# Homework Help: Nodal analysis question

1. Jun 13, 2010

### Cyb3rGlitch

1. The problem statement, all variables and given/known data

2. Relevant equations
KCL

3. The attempt at a solution

I recognise that the voltage sources form supernodes. This produces:

$$A - B = 10$$ -> $$A = 10 + B$$

We also know that node C is 12v.

I then form KCL equations:
$$6 + \frac{A - C}{12} = \frac{B}{40} + \frac {A}{24}$$

When I simplify this and sub in C and A, I get a ridiculous results. What am I missing here? Cheers!

Last edited: Jun 13, 2010
2. Jun 14, 2010

### Cyb3rGlitch

No one can help?

3. Jul 17, 2010

### Yaz Li

I think Vb-Va=10 -> Va=Vb-10.
To see this, write a kcl around the loop starting from the reference node to Node A and then Node B:

-Va-10+Vb=0 ->Va=Vb-10.

I have explained this on one of my posts:
http://circuits.solved-problems.com/resistive-circuits/nodal-analysis-supernode/ [Broken]
Scroll down to section three of the solution. Read the paragraph starting with "The voltage of Node III can be written in terms of the voltage of Node I."
It is also explained in my Nodal Analysis ebook, which can be downloaded from my website for free (a free and simple registrating is required though):
http://circuits.solved-problems.com/nodal-analysis/ [Broken]

Hope this will be of help.

Last edited by a moderator: May 4, 2017