Q 12-04-079JEE MainJEE Main 2024 (6 Apr, Shift 1)Easy
A circular coil having 200 turns, $2.5\times10^{-4}\ \text{m}^2$ area and carrying $100\ \mu\text{A}$ current is placed in a uniform magnetic field of $1\ \text{T}$. Initially the magnetic dipole moment $(\vec M)$ was directed along $\vec B$. The amount of work required to rotate the coil through $90^\circ$ from its initial orientation such that $\vec M$ becomes perpendicular to $\vec B$ is ______ $\mu\text{J}$.
Numerical value type. Enter your answer.
Answer: 5
$M = NIA = 200\times100\times10^{-6}\times2.5\times10^{-4} = 5\times10^{-6}\ \text{A m}^2$.
$$W = MB(\cos0^\circ - \cos90^\circ) = 5\times10^{-6}\times1 = 5\ \mu\text{J}$$
Solution by Sreeraj P, M.Sc Physics