Question 276: Magnetism and Matter

Question

A moving coil galvanometer has 100 turns and each turn has an area of $2.0 \mathrm{~cm}^2$. The magnetic field produced by the magnet is $0.01 \mathrm{~T}$ and the deflection in the coil is 0.05 radian when a current of $10 \mathrm{~mA}$ is passed through it. The torsional constant of the suspension wire is $x 	imes 10^{-5} \mathrm{~N}-\mathrm{m} / \mathrm{rad}$. The value of $x$ is _______ .

Accepted Answer

$\begin{aligned} & 	au=	ext { BINAsin } \phi \\ & \mathrm{C} 	heta=	ext { BINAsin } 90^{\circ} \\ & \mathrm{C}=\frac{\mathrm{BINA}}{	heta}=\frac{0.01 	imes 10 	imes 10^{-3} 	imes 100 	imes 2 	imes 10^{-4}}{0.05} \\ & =4 	imes 10^{-5} \mathrm{~N}-\mathrm{m} / \mathrm{rad} . \\ & \mathrm{x}=4\end{aligned}$

Magnetism and Matter

Choose the correct answer: