Question

What current passes through galvanometer in wheatstone bridge?

Answer 1

A galvanometer will have current flowing through it unless the bridge is balanced when voltage is applied to the bridge.

Here is a Wheatstone bridge circuit setup to measure an unknown resistance Rx. R1 and R2 are equal value precision resistors, say 100 ohms. R2 is a precision rheostat (variable resistor). When you adjust R2 to equal the resistance of Rx, then R1 and R2 act as a voltage divider equal to R3 and Rx. No current flows through the Galvanometer G because the voltage a points D and B are the same.

R2 has a calibrated dial, so when the galvanometer reads “null” or zero, then you know that the value of R2 is the same as the unknown resistor Rx.