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Question
Draw a labelled circuit diagram of a potentiometer to measure the internal resistance ‘r’ of a cell. Write the working formula (derivation is not required).
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Solution
The internal resistance can be found using the formula
`r = R(l_1/l_2- 1)`
where R is the resistance of the resistance box connected to the cell through key K2 and l1 and l2 are the balancing lengths corresponding to the cases when key K2 is open and is closed respectively .
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