Q 12-04-068JEE MainJEE Main 2024 (1 Feb, Shift 2)Easy
A moving coil galvanometer has 100 turns and each turn has an area of $2.0\ \text{cm}^2$. The magnetic field produced by the magnet is $0.01\ \text{T}$ and the deflection in the coil is $0.05$ radian when a current of $10\ \text{mA}$ is passed through it. The torsional constant of the suspension wire is $x\times10^{-5}\ \text{N m rad}^{-1}$. The value of $x$ is ______.
Numerical value type. Enter your answer.
Answer: 4
In equilibrium $NIAB = k\theta$:
$$k = \frac{100\times10\times10^{-3}\times2\times10^{-4}\times0.01}{0.05} = \frac{2\times10^{-6}}{0.05} = 4\times10^{-5}\ \text{N m rad}^{-1}$$
Solution by Sreeraj P, M.Sc Physics