(a) In a metre bridge [Fig. 3.27], the balance point is found to be at 39.5 cm from the end A, when the resistor Y is of 12.5 Ω. Determine the resistance of X. Why are the connections between resistors in a Wheatstone or meter bridge made of thick copper strips?

(b) Determine the balance point of the bridge above if X and Y are interchanged.

(c) What happens if the galvanometer and cell are interchanged at the balance point of the bridge? Would the galvanometer show any current?

A metre bridge with resistorsXandYis represented in the given figure. (a)Balance point from end A,l1= 39.5 cm Resistance of the resistorY= 12.5 Ω Condition for the balance is given as, Therefore, the resistance of resistorXis 8.2 Ω. The connection between resistors in a Wheatstone or metre bridge is made of thick copper strips to minimize the resistance, which is not taken into consideration in the bridge formula. (b)IfXandYare interchanged, thenl1and 100−l1get interchanged. The balance point of the bridge will be 100−l1from A. 100−l1= 100 − 39.5 = 60.5 cm Therefore, the balance point is 60.5 cm from A. (c)When the galvanometer and cell are interchanged at the balance point of the bridge, the galvanometer will show no deflection. Hence, no current would flow through the galvanometer. read less