question_answer

In the potentiometer circuit shown, the balance point is at X. State with reason, where the balance point will be shifted when, Potentiometer circuit

(i) resistance R is increased, keeping all parameters unchanged.

(ii) resistance S is increased, keeping R constant.

(iii) cell P is replaced by another cell whose emf is lower than that of cell Q.

Answer:

(i) If resistance R is increased, the balance point shifts towards B, because when R is increased current flowing in the circuit will decrease and the potential drop per unit length also decrease, so balance length will increase.

(ii) If S is increased, there is no effect on the null point. As at balance condition, no current is drawn from cell Q.

(iii) If emf of P is lower than emf of Q, the potentiometer will show one sided deflection. The emf of cell in main circuit should be more than emf of primary cell.