I'm quite confused by mesh analysis. I understand that the idea is basically to apply KVL to each mesh. For example, if you have a loop that contains, say, a 3ohm and 2ohm resistor, and that's it, what is the correct KVL equation? Is it simply 0=3I+2I? As another example, check out this page: http://en.wikibooks.org/wiki/Electronics/Mesh_Analysis At the bottom, I can understand the first equation: you have a 9V source, and the resistors must cause a 9V voltage drop. But the second equation, I don't understand. Why is the first term positive?