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In a potentiometer experiment the balancing with a cell is at length 240 cm. On shunting the cell with a resistance of 2Ω, the balancing length becomes 120 cm. The internal resistance of the cell is

1. 0.5Ω
2. 1Ω
3. 2Ω
4. 4Ω

Correct answer: 2Ω

Solution

The internal resistance of the cell can be determined using the change in balancing length when the cell is shunted. The initial length of 240 cm corresponds to the full voltage of the cell, while the reduced length of 120 cm indicates that the voltage across the potentiometer has halved due to the shunt, which implies that the internal resistance of the cell is equal to the shunt resistance of 2Ω.

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