Question

A galvanometer having internal resistance $10\Omega$ requires $0.01A$ for a full scale deflection. To convert this galvanometer to a voltmeter of full-scale deflection at $120V$, we need to connect a resistance of:

• A. $11990\Omega$ in series
• B. $11990\Omega$ in parallel
• C. $12010\Omega$ in series
• D. $12010\Omega$ in parallel

Answer 1

Answer: (A)

$11990\Omega$ in series

Given : $G=10\Omega$ $I_G=0.01A$ $V=120$ volt

Let the resistance to be connected in series be $R$

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

$120=0.01(10+R)$

$⟹$ $R=11990$ $\Omega$