# Solve for Unknown

• Nov 18th 2009, 08:56 AM
Len
Solve for Unknown by Setting up Equations
http://img7.imageshack.us/img7/2802/mathhelp2.jpg

The picture on the right is the original picture and the picture on the left is where I connected the battery. This is determined by the last digit in my student number which is 3. The A and B which are the wires from the battery are different from the A and B in the circuitboard(I think).

I need to solve for the current in the wire 2 to D. I have no idea how I would do this.

I was helped yesterday with this problem

http://www.mathhelpforum.com/math-he...offs-laws.html

and I would assume I would have to do something similar but there is no given circuits and current directions.

All the info I get is here in this pdf. (Part 2)

http://www.math.yorku.ca/Who/Faculty...ss2041-409.pdf

If anyone could give me a nudge I am sure I could solve this.

Thanks,

Len
• Nov 18th 2009, 01:26 PM
qmech
Getting started on the circuit
So this is essentially the same problem as before, just with more vertices and loops. You now have to label each edge of the circuit with i1, i2, i3, etc., and you can assign directions arbitrarily. However once you assign them, you have to stick with that direction through the whole problem. You can, of course, reverse the arrow in your equation by writing -i instead of i. After you assign all the edges with names, you can do the same thing as before and get vertex equations and loop equations.

In your circuit, if you want, you can collapse node 0 and 1 immediately by adding resistances.