Magnetic fields — AS & A Level Physics (9702) questions by topic
Magnetic fields questions carry heavier weighting than most A Level Physics topics, from 8 to 14 marks, covering flux density definitions, Hall probe geometry, electromagnetic braking on a rotating disc, and field lines around a current-carrying wire.
Draw and calculate feature among the top command words, alongside state, explain and deduce: draw concentric field lines with the correct spacing and direction, then calculate force per unit length or induced current. 13 real questions from 2023 to 2025 papers sit on this page. Submitting each attempt for instant marking catches a missing unit on flux density or a muddled Lenz's-law direction straight away, rather than after a full mark scheme readthrough.
What examiners look for
- A recurring criticism is candidates adding a second, contradictory definition after an otherwise correct one, or defining flux as a dimensionless number of lines.
- Examiners note many calculate flux density correctly but omit its unit, and some believe one significant figure is sufficient.
- Reports describe confusion between the external field and the field of an induced current, or forces and currents wrongly said to oppose motion directly rather than via a force.
- A common mistake is describing the force on a charged particle without specifying that the particle must be moving.
- Strong answers correctly draw concentric field lines with credit for both shape and direction, and calculate force per unit length accurately.
May–June 2025, Paper 41
May–June 2025, Paper 43
May–June 2025, Paper 44
A rectangular coil PQRS of wire is free to rotate about its axis XY. The coil has length QR of 5.4 cm, width PQ of 2.5 cm and has 190 turns of wire. The plane of the coil is at an…
Answer this question and get it marked →May–June 2024, Paper 42
State Faraday's law of electromagnetic induction.
Answer this question and get it marked →October–November 2024, Paper 41
October–November 2024, Paper 43
February–March 2023, Paper 42
A Hall probe is placed in a magnetic field. The Hall voltage is zero. The Hall probe is rotated to a new position in the magnetic field. The Hall voltage is now maximum. Explain…
Answer this question and get it marked →May–June 2023, Paper 41
State what is meant by a magnetic field.
Answer this question and get it marked →May–June 2023, Paper 42
A heavy aluminium disc has a radius of 0.36 m. The disc rotates with the wheels of a vehicle and forms part of an electromagnetic braking system on the vehicle. In order to…
Answer this question and get it marked →May–June 2023, Paper 43
State what is meant by a magnetic field.
Answer this question and get it marked →October–November 2023, Paper 41
October–November 2023, Paper 42
A Hall probe containing a thin slice of semiconducting material is placed in a uniform magnetic field of flux density B. The largest faces of the slice are perpendicular to the…
Answer this question and get it marked →October–November 2023, Paper 43
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