GATE 2023 IN – Question 30
When the bridge given below is balanced, the current through the resistor Ra is _____mA (rounded off to two decimal places).
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Correct answer: 0.99 to 1.01
Explanation
At balance, galvanometer current is zero. The equal 10 mΩ lower-triangle resistors form a 20 mΩ path through $R_a+R_b$, parallel to $R_c=10$ mΩ. The 3 mA entering divides inversely with resistance, so $I_{R_a}=3(10)/(20+10)=\boxed{1.00}$ mA.