# Nodal Analysis equations

Discussion in 'Homework Help' started by progolfer, Mar 11, 2011.

1. ### progolfer Thread Starter New Member

Mar 8, 2011
7
0
Hi all,

I am solving the circuit shown in the attachment by nodal analysis, I have already solved it using mesh and thevenins an am now trying to solve using Nodal analysis. I have come up with 3 nodal equations but when solving them iam getting a different answer to that of mesh and thevenins theorems. The 3 nodal equations I have determined are as follows could anyone tell me if I have made a mistake in them. the aim is to calculate the voltage across the 4 ohm resistor which is 2V.

Node A:

0 = (-Vb/2) + (17Va/10) - (Vc/2)

Node B:

11 = (Vb/2) - (Va/2)

Node C:

-5 = (-Va/5) + (9/20 Vc)

• ###### Nodal.doc
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Feb 16, 2010
112
5
For Node A: Look at the Vc term. Where does your -1/2 come from
For Node C: Consider the 4A source feeding into the node, it looks like you forgot it.

3. ### progolfer Thread Starter New Member

Mar 8, 2011
7
0
Sorry I meant to write -1/5 for node A, however I totally missed the fact that the 4A source was affecting node C, thanks for spotting this. The equation for node C should now read:

Node C: -1 = (-Va/5) + (9/20Vc)

Thanks