A machine uses a stationary coil connected to a data logger to monitor a rotating shaft. Four identical permanent magnets are fixed at equal intervals around the shaft. Each magnet passes close to the coil once during each rotation and produces one voltage pulse.
The machine is tested before and after an adjustment. The coil, magnets and distance between the magnets and the coil are unchanged.
| test | number of pulses in 0.50 s | mean peak potential difference | mean duration of each pulse |
|---|---|---|---|
| before adjustment | 20 | 0.16 V | 15 ms |
| after adjustment | 30 | 0.24 V | 10 ms |
Explain why the data logger records a potential difference as a magnet passes the coil.
A technician concludes that the shaft rotates 1.5 times as fast after the adjustment.
Explain whether all the measurements support this conclusion.
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.