Mesh Current Analysis for a Series-Parallel Circuit

[gomezfx]

Homework Statement

Homework Equations

Not necessarily any equations ,just systematic approaches for mesh current analysis like using KVL
Also used cramer's rule

The Attempt at a Solution

My work:
http://i28.photobucket.com/albums/c216/aldodesigns/page1.jpg
http://s28.photobucket.com/albums/c216/aldodesigns/?action=view&current=page2.jpg

I found I1, I2, and I3 (I think) but they're not right. The answers my instructor gave us were 8A for the 110V source and 10A for the 12V source and I am way off. Did I set up my equations wrong?

 

[ehild]

Take care of your signs. Across a resistor, the current direction is always from the more positive terminal to the more negative one. If you decided the direction of current than you have the voltage drop always in that direction. You do not have the freedom to choose which terminal of a resistor is more positive than the other one, and you do not know it before you solve the problem for the currents.

So your first equations for mesh 1 and 3 are wrong.

In case of mesh 1 you have the current I1 - I2 flowing through the 12 ohm resistor. Going clockwise, the voltage drop is 12(I1-I2). In mesh 3, I3 current flows through the 4 ohm resistor, causing 4 (I3) voltage drop.

ehild