Question

A galvanometer has a resistance of 20w and reads full scale when 0.1 V is applied across it. To convert it into voltmeter of 10 V range, the U galvanometer should have a resistance of

• A. 1980 w in series
• B. 3980 w in series
• C. 980 w in series
• D. 1980 w in parelle

Answer 1

The correct option is B 3980 w in series

$R_g=20\Omega$

$V_g=0.1V$

$I_g=\frac{0.1}{20}$

$V=I\left(R_g+R_v\right)$

$20=\frac{1}{200}\left(20+R_v\right)$

$=4000-20=R_v$

$R_v=3980\Omega$

Hence,

option $\left(B\right)$ is correct answer.