# Circuits, Kirchoffs

1. Nov 6, 2008

### Sheneron

1. The problem statement, all variables and given/known data

http://img185.imageshack.us/my.php?image=p2827altvk4.gif

(b) Calculate the potential difference between points a and b.

3. The attempt at a solution

I have solved the circuit using Kirchhoff's laws; I had to solve for the current in the 2 ohm resistor. But I am stuck at this question. I surmised that the potential difference would be using the 2 ohm resistor since we solved for it specifically. I found the potential difference at that resistor, and that yielded the correct answer but I have no clue why. I was wondering if someone could explain this to me? Thanks.

2. Nov 7, 2008

### Staff: Mentor

Not sure I understand your confusion. You solved for the voltages and currents in the circuit using KCL (most likely). That gives you the voltage across the 2 Ohm resistor and thus the current through it. Why don't you post your equations and solution, and point to what is confusing you about your final answer?

3. Nov 7, 2008

### Sheneron

Well my question is why do I use the 2 ohm resistor to find the potential difference at points a and b?