# applying nodal analysis on this simple circuit

Discussion in 'General Electronics Chat' started by PG1995, May 10, 2011.

1. ### PG1995 Thread Starter Active Member

Apr 15, 2011
753
5
Hi,

Almost all the details you will find in the given link below:
http://img171.imageshack.us/img171/9797/nodalysis1.jpg

You will find the expected (or, target answers) in the top right corner.

As you can see my value for V1 is wrong. It should have been 80V according to the answer given in the book. I have checked my equations several times but I found nothing wrong with them. Please help me with it. Many thanks for your help.

Cheers

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
This should probably be posted in homework.

Anyway --

As a simple check.

(1) ix+I3=10

(Don't think you used that relationship - from KCL at the ground node)

(2) I1=I3+4*ix

Combining (1) & (2) to eliminate ix gives

(3) I1+3*I3=40

We know that

(4) I1=(V1-V3)/2

(5) I3=V3/3

Substituting (4) & (5) into (3) gives

V1=80V

3. ### PG1995 Thread Starter Active Member

Apr 15, 2011
753
5
Thanks a lot, t_n_k. Many thanks.

You have it correct. But do you find my equations wrong? I know there could be different ways to tackle a problem. Yours is straight and simple but where did I go wrong? Could you please guide me? Even if my method was different, the end answer should have been the same. Please correct me. Once again, thanks.

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Yep ....

Equation at third line beginning "At V2: ..."

Ix=4Ix+I2 => 0=3Ix+I2 [rather than 0=5Ix+I2]

5. ### PG1995 Thread Starter Active Member

Apr 15, 2011
753
5
I'm such a fool! I added the term instead of subtracting it. I have been making such mistakes all the time. I have an exam a day after tomorrow. I think I'm going to fail it. Such 'trivial' mistakes alter the entire solution!

I'm very much grateful your help. My best wishes.

6. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
No worries - don't stress the small stuff. Most examiners are (hopefully) reasonably forgiving of such trivial errors - how they grade you will depend on how clear your method is otherwise.

7. ### PG1995 Thread Starter Active Member

Apr 15, 2011
753
5
Yes, you are correct. But my instructor only tallies the answers. If they don't agree, then it's all wrong. . Once again, thanks.

8. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
It's a cruel world sometimes.

9. ### PG1995 Thread Starter Active Member

Apr 15, 2011
753
5
So far, it has been "most of the times" a cruel place to live in for me, at least - I mean this world. But nice people like you and some other things are a kind of salvation for me!

With best wishes
PG