Question

A galvanometer of $50\Omega$ resistance has $25$ divisions. A current of $4\times {10}^{-4}A$ gives a deflection of one division. To convert this galvanometer into a voltmeter having a range of $25$ volt, it should be connected with a resistance of :

• A. $245\Omega$ an shunt
• B. $2450\Omega$ in series
• C. $2500\Omega$ as shunt
• D. $2550\Omega$ in series

Answer 1

Answer: (B)

$2450\Omega$ in series

Given $R_g=50\Omega$,
$i_g=25\times 4\times {10}^{-4}A$
$={10}^{-2}A$
Range of $V=25$ volts
Resistance, $R=\frac{V}{i_g}-R_g$
$=\left(\frac{25}{{10}^{-2}}-50\right)\Omega$
$=2450\Omega$
Thus, a resistance of $2450\Omega$ is connected is series to convert it into a voltmeter.