Q. A moving coil galvanometer has a resistance of 10$\Omega$ and full scale deflection of 0.01A. It can be converted into voltmeter of 10V full scale by connecting into resistance of
A) 9.90$\Omega$ is series
B) 10$\Omega$ in series
C) 990$\Omega$ in series
D) 0.10$\Omega$ in series
Explanation
(c) Let G be resistance of galvanometer and $i_{g}$ the current through it. Let V is maximum potential difference, then from Ohm’s law
$i_{g} = \frac{V}{G + R}$
$\Longrightarrow R = \frac{V}{i_{g}} - G$
Given $G = 10\Omega,\ \ i_{g}\ = 0.01A$
$V = 10\ volt$
$\therefore\ \ \ \ R = \frac{10}{0.01} - 10 = 990\Omega$
Thus, on connecting a resistance R of 990 $\Omega$ in series with the galvanometer, the galvanometer will become a voltmeter of range zero to 10V.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.