A supply produces the repeating voltage pattern shown in the table. Between the listed values, the voltage changes smoothly.
| Time in ms\mathrm{ms}ms | Voltage in V\mathrm{V}V |
|---|---|
| 0 | 0 |
| 5 | +12 |
| 10 | 0 |
| 15 | -12 |
| 20 | 0 |
| 25 | +12 |
A resistor is connected to this supply. Which statement is correct?
The current is direct because its value repeats every 20 ms20\ \mathrm{ms}20 ms.
The current is alternating because its value reaches zero every 10 ms10\ \mathrm{ms}10 ms.
The current is alternating because its direction reverses every 10 ms10\ \mathrm{ms}10 ms.
The current is direct because its direction reverses every 20 ms20\ \mathrm{ms}20 ms.
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.