Q 12-04-226JEE MainJEE Main 2019 (12 Apr, Shift 2)Medium
A moving coil galvanometer, having a resistance $G$, produces full scale deflection when a current $I_g$ flows through it. This galvanometer can be converted into (i) an ammeter of range $0$ to $I_0$ $(I_0 > I_g)$ by connecting a shunt resistance $R_A$ to it and (ii) into a voltmeter of range $0$ to $V$ $(V = GI_0)$ by connecting a series resistance $R_V$ to it. Then,
Answer: (D) $R_AR_V = G^2$ and $\dfrac{R_A}{R_V} = \left(\dfrac{I_g}{I_0 - I_g}\right)^2$
Ammeter: $R_A = \dfrac{GI_g}{I_0 - I_g}$. Voltmeter: $R_V = \dfrac{V}{I_g} - G = \dfrac{G(I_0 - I_g)}{I_g}$.
$$R_AR_V = G^2,\qquad \frac{R_A}{R_V} = \left(\frac{I_g}{I_0 - I_g}\right)^2$$
Solution by Sreeraj P, M.Sc Physics