Question

The full scale deflection current of a galvanometer of resistance $1\Omega$ is 5 mA. How will you convert it into a voltmeter of range 5 V ?

• A. $999\Omega$
• B. $99\Omega$
• C. $9\Omega$
• D. $989\Omega$

Answer 1

The correct option is A $999\Omega$

Given : $I=0.005$ A $G=1$ $\Omega$

Potential difference between A and B, $V=5$ volts

$\therefore$ $V=I(G+R)$

$\therefore$ $5=0.005(1+R)$ $⟹R=999\Omega$

Thus a galvanometer is converted into a voltmeter by connecting it to a series resistance of $999\Omega$.