(a)[3]
On Fig. 10.2, sketch a graph showing how the induced electromotive force (e.m.f.) changes with time during one revolution of the coil. Mark on the time axis the points where the coil has turned through $1/4$ revolution and $3/4$ revolution.
(b)[1]
Explain why an e.m.f. is produced only when the coil is rotating.
(c)[2]
State the names of the components labelled P and Q and state their purpose.
(d)[2]
State two changes that would lead to a larger e.m.f. being induced.