Question

When shunt of $4\Omega$ is attached to a galvanometer, the deflection in the galvanometer is reduced to $\frac{1}{5}th$ . If an additional shunt of $2\Omega$ is also connected. The deflection of galvanometer will be reduced to

• A. $\frac{1}{10}th$ of initial
• B. $\frac{1}{13}\text{th}$ of initial
• C. remains the same
• D. none of these

Answer 1

Answer: (B)

Intial condition

When shunt of $4\Omega$ is used, $\frac{i}{5}\times G=\frac{4}{5}i\times 4$

$\Rightarrow G=16\Omega$
When additional shunt of $2\Omega$ is attached,
$i^{{}^{\prime }}\times 16=\left(i-i^{{}^{\prime }}\right)\frac{4}{3}$
$12i^{{}^{\prime }}=i-i^{{}^{\prime }}$
$\Rightarrow i^{\prime }=\frac{1}{13}$

It will reduce to $\frac{1}{13}$ of the initial value.