Q 12-06-068JEE MainJEE Main 2023 (24 Jan, Shift 1)Easy
A conducting loop of radius $\dfrac{10}{\sqrt\pi}\ \text{cm}$ is placed perpendicular to a uniform magnetic field of $0.5\ \text{T}$. The magnetic field is decreased to zero in $0.5\ \text{s}$ at a steady rate. The induced emf in the circular loop at $0.25\ \text{s}$ is
Answer: (B) $\text{emf}=10\ \text{mV}$
Area $A=\pi\left(\dfrac{0.1}{\sqrt\pi}\right)^2=0.01\ \text{m}^2$. The field falls steadily, so the emf is constant:
$$\varepsilon=A\frac{\Delta B}{\Delta t}=0.01\times\frac{0.5}{0.5}=0.01\ \text{V}=10\ \text{mV}$$
Solution by Sreeraj P, M.Sc Physics