Question

$100\text{mA}$ current gives a full scale deflection in a galvanometer of $2\Omega$ resistance. The resistance connected with the galvanometer to convert it into a voltmeter to measure $5\text{V}$ is

• A. $98\Omega$
• B. $52\Omega$
• C. $50\Omega$
• D. $48\Omega$

Answer 1

The correct option is D $48\Omega$

Given:
$I_g=100\text{mA};G=2\Omega ;V=5\text{V}$


Now,

$V=I_g(G+R)$

$5=100\times {10}^{-3}(2+R)$

$\Rightarrow 50=2+R$

$\therefore R=48\Omega$

Hence, option $\left(D\right)$ is the correct answer.

Why this question ? Concept: To convert a galvanometer into a voltmeter, resistance is connected in series with it.