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In a potentiometer setup, a cell of emf 1.25 V produces a null point at 35.0 cm of the wire. When this cell is swapped for a different cell, the balance point moves to 63.0 cm. Find the emf of the second cell.

1. 1.75 V
2. 2.00 V
3. 2.25 V
4. 2.50 V

Correct answer: 2.25 V

Solution

Since the balancing length is proportional to emf, the second cell's emf scales with the longer balance length.

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