Question
Describe briefly, with the help of a circuit diagram, how a potentiometer is used to determine the internal resistance of a cell.
Solution
Potentiometer can be used to measure the internal resistance of the cell.
A cell of emf E is connected across the resistance box through key K1.
When key K1 is opened galvanometer shows deflection at the balancing length l1.
So, E = k
If both keys are closed, then balancing point is obtained at length l2 (l2 < l1).
So, V = k
Now, using the relation,
Therefore, we have