Induction between two coils is the most common Question 1 family in Paper 5. Here coil P is driven by a signal generator and you measure the peak e.m.f. E induced in coil Q as the frequency f changes. Watch the set-up built step by step, with the variables and the graph beside it, then build it yourself and check it against the mark points.
Past-paper referenceOriginal experiment, wording and figures, written in the style of Cambridge AS & A Level Physics 9702 Paper 5, Question 1. It is not copied from a past paper. The “what the examiners said” notes are our paraphrase of the Principal Examiner Reports for Teachers.
Practise next: 9702/52 May/June 2023, Question 1 (e.m.f. induced in coil Q as the resistance in series with coil P changes) · official past papers
Practise next: 9702/53 October/November 2023, Question 1 (e.m.f. induced as the frequency changes, with a log graph) · official past papers
Practise next: 9702/52 October/November 2017, Question 1 (e.m.f. induced as the separation of the coils changes) · official past papers
Examiner reports used: 9702 June 2017, June 2023, November 2023 and March 2024.
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What a full-mark diagram shows
The coil P circuit
A signal generator (an a.c. supply whose frequency can change) and a c.r.o. connected across coil P. Never a d.c. battery.
The coil Q circuit
A separate circuit: only a c.r.o. or a.c. voltmeter across coil Q. No supply, no short-circuiting lead.
Fixed separation
Both coils clamped on a common axis, with a rule to set x and keep it the same.
Using the c.r.o.
f from the length of one wave × time-base, then f = 1/T. E from the height of a peak × y-gain.
Habits the examiner reports keep asking for
Say which p.d. is kept constant, and how: adjust the signal generator output until the trace across coil P is the same height.
“The number of turns on both coils”, not “the number of coils” or one coil only.
Explain the c.r.o. readings: time-base for the period, y-gain for the peak value.
Additional detail must be a method: an iron core or a larger V to increase E, not just “to reduce the uncertainty”.
Safety in this experiment is about hot coils. Switch off between readings.