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Oscilloscope practice

Read voltage amplitude, peak-to-peak voltage, period, frequency and phase difference.

Practise

Phase difference

The traces have the same frequency. Find the magnitude of their phase difference in degrees, using corresponding rising zero crossings. Give your answer to 3 significant figures.

Ideal sinusoidal voltage traces; one large square is one division. A is solid and B, when present, is dashed. Both channels have the same sensitivity and time-base.

Trace A has amplitude 2.5 divisions and period 2 divisions. Vertical sensitivity 1 V/div; time-base 0.1 ms/div. Trace B is shifted right by 0.25 divisions and lags A.A solid · B dashed1 V/div · 0.1 ms/div0 V
One large square is one division; the middle horizontal line is 0 V.
Diagram text alternative

Trace A has amplitude 2.5 divisions and period 2 divisions. Vertical sensitivity 1 V/div; time-base 0.1 ms/div. Trace B is shifted right by 0.25 divisions and lags A.

Larger diagram
Trace A has amplitude 2.5 divisions and period 2 divisions. Vertical sensitivity 1 V/div; time-base 0.1 ms/div. Trace B is shifted right by 0.25 divisions and lags A.A solid · B dashed1 V/div · 0.1 ms/div0 V

Treat the given values as exact unless an uncertainty is stated.

Use decimals or e notation, e.g. 4.2e-3. Enter the unit separately.

Hint

Phase magnitude = horizontal shift / one-cycle span × 360°. Trace B is shifted right and lags A.

Worked solution
  1. Shift = 0.25 divisions; cycle = 2 divisions.
  2. Phase difference = 0.25/2 × 360° = 45°. B lags A.
  3. Answer: 45.0 ° (3 significant figures).
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Question type: Mixed practice
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Voltage and time scales

Multiply vertical divisions by volts per division. Amplitude runs from the zero line to a peak; peak-to-peak spans both extremes. Multiply horizontal divisions for one complete cycle by the time-base. Convert ms to s before using f = 1/T.

Phase difference

For traces of the same frequency, use corresponding rising zero crossings or matching peaks. Phase magnitude = horizontal shift / period span × 360°. The dashed trace B is shifted right and lags A here. A half-cycle shift is 180°; at that limit leading and lagging are equivalent descriptions.

These are ideal sinusoidal signals with a shared sensitivity and time-base. Triggering, probe attenuation, offsets, noise and rms voltage are outside these tasks.

A-level relevance

AQA 7408: 7.1 AT h (selected); AQA 7408: 3.3.1.1 (selected); OCR A H556: 1.2.2(h); 4.4.1(b–c) (selected). Tasks cover the selected skills listed above.

AQA specification · AQA specification · OCR A specification · AQA practical handbook · OCR practical skills handbook

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