Question

If a shunt of value $\frac{1}{n}$ times the galvanometer resistance, is applied to a moving coil galvanometer. By which factor its current sensitivity will change?

• A. $\frac{1}{n}$
• B. $\frac{1}{n-1}$
  
• C. $\frac{1}{n+1}$
  
• D. $\frac{n}{n+1}$

Answer 1

The correct option is C $\frac{1}{n+1}$


MCG without shunt :
$C{S}_1=\frac{{\theta }_1}{I_g}$

MCG with shunt :
$S=\frac{G}{n}$
$C{S}_2=\frac{{\theta }_2}{I}=\frac{{\theta }_2}{(n+1)I_g}$

$I_g$ is the maximum current that galvanometer can allow to pass.
So, ${\theta }_1={\theta }_2$

$\therefore \frac{C{S}_2}{C{S}_1}=\frac{1}{n+1}$