Question

A frame $\text{PQRS}$ is placed in a region where magnetic field $B$ is present, as shown in the figure. A rod of length $2\text{m}$ moves with a constant velocity $25\text{m/s}$ and the strength of the magnetic field inside the plane of paper is $0.1\text{T}$. If the resistance of the rod is $10\Omega$ and the resistance of the frame is negligible, then calculate the power spent in this process

• A. $5\text{W}$
• B. $2.5\text{W}$
• C. $1.5\text{W}$
• D. $1\text{W}$

Answer 1

The correct option is B $2.5\text{W}$

Emf induced across the rod,

$E=Bvl$

$\therefore$ Power generated in the circuit,

$P=\frac{E^2}{R}=\frac{(Bvl{)}^2}{R}$

$=\frac{(0.1\times 25\times 2{)}^2}{10}=2.5\text{W}$

Hence, $\left(\text{B}\right)$ is the correct answer.