The current in a mains heater completes 50 full cycles each second. In each cycle, charge moves in one direction and then in the opposite direction.
How many full cycles occur in 3.0 s, and how many times does the current reverse direction during each full cycle?
150150150 full cycles; one reversal per cycle.
300300300 full cycles; two reversals per cycle.
300300300 full cycles; one reversal per cycle.
150150150 full cycles; two reversals per cycle.
81 exam-style questions on Edexcel GCSE Physics 10.4 Mains electricity, covering 10.4.1 Direct and alternating current, 10.4.2 Live, neutral and earth wires; safety, 10.4.3 Mains wire potential differences and dangers, and 10.4.4 Power ratings and energy use. Each one has a worked solution and a mark scheme showing where the marks go.