Unbalanced Wheatstone Bridge voltage across resisitors

[msslowlearner]

Homework Statement

It is a qualitative problem. No values are given.
In an unbalanced Wheatstone Bridge, does the voltage across the resistors R4 and R2 change? In other words is Vr2of balanced bridge=Vr2 of unbalanced bridge? likewse for R4.

Homework Equations

The Bridge Balance eqn is R1/R2 = R3/R4, where R4 is the variable resistor. At balanced condition, Vr2 = Vr4

The Attempt at a Solution

The change in V_r4 is obvious. My problem was why does V_r2 remain constant??
I assumed that as current flows through R1 - Rg - R4 path, the current through R1 is also changing. But the current through R2 does not change as the extra Ig doesn't come into R2. I thought this was the reason behind V_r2 being constant.

But, the text said "the current through R1 doesn't change with change in R4. Hence, V_r2 does not change" ... How ?? I don't understand.. Is the text trying to say the current in the R1-R2 arm doesn't change at all ? Then what is the path of Ig from the source ??

 

[Studiot]

Look at post#11 here

https://www.physicsforums.com/showthread.php?t=450293&highlight=bridge+circuit

There are lots more descriptions of bridge circuits in the forums, have you tried a search?