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
Let $G$ be the coil resistance and $I_g$ its full-scale current.
With the shunt: $I_gG = (0.5 - I_g) \times 2 \Rightarrow I_g(G + 2) = 1$.
With the series resistor: $I_g(G + 470) = 10$.
Dividing: $\dfrac{G + 470}{G + 2} = 10 \Rightarrow 9G = 450 \Rightarrow G = 50\ \Omega$.
Solution by Sreeraj P, M.Sc Physics