Q 12-04-038JEE MainJEE Main 2026 (6 Apr, Shift 2)Medium
A moving coil of galvanometer when shunted with $2\ \Omega$ resistance gives a full scale deflection for a current of $500$ mA. When a resistance of $470\ \Omega$ is connected in series it gives a full scale deflection for $10$ V potential applied on it. The value of resistance of galvanometer coil is ______ $\Omega$.
Numerical value type. Enter your answer.
Answer: 50
Concept. Two conditions on the same galvanometer: as an ammeter $I_gG=(I-I_g)S$; as a voltmeter $I_g(G+R)=V$.
Step 1. Ammeter. $I_gG=(0.5-I_g)\times2\Rightarrow I_g=\dfrac{1}{G+2}$.
Step 2. Voltmeter. $\dfrac{G+470}{G+2}=10\Rightarrow9G=450$.
Answer. $G=50\ \Omega$.
Solution by Sreeraj P, M.Sc Physics
