Question

At $t=0$, when the magnetic field is switched on, the conducting rod is moved to the left at a constant speed of $5cm$ $s^{-1}$ by some external means. The magnitude of the force required to move the conducting rod at a constant speed of $5cm$ $s^{-1}$ at the same instant $t=2s$ is equal to

• A. $0.16N$
• B. $0.12N$
• C. $0.08N$
• D. $0.06N$

Answer 1

The correct option is C $0.08N$

Emf induced across the rod $=Bvl$

Thus current in the circuit $=\frac{Bvl}{R}$

Force acting on the rod $=Bil=\frac{B^{2}v{l}^2}{R}$$=\frac{2^2\times 0.05\times {0.2}^2}{1}N=0.08N$