GENERATORS
4 marks · NormalA simple generator consists of a coil of wire rotating between the poles of a magnet.
Draw a labelled diagram showing a coil rotating between two magnets.
Describe what would happen to the induced voltage if the coil is rotated faster.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Diagram shows a coil between North and South poles, with rotation arrow. Labels: coil, N/S, rotation. · must show coil, N pole, S pole, rotation arrow
(b) If the coil is rotated faster, more field lines are cut per second, so a greater voltage is induced.
Must show: labelled coil, magnet poles (N and S), rotation direction
Common mistakes: Not labelling coil or magnet poles; Not relating voltage and speed
Show mark scheme and worked solution
Marking points
D1 (a) · 1 mark · Coil shown correctly between magnetic poles
D2 (a) · 1 mark · Diagram labelled with N, S, coil, and rotation arrow
B1 (b) · 1 mark · States that as the coil rotates faster, more field lines are cut per second/greater voltage induced.
A1 (b) · 1 mark · Links greater speed to increased induced voltage.
Worked solution
b. Rotating the coil faster means more magnetic field lines are cut each second, so a greater voltage is induced in the coil.