One conducing U tube can be 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 ........

Options

A. zero
B. 2Blv
C. Blv
D. `-Blv`

Answer

B

Explanation

Induced emf due to bothh tubes ,
`epsilon=Bvl + Bvl`
`therefore epsilon` =2Bvl (both batteries tubes considered as in series )