Q 12-04-197JEE MainJEE Main 2020 (5 Sep, Shift 1)Medium
A galvanometer of resistance $G$ is converted into a voltmeter of range $0 - 1\ \text{V}$ by connecting a resistance $R_1$ in series with it. The additional resistance that should be connected in series with $R_1$ to increase the range of the voltmeter to $0 - 2\ \text{V}$ will be:
Answer: (D) $R_1 + G$
Full-scale current $I_g$: $I_g(G + R_1) = 1$ V. For $2$ V: $I_g(G + R_1 + R') = 2$ V.
Dividing: $G + R_1 + R' = 2(G + R_1) \Rightarrow R' = G + R_1$.
Solution by Sreeraj P, M.Sc Physics