Q. The length of a wire of a potentiometer is and the emf of its standard cell is volt. It is employed to measured emf of a battery whose internal resistance is . If the balance point is obtained at cm from the positive end, the emf of the battery is -

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A

B

C

D

Solution:

Emf of a battery is given by, , where represents potential gradient of the potentiometer and balancing length of potentiometer.

l = balance length
L = length of potentiometer wire

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