Discussion Forum

The deflection  in  galvanometer falls to $\left(\frac{1}{4}\right)^{th}$  when it is shunted by 3 $\Omega$ .If additional shunt of 2 $\Omega$ is connected to earlier shunt in parallel, the deflection in galvanometer falls to 

Answer:

Explanation:

 In galvanometer,

  $\frac{l_{g}}{l}=\frac{S}{S+G}$

 where, S is shunt resistance, G is resistance of galvanometer

$\Rightarrow$   $\frac{1}{4}=\frac{3}{3+G}$

 or  G= 9 $\Omega$

 in new condition, 

$\Rightarrow\frac{l_{g}}{l}=\frac{\frac{6}{5}}{\frac{6}{5}+9}$

 [ Effective shunt resistance = $\frac{3\times2}{3+2}=\frac{6}{5}\Omega$]

 = $\left(\frac{1}{8.5}\right)^{th}$