# Circuit Analysis

1. Jan 18, 2009

### Xkaliber

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

(a) Suppose that R_1 = 6 ohms and R_2 = 3 ohms. Find the current i and the voltage v. See the diagram in the picture.

http://img291.imageshack.us/img291/7638/picturewr3.th.jpg [Broken]

2. Relevant equations

Kirchhoff's laws and Ohm's law

3. The attempt at a solution

I got v=12V and i=1A

However, I do not think that this is correct since a positive value for i means the voltage source is absorbing energy instead of supplying it, which does not make sense.

Last edited by a moderator: May 3, 2017
2. Jan 19, 2009

### LowlyPion

Why don't you write out your current loop equations and maybe we can see where you may be confused?

3. Jan 19, 2009

### Xkaliber

First, since the 3 amp current source is in series with R_2, the current through R_2 is 3A. Using Ohm's law, we find the voltage across R_2 to be 9 volts.

Now, KVL around outer loop: -12V - 9V + v = 0 -> v = 21V

KVL around right smaller loop: -9V + 21V - v_1 = 0 -> v_1 = 12V

Using ohm's law, current through R_1 = 2A

KCL @ top middle node: 3A - 2A - i = 0 -> i = 1A

If i does equal 1A, then according to the diagram in the picture, the voltage source is absorbing power since it is in the passive convention.

4. Jan 19, 2009