Question

A galvanometer of resistance, $G$ is shunted by a resistance $S$ $ohm$. To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is

• A. $\frac{S^2}{(S+G)}$
• B. $\frac{SG}{(S+G)}$
• C. $\frac{G^2}{(S+G)}$
• D. $\frac{G}{(S+G)}$

Answer 1

The correct option is C $\frac{G^2}{(S+G)}$

If resistance remains same so current will be unchanged.
$G=\frac{GS}{G+S}+R\Rightarrow R=G-\frac{GS}{G+S}$
or, $R=\frac{G^2}{G+S}$