question_answer

For the potentiometer circuit shown in the given figure, points X and Y represent the two terminals of an unknown emf e. A student observed that when the jockey is moved from the end A to the end B of the potentiometer wire, the direction of deflection in the galvanometer remains in the same direction. What may be two possible faults in the circuit that could result in this observations? If the galvanometer deflection at the end B is (i) more (ii) less, than that at the end A. Which amongst the two faults, listed above, would be there in the circuit? Give reasons in support of your answer in each case.

Answer:

The possible faults are as follows :

(i) The positive terminal of the cell E that of unknown emf is not connected at A.

(ii) The emf of the cell of unknown emf E is greater than the emf of driver cell.

If the deflection at the end B is

(a) more than A, then fault (i) would be there as driving cell unknown emf E equivalent to series combination of cells.

(b) Less than A, then fault (ii) would be there as two cells in series opposing each other and hence deflection at end B is less.