Homework Help: I need help with kirchhoff rules

1. Apr 18, 2010

kliker

[PLAIN]http://img17.imageshack.us/img17/201/73448266.jpg [Broken]

let's suppose that we know all resistors and voltages

by applying kirchhof rules we have

V1 - i*R1 - i*R2 -i2*R3 = 0
V1 - i*R1 - i*R2 - i1*R4 - V2 = 0
-V2 + i2*R3 - i1*R4 = 0

we know V1,V2,V3 R1,R2,R3 and we can find the currents

now we have this image

[PLAIN]http://img220.imageshack.us/img220/4225/53762410.jpg [Broken]

it's the same circuit and we suppose that there are two currents ia and ib

now here we have this, is this right?

V1 = ia*R1 + ia*R2 - ib*R2
-V2 = ib*R4 + ib*R3 - ia*R3

is this correct? but if we find ia and ib, we know just two currents, I mean in the previous image we have 3 currents, i i1 and i2

here in the second image if these equations are correct we get the current ia which is the current i and ib which is the current i1

but we dont have only these 2 currents we have a third current too called i2, how can I find it here?