# Finding the Potential (Kirchoff's Law)

1. Feb 24, 2012

### Xarvist

1. The problem statement, all variables and given/known data
http://puu.sh/i8Bg

2. Relevant equations
V=IR
ƩV = 0

3. The attempt at a solution
Starting behind the left EMF source I sum the potential changes using Kirchoff's Voltage Law
150V - R2I - 50V - R1I = 0
Solving for I, I get 20Amps

However I know this can't be right because the potential at point Q is 97V
and after traversing the circuit, the potential according ot the calculated I is 110 Volts..

Can someone perhaps show me step-by-step to do problems like these?

2. Feb 24, 2012

### PeterO

Note that there is no Earth connected to this circuit, so no point on the circuit is necessarily at 0 V.

If the current flows anti-clockwise, the potential goes up 150 as you pass through the left battery, drop 40 or 60 through the bottom resistor [having trouble which resistor is which - one you start to reply the picture of the circuit is gone], drop another 50 going "backwards" through the ideal battery on the right, then another 60 or 40 through the top resistor.
So I think P should be at -13 or 7 depending which resistor was the 2Ω and which was the 3Ω

3. Feb 24, 2012

### Xarvist

Okay I understand everything but the very end. What calculations did you do to get those two numbers?

4. Feb 24, 2012