The sensitivity of a galvanometer is 60 division/A. When a shunt is used, its sensitivity becomes 10…
The sensitivity of a galvanometer is 60 division/A. When a shunt is used, its sensitivity becomes 10 division/A. If the galvanometer is of resistance $20 \Omega$, the value of shunt used is
$4 \Omega$
$5 \Omega$
$20 \Omega$
$2 \Omega$
Solution
We have, $i_g=i\left(\frac{S}{G+S}\right)$
where $i=$ total current
Sensitivity $=\frac{i_g}{i}=\frac{10}{60}=\frac{1}{6}$
$\therefore \quad \frac{1}{6}=\frac{S}{G+S}$
$\begin{array}{ll}\Rightarrow & G+S=6 S \\ \Rightarrow & G=5 S \text { or } S=\frac{G}{5} \\ \Rightarrow & S=\frac{20}{5}=4 \Omega(\because G=20 \Omega)\end{array}$