question_answer

In the following figure, the magnet is moved towards the coil with a speed v and induced emf is e. If magnet and coil recede away from one another each moving with speed v, the induced emf in the coil will be

A)            e

B)            2e

C)            e/2

D)            4e

Correct Answer: B

Solution :

                   \[{{\left( \frac{d\varphi }{dt} \right)}_{\text{In first case}}}=e\]                    \[{{\left( \frac{d\varphi }{dt} \right)}_{\text{relative velocity}2v}}=2{{\left( \frac{d\varphi }{dt} \right)}_{\text{I case}}}=2e\]