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)

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