A galvanometer of resistance $20 \Omega$ gives a deflection of 5 divisions when $1 \mathrm{~mA}$ current…

A galvanometer of resistance $20 \Omega$ gives a deflection of 5 divisions when $1 \mathrm{~mA}$ current flows through it. The galvanometer scale has 50 divisions. To convert the galvanometer into a voltmeter of range 25 volt, we should connect a resistance of
  1. $1240 \Omega$ in series.
  2. $2480 \Omega$ in series.
  3. $2480 \Omega$ in parallel.
  4. $20 \Omega$ in parallel.

Solution

$\begin{aligned} \mathrm{R} & =\frac{\mathrm{V}}{\mathrm{I}_{\mathrm{g}}}-\mathrm{G} \\ & \text { Here, } \mathrm{I}_{\mathrm{g}}=\frac{50}{5}=10 \mathrm{~mA} \\ \therefore \quad \mathrm{R} & =\frac{25}{10 \times 10^{-3}}-20 \\ & =2480 \Omega \text { in series }\end{aligned}$ ~

Asked in: MHT CET 2023 (09 May Shift 2)

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