2025 · M/J · 5054/22 | Q7

0/46parts marked · 0 of 80 marks

Question (7 of 9)11 marks · Practise this topic →

Options

Theory: answer all nine questions. Show working and units. For drawings or plotted graphs, upload a clear photo of your sketch on the supplied figure.

Fig. 7.1 shows a simple d.c. motor. The poles at the ends of the magnets are not labelled.

(a)State the purpose of the split-ring commutator and the brushes.

Fig. 7.1 — see the question text for what it shows

Answer guidance

State A short answer. No explanation is needed, and adding one cannot earn extra marks.

[3 marks]

There is an upward force shown on the left side of the coil.

There is a magnetic field in the space between the ends of the magnets.

State the direction of this magnetic field.

(b)Explain how you determined this direction.

Answer guidance

Explain Give reasons, not just what happens. Each distinct reason is usually worth a mark.

[3 marks]

(c)State what happens to the rotation of the coil if the magnetic field and the current in the coil are both reversed at the same time.

Answer guidance

State A short answer. No explanation is needed, and adding one cannot earn extra marks.

[1 mark]

In Fig. 7.1, the coil is horizontal. The force upward on the left side and the force downward on the right side are each 2.3 N.

The distance between the sides of the coil and the axis is 0.15 m.

Calculate the total moment exerted on the coil by these forces.

(d)(i)Give the unit of your answer.

Answer guidance

Calculate Show your working. The method can earn marks even when the final value is wrong, and a bare answer often cannot.

[3 marks]

(d)(ii)Explain why the turning effect becomes smaller as the coil becomes more vertical.

Answer guidance

Explain Give reasons, not just what happens. Each distinct reason is usually worth a mark.

[1 mark]

5054/22/M/J/25Cambridge O Level Physics 5054 · May/June 2025 · Paper 2 variant 2 · Question 7