Question

The resistance of a moving coil galvanometer is $20 \, \Omega$ . It requires $0.01A$ current for full-scale deflection. The value of resistance to convert it into a voltmeter of the range $20 \, V$ will be

• A. $198 \, \Omega$
• B. $1980 \, \Omega$
• C. $20 \, \Omega$
• D. $0 \, \Omega$

Answer 1

Answer: (B)

$V_{G}=I_{G}G$
$V_{G}=0.01\times 20=0.2 \, V$
$R=\left(\frac{V}{V_{G}} - 1\right)G$
$R=\left(\frac{20}{0.2} - 1\right)\left(20\right)=1980 \, \Omega$