GATE 2024 IN – Question 54
Consider the figure shown. For zero deflection in the galvanometer, the required value of resistor Rx is ____ Ω (rounded off to nearest integer).
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Correct answer: 58 to 62
Explanation
The middle and bottom branches have the same left:right resistance ratio $40:60$. Their midpoints therefore have equal potentials, so no current flows through the vertical 60 Ω resistor. Zero galvanometer current requires the upper branch to have this ratio too: $R_x/90=40/60$.
Thus $R_x=\boxed{60}$ Ω.