Electrical Engineering: Ch 3: Circuit Analysis (5 of 37) Nodal Analysis w/ Current Sources: Ex. 3

In this video I will find the currents of a circuits with 2 current sources using nodal analysis.

Next video in this series can be seen at:

[swimcoach]

I took EE in 1966 and still think this is the coolest thing I ever saw. On this one I stopped the video after the assignment of the current directions and decided that with the two current generators converging at the same point, they should send the current through the low 2 ohm resistor which is oposite of the assumption. To my surprise I was correct which proves that if we guess wrong about the current directions it is no big deal and nobody will think we were stupid. It could have easily gone the other way. You could make up 1000 of these and I would still be amazed at how well the system works and has our backs.

[Mikebigmike]

Can't believe im back again, can always trust on your videos! Ive done a couple of computing and programming courses with the university but im always drawn back to science and engineering!

[salaarahmad]

Sir, you've done a wonderful work recording these helpful lectures for us.

[kurt_femboy]

thank you very very much for your awesome work, prof. Van biezen

[sasidharasarma]

I’m just wondering that if you had any exceptional abilities to teach every subject you know with

[walshaikhli]

Thank you. Your playlists are a great resource. :)

[TheNightDevilX]

Through row eschelon form of matrix, I got a result: v1=20, v2=24, i1=4, i2=-2, i3=6. This all adds up, but is it correct to have answers like this?

[TharunRPrakash]

Respected sir,
What if, if a resistor is attached directly to the current source? Then how'll be the equation?

[luklikme]

Respectfully Sir, I used the following approach and had it right too and it checked out with my current equations. But different answers altogether

SAME V1 AND V2 NODES. I assigned my currents, ( i1, i2 and i3) differently.

Had i1 current direction leaving V2 into the 4ohm Resistor . 

i2 current direction through the 5ohm resistor going into the V1 node.

My i3 through the 2ohm resistor entering Node V1.

Came up with the following : 
@ Node V2,
i1 + i3 = 6 + 2 => i1 + i3 = 8

@ Node V1,
i2 + i3 = 6

Using KCL : i1=V2/4. i2 = -V1/5. i3 = (V1 -V2)/2 I had the following solving for V1 & V2:

V1= 14.30v. and V2 = -3.430v


And ultimately, I had the following current values :

i1 = -0.86A. i2 = -2.86A. i3= 8.86A

Please could I be wrong in my approach, because I've verified it over and over. Please your help will be very much appreciated. Thanks

[BentHestad]

Hm, Sir; How can 6 Amps flow from node v1 with potential -1.8 V to node v2 with potential above 9 Volts? Or does this potential gap dont matter if the current is being pushed??
Thanks again for superb videos, my big fear is that all this one morning has disappeared! Catastrophy for many of us!

[theofiloseleftheriadis]

i Have the same results with a slight difference. The voltages have the opposite sign. I also noticed that you consistently assume in a certain yet for me not discernible way the precedence on which voltage you have to subtract from which. Please clarify.

[alanmathew]

Hi Sir, how are you determining the direction of the current in the branches, such as i1, i2, i3? Is there a certain method for that?

[shivamkapoor]

how do you know what node to connect to ground? can it be anywhere in the circuit????

[shazulsahrof]

Helo sir, why when im doing the subtitution method its always lead to different answers?, or in this case we cant use subtitution method?

[EEAMD-conw]

i try to do the algebraic "input" method like last example, but i do not get correct answers according to yours/ ltspice. ive checked my algebra, it looks allright

[MrBusinesssocks]

I got v2 3.5 and v1 -10.96 and they both work when substituted into the equations....

[zwehtetnainai]

Isn't i1 supposed to leave from V1 to ground 0 ?

[MoneyMastery]

i got v1= 20v, and v2 = 24v (i1= 4A, i2= -2A, i3= 6A) and when i checked my numbers i find them correct

[ande_samuel_stud]

Well i didn't understand how to assign current directions?