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

Answer 1

Answer: (D)

$G=\left(\frac{GS}{G+S}\right)+S^{\prime }$
$G-\frac{GS}{G+S}=S^{\prime }$
$\therefore S^{\prime }=\frac{G^2}{G+S}$