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A cell shows an open-circuit (terminal) potential difference of 6 V, which drops to 4 V when it delivers a current of 2 A. Determine the internal resistance of the cell.

1 ohm
2 ohm
3 ohm
4 ohm

Correct answer: 1 ohm

Solution

EMF = 6 V, terminal V = 4 V at I = 2 A, so r = (6 - 4)/2 = 1 ohm.

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