AQA and OCR B ask you to draw and interpret graphs of potential difference against time for an alternating supply, such as the output of a generator.
- Period: read the time for one complete wave from the time axis. Then use f = 1/T to find the frequency.
- Peak potential difference: the height of the wave above the centre line, read from the potential difference axis.
- Comparing AC and DC graphs: an AC graph is a repeating wave that crosses above and below the centre line; a DC graph is a flat horizontal line, since direct current does not change direction.
Quick Check: On a graph of potential difference against time, one complete wave takes 20 ms. Calculate the frequency of the supply.
T = 20 ms = 0.02 s. f = 1/T = 1/0.02 = 50 Hz.
This higher tier covers Higher Tier: Reading a Potential Difference-Time Graph within Mains Electricity & Safety for GCSE Physics. Revise Mains Electricity & Safety in Electricity for GCSE Physics with 17 exam-style questions and 30 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 13 of 16 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
Practice questions for Mains Electricity & Safety
What does AC stand for, and how does it differ from DC?
Explain how a fuse protects an electrical circuit from damage.