A speed detector has a coil fixed to a trolley and a bar magnet clamped beside the track. The coil is connected to a centre-zero meter. With the north pole of the magnet facing the coil, the trolley runs towards the magnet and the meter pointer moves to the right.
Which change makes the pointer move the same distance to the left the next time the trolley runs towards the magnet?
Use a stronger magnet with its north pole facing the coil.
Turn the magnet round and run the trolley at twice the speed.
Run the trolley towards the magnet at half the speed.
Turn the magnet so that its south pole faces the coil.
92 exam-style questions on Edexcel GCSE Physics 13.1 Inducing a current, covering 13.1.1 Producing an electric current by induction, 13.1.2 Factors affecting the induced potential difference, 13.1.3 Alternators and dynamos, and 13.1.4 Microphones and loudspeakers. Each one has a worked solution and a mark scheme showing where the marks go.