A greenhouse irrigation controller contains a low-voltage power supply. A technician tests the supply using the same primary and secondary coils in two arrangements. In one arrangement, both coils are wound around an iron core. In the other arrangement, both coils are wound around a rigid plastic former of the same shape. The same alternating current is passed through each primary coil. A voltmeter connected across the secondary coil gives a much larger reading when the iron core is used.
Explain why the voltmeter reading is much larger when the iron core is used.
The iron core is refitted and the alternating supply is replaced by a cell. After the current has become steady, the connections to the cell are reversed. The voltmeter gives a reading briefly. Give the reason why.
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.