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In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across 52 cm of the potentiometer wire. If the cell is shunted by a resistance of 5 Ω, a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell.

1. 1 Ω
2. 1.5 Ω
3. 2 Ω
4. 2.5 Ω

Correct answer: 1.5 Ω

Solution

The internal resistance of the cell can be determined using the ratio of the lengths of the potentiometer wire at balance points before and after adding the shunt resistance. The change in balance length indicates how the effective voltage across the cell changes due to the internal resistance, leading to the calculation that results in an internal resistance of 1.5 Ω.

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