Question

A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected acrose the given cell, has values of.
(i) infinity (ii) 9.5 Q
The 'balancing lengths, on the potentiometer wire are found to be 3m and 2.85 m, respectively.
The value of internal resistance of the cell is:

Answer 1

Ans is (3)

             Internal resistance of cell

               \(r=\left(\frac{\ell_1-\ell_2}{\ell_2 }\right)\left(R\right)\)

                 \(=\left(\frac{3-2.85}{2.85 }\right)(9.5)\)

             = 0.5 Ω

Answer 2

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