Question

A rod $PQ$ of length $1\text{m}$ is placed on the frame $CDEF$. This setup is placed in a space where a uniform magnetic field $\overrightarrow{B}$, of magnitude $1\text{T}$ exist. The rod moves with a constant velocity of $20\text{m/s}$. The power spent by external force to keep the rod moving with constant velocity is -

Given, $R=0.2\Omega$ and all other wires and rod have zero resistance.

• A. $1\text{kW}$
• B. $2\text{kW}$
• C. $3\text{kW}$
• D. $4\text{kW}$

Answer 1

The correct option is B $2\text{kW}$

We know that the power is given by,

$P=\frac{E^2}{R}=\frac{B^2{l}^2{v}^2}{R}$

$\Rightarrow P=\frac{1^2\times 1^2\times {20}^2}{0.2}=2\text{kW}$

Hence, option $\left(B\right)$ is the correct answer.