# Nodal analysis problem

Discussion in 'Homework Help' started by cheypr, Nov 5, 2009.

1. ### cheypr Thread Starter Active Member

Oct 13, 2009
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OK here is the problem: use nodal analysis to find Vo in the circuit at R6. It is supposed to be 7.57v.

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• ###### element values.GIF
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Last edited: Nov 5, 2009
2. ### hgmjr Retired Moderator

Jan 28, 2005
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If you will post what you have done so far to solve the problem we can help you get past your snag point.

hgmjr

3. ### cheypr Thread Starter Active Member

Oct 13, 2009
34
0
OK and here is what did. This is the closest I've become. What I'm doing wrong?

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Oct 13, 2009
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5. ### cheypr Thread Starter Active Member

Oct 13, 2009
34
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this could help. its a solutio to the problem. the solution is so quick that i dont see how they found the answer.

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6. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,666
473
I don't see how they get an answer, either. They only have 4 equations, but there are 5 unknowns. The current Is2 doesn't appear in any of their equations, but surely it has an effect on the solution.

Perhaps they got an answer from a solution book.

7. ### cheypr Thread Starter Active Member

Oct 13, 2009
34
0
thanks, any other idea or suggestion in how to solve this exercise.

8. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,666
473
Your equation for SN2 is incorrect.

You have:

-(1/1k)Va + 0Vb + (1/1k+1/1k)Vc + (1/1k)Vd = -.002

You should have:

-(1/1k)Va + 0Vb + 0Vc + (1/1k+1/1k)Vd + (1/1k)Ve = -.002

Code ( (Unknown Language)):
1. [ .0025  -.0005 -.001 ]
2. [ -.0005  .001    0.  ]
3. [ -.001    0.    .003 ]
Solving will give you :

Va = .69565
Vb = 4.3478
Ve = 7.5652

9. ### cheypr Thread Starter Active Member

Oct 13, 2009
34
0
Thanks a lot. You all are a good help!!

10. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
Just for 'fun' I thought I'd try a different approach .... I know - I should 'get a life'.

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11. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,666
473
I don't know what you mean by "v1 = 4.2 A"; it looks like you're saying that v1 = 4.2 amps.

And when you say "voltage = 33.6", what voltage are you referring to?

Look at the designators in the .pdf file attached to post #3. Then:

Va = .69565
Vb = 4.3478
Vc = -5.3043
Vd = -4.43478
Ve = 7.5652