# Electrical circuit related problem

1. Sep 16, 2013

### Yammy

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

Determine the value of the voltage Vx
across the 3A current source.

2. Relevant equations

3. The attempt at a solution
I am really confused about how to do it. What I thought of is to find the voltage across the 4 ohm resistance which is 12 V. I though of subtracting that from the power sources.

But I am not sure which power source should be positive and which one should be negative?
Should I just assume the bigger 6V to be positive just because it is the bigger power source?
I might be completely wrong on this one. So please help me. This is not really a homework problem, this is in one of my practice tests, so I would appreciate any proper explanation I can get, rather than vague hints.
Thank you.

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2. Sep 16, 2013

### Yammy

Oh and please look at the attachment for the diagram

3. Sep 17, 2013

### Staff: Mentor

Sure, sounds like a good idea. Use KVL around the left loop.
The voltage sources are labeled with their polarities so no need to guess! Just do a "KVL walk" around the loop in either direction and sum up the potential changes as you go. The math will take care of itself.

4. Sep 17, 2013

### Yammy

ya u r right. Got it and thanks a lot.