# AC circuit: Find the V1 and V2

#### michgkou

Joined Oct 3, 2019
37
Hi, I tried to solve this using KCL. Ι would like a confirmation.

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Thanks

#### The Electrician

Joined Oct 9, 2007
2,751
You didn't finish your work, so I can't compare to my final result.

You have a lot of unnecessary algebra which invites mistakes as a result of including the 3+j2 branch between nodes 1 and 2. That branch is connected in parallel with a voltage source, and therefore has no effect on the voltages at node 1 and node 2.

It would probably be worth while to eliminate that branch and do it all over again.

#### michgkou

Joined Oct 3, 2019
37
You didn't finish your work, so I can't compare to my final result.

You have a lot of unnecessary algebra which invites mistakes as a result of including the 3+j2 branch between nodes 1 and 2. That branch is connected in parallel with a voltage source, and therefore has no effect on the voltages at node 1 and node 2.

It would probably be worth while to eliminate that branch and do it all over again.
This is my final result.

Why to eliminate that branch, the current thougth them is 0 because of the parallel voltage source (?)

Thanks.

#### michgkou

Joined Oct 3, 2019
37
Maybe it will be beter if I move the ground to the node 1. The V2 it will be 5 and I have to find one node.

P.s.: the exercise says to determine the currents of all branches ( not V1 and V2) but if found the V1 and V2 then we can found the currents.

#### The Electrician

Joined Oct 9, 2007
2,751
Your answers are very close to mine, which suggests to me that you have made a minor arithmetic error.

Here is the error I found; 33 should be 23. There may be more errors, but what do you get if you fix that one?

Are you using a calculator for the complex arithmetic?

#### michgkou

Joined Oct 3, 2019
37
V1=4.589∠-99.66°
V2=6.193∠-46.93°

yes, I'm using calculator

#### The Electrician

Joined Oct 9, 2007
2,751
OK You have the correct values now. I don't understand how your calculator could get 33 when the correct result is 23? Is it just a case of being careless when copying the result from your calculator to paper?

It seems that almost all of your mistakes in the various problems you've posted are simple arithmetic mistakes. You obviously understand the fundamentals of circuit analysis. As you said in one of the other threads, you will have to be more careful.