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 sped 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

Answer: (B)

$2Blv$

Answer 2

Two emf's induces in the closed circuit each of value $Blv$. These two emf's are additive. So $E_{\text{net}} = 2Blv$