with greater area
- insert an iron core or smaller gap between rim / wheel and coil
- accept extra magnets
- do not accept more coils
(2 marks)
(Total 6 marks)
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