Question

The deflection in a moving coil galvanometer falls from $50$ divisions to $10$ division , when a shunt of $12\Omega$ is applied, The resistance of the galvanometer is

• A. $12\Omega$
• B. $24\Omega$
• C. $36\Omega$
• D. $48\Omega$

Answer 1

The correct option is D $48\Omega$

In a moving coil galvanometer, $I\propto \theta$

Thus, $\frac{Ig}{I}=\frac{10}{50}=\frac{1}{5}$

$\Rightarrow I=5I_g$

Since the potential difference across the galvanometer and shunt resistance are same we can say that, $S{I}_s=I_{g}G$


$\therefore S[I-I_g]=G{I}_g$

From the data obtained,

$12[5I_g-I_g]=G{I}_g$

$G=4\times 12=48\Omega$

Hence, option (d) is the correct answer.