# simple problem about nodal analysis

Discussion in 'Homework Help' started by PG1995, May 11, 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://img710.imageshack.us/img710/1565/exampleproblemnodalysis.jpg

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

As you can see my value for V1 is utterly wrong. It should have been 37.818V 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. ### Jony130 AAC Fanatic!

Feb 17, 2009
3,995
1,117
Your have a error in equation for node V2
I3 = I2 + 2A = V1/4 - V2/4 + 2 = V2/10 this is correct, but after that your simplification is incorrect.
I get this for node 2
5V1 - 7V2 = - 40

3. ### PG1995 Thread Starter Active Member

Apr 15, 2011
753
5
Thanks a lot, Jony.

I multiplied the above equation by "40". I don't see any error. What am I missing? 10V1 - 10V2 + 80 = 4V2 => 10V1 - 14V2 = -80.

4. ### Jony130 AAC Fanatic!

Feb 17, 2009
3,995
1,117
Oops I didn't note this.
I use this site to solve this for me
http://www.wolframalpha.com/input/?i=solve+for+V1++,+3V1+-+2V2+=+48+,+10V1+-+14V2+=+-+80+

And I get
V1 = 416/11 = 37.8181818V

V2 = 360/11 = 32.7272727V

For this equation
3V1 - 2V2 = 48
10V1 - 14V2 = - 80

5. ### PG1995 Thread Starter Active Member

Apr 15, 2011
753
5
Once again, many thanks Jony.

I made a very silly mistake at the end. While applying Cramer's rule I had incorrectly used "-4" instead of "-14". This was the reason for all the error. I just noticed it now . You are really nice.

Best regards
PG