Question

A galvanometer of resistance $50\Omega$ giving full scale deflection for a current of $10$ milliampere is to be changed into a voltmeter of range $100$V.
A resistance of ________$\Omega$ has to be connected in series with the galvanometer.

• A. $9950$
• B. $10025$
• C. $10000$
• D. $9975$

Answer 1

The correct option is A $9950$

Galvanometer resistance $R_G=50\Omega$
Current flowing $I_G=10\times {10}^{-3}A=0.01A$
Voltage range $V=100$ volts
Let the resistance to be connected in series be $R_s$.
Using $V=I_G(R_G+R_s)$
$\therefore$ $100=0.01(50+R_s)$
$⟹R_s=9950\Omega$