A rowing machine uses its flywheel to turn the coil of an alternator at a steady speed. In a first test, the output potential difference is zero at the moment when the sides of the coil are moving horizontally and the magnetic field lines are also horizontal. For a second test, the magnet is turned through 90° so that its field lines are vertical, and the coil turns at the same speed. At the same coil position, the output potential difference is no longer zero. Which statement explains why?
The moving sides of the coil now cut across magnetic field lines.
Turning the magnet has reversed the field, so the output polarity has reversed.
Turning the magnet has made the magnetic field around the coil sides stronger.
The moving sides of the coil now move along the magnetic field lines.
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.