Q 12-04-142JEE MainJEE Main 2022 (25 Jun, Shift 1)Medium
A teacher in his physics laboratory allotted an experiment to determine the resistance $G$ of a galvanometer. Students took the observations for $\dfrac13$ deflection in the galvanometer. Which of the below is true for measuring value of $G$?
Answer: (B) $\dfrac13$ deflection method can be used and in this case the $G$ equals twice the value of shunt resistance $(S)$.
With the main current kept the same, a shunt $S$ is adjusted until the deflection falls to one third, so $I_g = \dfrac I3$ and $I_S = \dfrac{2I}{3}$.
$G$ and $S$ are in parallel: $G\cdot\dfrac I3 = S\cdot\dfrac{2I}{3}\Rightarrow G = 2S$.
Solution by Sreeraj P, M.Sc Physics