Question

The sensitivity of a galvanometer is $60div/A$. When a shunt is used, its sensitivity becomes $10div/A$. If the galvanometer is of resistance $20\Omega$, the value of shunt used is:

• A. $4\Omega$
• B. $5\Omega$
• C. $20\Omega$
• D. $2\Omega$

Answer 1

The correct option is A $4\Omega$

The sensitivity of the galvanometer can be given as:

$\frac{i_g}{i}=\frac{S}{S+G}$

Given that: $\frac{i_g}{i}=\frac{10}{60}=\frac{1}{6}$ and $G=20\Omega$

$\Rightarrow \frac{1}{6}=\frac{S}{S+20}$

$\Rightarrow S=4\Omega$