JEE Main 2022 · 25 Jun · Shift 1 · Physics Q50

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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 ?

\dfrac13

deflection method cannot be used for determining the resistance of the galvanometer.

\dfrac13

deflection method can be used and in this case the G equals to twice the value of shunt resistance(s).

\dfrac13

deflection method can be used and in this case, the G equals to three times the value of shunt resistance(s).

\dfrac13

deflection method can be used and in this case the G value equals to the shunt resistance(s).

Answer and worked solution

Official answer: B

Method. With a large series resistance the total current stays about the same. A shunt $S$ that brings the deflection to $\frac13$ takes $\frac23$ of the current, so $\frac13IG=\frac23IS$ .

So $G=2S$ .

(B)

Topics:Galvanometer experiments Moving coil galvanometer

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JEE Main 2022 · 25 Jun · Shift 1, Physics question 50