JEE Main 2026 Apr 6 Shift 2, Physics Q23: Wheatstone Bridge, Ammeter, Voltmeter And Potentiometer

JEE Main2026Apr 6, Shift 2Physics

A moving coil of a galvanometer when shunted with $2 Ω$ resistance gives a full scale deflection for a current of 500 mA. When a resistance of $470 Ω$ 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 _____ $Ω$ .

Your answer

Solution

Shunt condition. Total current $I = 0.5$ A splits between coil ( $i_{g}$ ) and shunt ( $I - i_{g}$ ). Voltage equality across the parallel pair:

$i_{g} R_{g} = (0.5 - i_{g}) \cdot 2$ $\Rightarrow$ $i_{g} = \frac{1}{R _{g} + 2}$ .

Series condition. With 470 $Ω$ in series and 10 V applied, the same full-scale $i_{g}$ flows:

$10 = (R_{g} + 470) i_{g} = \frac{R _{g} + 470}{R _{g} + 2}$ .

$10 (R_{g} + 2) = R_{g} + 470$ $\Rightarrow$ $9 R_{g} = 450$ $\Rightarrow$ $R_{g} = 50 Ω$ .

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JEE Main 2026 Apr 6 Shift 2, Physics Q23: Wheatstone Bridge, Ammeter, Voltmeter And Potentiometer

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