In a potentiometer arrangement, a cell of emf 1 . 20 V gives a balance point at 36 cm length of wire. This cell is now replaced by another cell of emf 1 . 80 V . The difference in balancing length of potentiometer wire in above conditions will be _____ cm .

Step-by-step solution

In a potentiometer, null point or balance point is defined as the point where the deflection of the galvanometer is zero. If emf of the unknown battery is ε then, ε = (Potential Gradient) × (Balancing length l ). Therefore, ε 1 ε 2 = l 1 l 2 ⇒ 1 . 20 1 . 80 = 36 l 2 ⇒ l 2 = 18 × 3 = 54   cm Hence, difference in balancing length is l 2 - l 1 = 54 - 36 = 18   cm