JEE MainPhysicsCurrent ElectricityMCQ+4 / −1
In the circuit, the galvanometer shows zero deflection. If the batteries and have negligible internal resistance, the value of the resistor will be - 

- A
- B
- C
- D
View written solutionFree
Correct answer: A
- Use the condition for zero deflection of galvanometer
If the galvanometer shows zero deflection, then the two junctions connected by the galvanometer are at the same potential.
That means the circuit is a balanced bridge.
So, for the two arms,
- Apply balance condition to the given circuit
From the figure, the ratio of resistances in one branch is equal to the ratio in the other branch. Using the values shown in the circuit, we get
Therefore,
- Check options
- A: ✅
- B: ❌
- C: ❌
- D: ❌
Hence, the required resistance is
- Comparison with stored answer
Stored correct answer: A
Our derived answer: A
So, the derived answer agrees with the stored answer.
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