OCR A Gateway Physics Higher tier directly examines reading values off an oscilloscope screen — a skill AQA mentions only as a practical tool, without examining the reading itself in structured questions.
- Time-base setting — shown in ms/division (or similar), this tells you how much time one square (division) across the screen represents. Count the number of divisions for one complete wave cycle and multiply by the time-base to find the period T, then use f = 1/T to find frequency.
- Peak-to-peak voltage — the vertical distance from the top of the wave to the bottom, not from the centre line to the top. Read the number of divisions and multiply by the volts/division setting. Peak-to-peak voltage is double the peak voltage (Vpp = 2 × Vpeak) for a symmetrical AC signal.
- Comparing AC and DC traces — an AC trace is a repeating wave (sine wave) that crosses above and below the centre line; a DC trace is a flat horizontal line, since direct current does not vary with time.
Quick Check: An oscilloscope's time-base is set to 5 ms/division. One complete wave takes up 4 divisions on the screen. Calculate the frequency of the signal.
T = 4 × 5 ms = 20 ms = 0.02 s. f = 1/T = 1/0.02 = 50 Hz.
This higher tier covers OCR A (J249) Higher Only: Reading an Oscilloscope Trace within Mains Electricity & Safety for GCSE Physics. Revise Mains Electricity & Safety in Electricity for GCSE Physics with 18 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 14 of 17 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.