In the circuit in figure, if no current flows through the galvanometer when the key is closed, the bridge is balanced. The balancing condition for bridge is.
C1C2=R2R1
In the steady state , no current is passing through the capacitor. Let the charge on each capacitor be q. Since the current through galvanometer is zero.
I1=I2
The potential difference between the ends of the galvanometer will be zero. Therefore,
VA−VB=VA−VD
I1R1=qC1..............(1)
Similarly , VB−VC=VD−VC
I2R2=qC2.............(2)
Divide (1) by (2) we get
C1C2 = R2R1