Question

The deflection in a moving coil galvanometer falls from $50$ divisions to $10$ divisions when a shunt of $20\Omega$ is connected with it. The resistance of galvanometer coil is?

• A. $48\Omega$
• B. $50\Omega$
• C. $52\Omega$
• D. $30\Omega$

Answer 1

The correct option is A $48\Omega$

Here let the value of current from one division be $i$ A.

Thus the current through ammeter $I=50i$ and through Galvanometer $I_g=10i$

$S=\frac{I_g}{I-I_g}G$

$\Rightarrow G=\frac{I-I_g}{I_g}S$

$=\frac{50i-10i}{10i}\times 12\Omega$

$=4\times 12\Omega$

$=48\Omega$