Voltage drop between two points

[terryds]

Homework Statement

The question is: What's the voltage drop between point A and B ?? (Suppose that E2 > E1)2. The attempt at a solution

First, I need to solve the current flowing in this circuit, which can be done using KVL.
The current flowing is $\frac{E_2-E_1}{R_1+R_2+R_3+R_4}$ (which is clockwise in direction because E2 is bigger than E1)

But,I get confused in determining voltage drop between point A and B
I know that the formula is V = IR
But, I'm confused about the value of the resistor..

Is it R1 + R2 (since from point A to B the current flows from R1 to R2) ?
Or, should the resistor be the parallel series of R1-R2 and R3-R4 that makes an imaginary bridge between A and B ??

 

[gneill]

But,I get confused in determining voltage drop between point A and B
I know that the formula is V = IR
But, I'm confused about the value of the resistor..

Is it R1 + R2 (since from point A to B the current flows from R1 to R2) ?
Or, should the resistor be the parallel series of R1-R2 and R3-R4 that makes an imaginary bridge between A and B ??

Your first thought was correct. You determine the potential between two points by taking a "KVL walk" along a path that leads from one point to the other.

You could also have gone the other way around the loop (counterclockwise) from A to B, summing the potential changes along the way. In that case you would be "walking" against the current, so you'd see potential rises as you cross the resistors rather than drops.