Question

What is the value of shunt which passes $10\%$ of the main current through a galvanometer of $99\Omega$ ?

• A. $25\Omega$
• B. $50\Omega$
• C. $11\Omega$
• D. $15\Omega$

Answer 1

The correct option is C $11\Omega$

Given:
$G=99\Omega$

Let $I$ be the current passes through main circuit.

$\therefore I_g=\left(\frac{10}{100}\right)I=0.1I$

Now using formula,

$S=\frac{I_{g}G}{(I-I_g)}$

$\Rightarrow S=\frac{0.1I\times 99}{(I-0.1I)}=\frac{0.1}{0.9}\times 99$

$\therefore S=11\Omega$

Hence, option $\left(c\right)$ is correct.

Key concept: Voltage across shunt and galvanometer are same.