# Node Voltage problem

Discussion in 'Homework Help' started by prast, Apr 15, 2008.

1. ### prast Thread Starter New Member

Apr 15, 2008
5
0
Hello, I'm trying to write node voltage equations for Node A and B in the following circuit.

My issue is that all of the circuits I've done so far have had obvious "mutual conductance". This circuit however, I'm unsure of. Do they even have a mutual conductance through the unnamed node in the middle?

If there is no mutual conductance I'm thinking the equations will be something like this:

Node A: (0.75 mS)Va = 2mA
Node B: (0.5 mS)Vb = -2mA

So if this were the case Va = 2.67 V and Vb = -4 V

However I feel like there should be some type of mutual conductance here. Maybe something like:

Node A: (0.75 mS)Va - (0.5 mS)Vb = 2mA
Node B: -(0.5 mS)Va + (0.5 mS)Vb = -2mA

This would give Va = 0V and Vb = 4V

Any help would be greatly appreciated, thanks!

John

2. ### prast Thread Starter New Member

Apr 15, 2008
5
0
Perhaps I'm missing a source transformation or a supernode here?

3. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Neither of the sets of equations you have formed, account for the 10V dc source in the problem.

hgmjr

4. ### hgmjr Moderator

Jan 28, 2005
9,030
214
You did not mention in your initial post in this thread if a specific method to be used in finding the solution to the problem had been stipulated either by your instructor or in the problem statement.

Is the method to be used in solving the problem constrained in any way?

hgmjr

5. ### prast Thread Starter New Member

Apr 15, 2008
5
0
Sorry, the questions are:

a) Formulate node-voltage equations for the circuit.
b) Use these equations to find Vx and Ix

6. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Here is the link to the node voltage material in the AAC ebook. It would be good to review the material as a prelude to solving this problem.

hgmjr

7. ### guitarguy12387 Active Member

Apr 10, 2008
359
12
Ya, it's kind of hard to tell your methods here. If you give a little more of your work, it'll be easier to find out where (if at all) you're going wrong. I agree with hgmjr, you should read up a bit still. I'd just apply kcl a the unknown nodes. You'd come up with two equations, two unknowns... and voila!

8. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Prast,

You could rearrange the circuit as shown below if that helps you out.

hgmjr

9. ### prast Thread Starter New Member

Apr 15, 2008
5
0
Thank you hgmjr! The rearrangement was a big help!