A contactless switch contains a control coil next to a detector coil. Neither coil moves. Changing the current in the control coil changes the magnetic field through the detector coil.
The table shows two tests. The total change in the magnetic field through each turn of the detector coil has the same magnitude in both tests. In both tests, the magnetic field changes at a constant rate throughout the stated time interval.
| Test | Change in magnetic field | Number of turns on detector coil | Time taken for field change | Peak potential difference |
|---|---|---|---|---|
| 1 | grows from zero to a fixed value | 200 | 8.0 ms | +0.15 V |
| 2 | collapses from the same value to zero | 500 | 2.0 ms | to be determined |
Calculate the magnitude of the peak potential difference in test 2.
Explain whether the peak potential difference in test 2 is positive or negative.
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.