On interchanging the resistances, the balance point of a meter bridge shifts to the left by 10 cm. The resistance of their series combination is 1kΩ. How much was the resistance on the left slot before interchanging the resistances?

Let the resistance in the left slot be R1 and position of balance point l1. Resistance in right box R2 = 1000 - R1. Its corresponding balance point l2 = 100 - l1. Using balanced wheat stone bridge equation, R1/R2 = l1/(100 - l1) (1) Given : l1 - l2 = 10 cm ∴ l1 - (100 - l1) = 10 ⇒ l1 = 55 cm From (1), R1/(1000 - R1) = 55/45 ⇒ R1 = 550 Ω