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 V, it should be connected with a resistance of:

• A. $2500\Omega$ as a shunt
• B. $2950\Omega$ as in shunt
• C. $2550\Omega$ in series
• D. $2450\Omega$ in series

Answer 1

Answer: (D)

$2450\Omega$ in series

Here, $I_g=25\times 4\times {10}^{-4}A={10}^{-2}A$
To convert the galvanometer into a voltmeter we must join a series resistance of
$R=\frac{V}{I_g}-G$
$=\frac{25}{{10}^{-2}}-50=2500-50$
$=2450\Omega$