Question

One conducting U 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, l and v where l is the width of each tube, will be

(a) zero 

(b) 2Blv 

(c) Blv 

(d) –Blv

Answer 1

(a) : The emf induced in the circuit is zero because the two emf induced are equal and opposite when one U tube slides inside another tube.