A technician tests a transformer using a control unit connected to the primary coil. The primary and secondary coils are separate and are wound on the same iron core.
During each interval, the current changes steadily from the value at the beginning to the value at the end.
| Interval | Current at beginning of interval in A | Current at end of interval in A |
|---|---|---|
| P | +1.5 | +1.5 |
| Q | +1.5 | -1.5 |
| R | -1.5 | -1.5 |
| S | -1.5 | +1.5 |
Explain why a potential difference is induced across the secondary coil during intervals Q and S, but not during intervals P and R.
The potential difference recorded during interval Q has positive polarity. Give the polarity of the potential difference during interval S.
96 exam-style questions on AQA GCSE Physics 7.3 Induced potential, transformers and the National Grid (HT only), covering 7.3.1 Induced potential (HT only), 7.3.2 Uses of the generator effect (HT only), 7.3.3 Microphones (HT only), and 7.3.4 Transformers (HT only). Each one has a worked solution and a mark scheme showing where the marks go.