Where potentiometer is connected across A and B, balancing length →64cm Then A and C then balancing tength → B cm. Let the be emf ε1 when connected across A and B and let emf be ε2 when connected acress B and C. we know that emf of potentiometer ∝ balancing length. ⇒ε1∝64 ε1−ε2∝8 Let the balancing length be lcm when the potentiometer is connected between B and C. ⇒ε2∝l using the above three equations we get, 64−l=8 l=64−8 l=56cm Hence the balancing length is 56cm.