Question

The coil in a MCG has an area of 4 $c{m}^2$ and 500 turns. The intensity of magnetic induction is 2T. When a current of ${10}^{-4}$ A is passed through it, the deflection is ${20}^0$ . The couple per unit twist is (N-m)

• A. $3\times {10}^{-6}$
• B. $2\times {10}^{-6}$
• C. $4\times {10}^{-6}$
• D. $5\times {10}^{-6}$

Answer 1

Answer: (B)

$2\times {10}^{-6}$

Given that,
$A=4c{m}^2=4\times {10}^{-4}{m}^2$
N = 500
B = 2T
$I=!0^{-4}A$
$\theta ={20}^{\circ }$
For moving coil galvanometer, we have
$NBIA=C\theta$
$C=\frac{NBIA}{\theta }$
$C=\frac{\left(500\right)\left(2\right)(4\times {10}^{-4})\left({10}^{-4}\right)}{20}$
$C=\frac{4000\times {10}^{-8}}{20}=2\times {10}^{-6}Nm$