Physics 9702 · AS & A Level · Electromagnetic induction
Electromagnetic induction — practice question
A substantial aluminium disc has radius $0.36\,\text{m}$. It turns together with the wheels of a vehicle and is part of an electromagnetic braking system on the vehicle. To switch on the braking system, a uniform magnetic field of flux density $0.17\,\text{T}$ is activated. This magnetic field is at right angles to the plane of rotation of the disc, as shown in Fig. 6.1.
(a(i))[2]
Define the term magnetic flux.
(a(ii))[2]
Calculate the magnetic flux linked with the disc. Include a unit in your answer.
(b)[3]
The disc is turning at $25$ revolutions per second. Calculate the magnitude of the electromotive force (e.m.f.) induced between the axle and the rim of the disc.
(c)[3]
The axle and the rim are connected to an external circuit so that the rotational energy of the disc can be stored for later use. The direction of rotation is shown in Fig. 6.1. Use Lenz’s law of electromagnetic induction to decide whether the current in the disc is from the rim to the axle or from the axle to the rim. Explain your reasoning.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “magnetic flux density multiplied by area” …