Question

To send $10\%$ of main current through a moving coil galvanometer of resistance $99\Omega$, shunt required is?

• A. $9\Omega$
• B. $11\Omega$
• C. $10\Omega$
• D. $9.9\Omega$

Answer 1

The correct option is B $11\Omega$

Given:

The resistance of the galvanometer is $R=99\Omega$.

The current through the galvanometer is 10% of the main current.

So, the current through the galvanometer is given by:

$I=I_g(1+\frac{r_g}{S})$

$I$ is the total current i.e. $100i$ whereas $I_g$ is the current through galvanometer i.e. $10\%$ or $10i$.

$100i=10i(1+\frac{99}{S})$

$S=\frac{99}{9}⟹11\Omega$