Physics 9702 · AS & A Level · Electromagnetic induction

Electromagnetic induction — practice question

(a)[2]

State Faraday’s law for electromagnetic induction.

(b)

A metal rod is given uniform acceleration from rest in a uniform magnetic field, as shown in Fig. 7.1. The rod has length $l$ and the magnetic flux density of the magnetic field is $B$. An electromotive force (e.m.f.) is induced in the rod. Fig. 7.2 shows how the induced e.m.f. $E$ varies with time $t$.

(b(i))[2]

Explain how Fig. 7.2 indicates that $E$ is proportional to the rod’s velocity $v$.

(b(ii))[3]

Use Faraday’s law to demonstrate that the time dependence of $E$ is $E = Blat$, where $a$ denotes the rod’s acceleration.

(b(iii))[2]

The rod’s length is $0.45\,\text{m}$. Its acceleration $a$ is $7.8\,\text{m s}^{-2}$. Determine the value of $B$.

(ii)[3]

Use Faraday’s law to show that the time variation of $E$ is $E = Blat$, where $a$ is the rod’s acceleration.

(iii)[2]

The rod’s length is $0.45\,\text{m}$. Its acceleration $a$ is $7.8\,\text{m s}^{-2}$. Determine the value of $B$.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: Induced e.m.f. is proportional to the rate of change of magnetic flux linkage

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