Question

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

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

Answer 1

The correct option is A $2450\Omega$ in series

$R_g=50\Omega ,I_g=25\times 4\times {10}^{-4}={10}^{-2}A$

Range of $V=25volts$

$V=I_g(HR+R_g)$

$\therefore HR=\frac{V}{I_g}-R_g=2450\Omega$