question_answer

One conducting 17-tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed v, then the emf induced in the circuit in terms of B, 1 and v, where 1 is the width of each tube, will be                                      [AIEEE 2005]

A) \[BIl\]

B) \[-BIl\]

C) zero

D) \[2\,BIl\]

Correct Answer: D

Solution :

[d] Relative velocity of tubes with respct to each other

Now, emf induced in circuit made by two tubes is