Electrical Engineering: Ch 3: Circuit Analysis (8 of 37) Nodal Analysis w/ Voltage Sources: Ex. 1
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- เผยแพร่เมื่อ 31 ก.ค. 2024
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In this video I will find the currents of a circuits with 2 current and 1 voltage source using nodal analysis.
Next video in this series can be seen at:
• Electrical Engineering...
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I cannot even explain the love I feel for this man. God bless his soul for all the circuitry he has helped us with. Amen.
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Not a question at all but Sir I want to seriously thank you for all of the time and effort you put into your vids, Last semestre I stumbled upon your channel just to find that there was a treasure to be found. I'm currently studying an Electrical Engineering degree in Chiapas, México. I want you to know how greatful I really am for what you do here. Whenever I can, I always share your content with my classmates and even though a language barrier exists, that doesn't stop us from learning the same method in another fashion. Knowledge is universal, thank you for showing me that. Saludos desde Chiapas profesor. Much love.
Mucho Gracias
Michel van Biezen
@jcastañeda07
Can we talk?
@@MichelvanBiezen this is truly the only thing keeping me in electrical engineering as the covid-19 improvised online semester is sub par compared to your quality of teaching. Forever grateful!
Thank you! You are doing us all a great service by going above and beyond with these videos. Your explanations are clear and your process is taught way better than the books i read from and classes I am enrolled in. I feel like i struck gold with your channel. Thank you sooooooooooo much! You are amazing!
You, sir, single handedly summarized the past moth of my ECE 2k level course. Thank you.
I really appreciate your videos. The are so concise and to the point but also very explanatory. You're an Electrical engineer but have a very mechanical way of doing things. I really dig the bow tie
Thank you for sharing your awesome knowledge with us. I wish this was available when I tried attending engineering school in my mid-forties. I was not able to finish, and now I am 65 years old still with a desire to learn. Thank yoiu
So you are 70 now
@@Abdi_209 lol 71actually
probably dead
@@Abdi_209
Amazing how you used the Super Node!!!Thanks a lot for that super explanation!!!But there is only one mistake in current i1, it is: i1 = 5,6667 A (is wrong 0,2 A), i2 = -3,6667 A (it's ok) and i3 = -1,3333 A (it's ok too), so i1 + 12 = 2... 5,6667 + -3,6667 = 2 in node v1... in node v2 we get: i1 = i3 + 7, replacing the values: 5,6667 = -1,3333 + 7, that is 5,6667 + 1,3333 = 7 (ok). Finally we have in ground node, where V = 0: i2 + i3 + 7 A = 2 A, replacing the values: -3,6667 + -1,3333 + 7 = 2, that is -5 + 7 = 2 (ok). I hope it helps a little for clarifying this problem!!!
Sir like honestly God bless you, that's all I can say.
I have exam on June 4th, University is closed due to coronavirus and I was panicking. Thanks for your hard work putting these videos together as you are going to help me out. Reading books is okay, but sometimes you need someone to talk you through it, that is exactly what you are doing now. Much appreciated.
Hang in there and good luck on your exam.
Thanks you are awesome. Currently in Ghana doing basic electronics and I'm really grateful. Crisp and clear explanations Keep it up..
Welcome to the channel! Glad these are helping.
Thank you Sir for making all these videos. You are a great teacher.
I'm really enjoying your videos.
My gratitude to you is incalculable.
This example is also an example in the book im using for my online class. Your video was a great help since the book lacks the detail you provide. I am forever grateful.
Glad it was helpful!
at 6:40 he did so good kidding see 2 camera :D I love u sir :)
Honestly the best guidance I can get.
Sir? One question, why did you not include the i1 leaving node 1?
sir, what if there's a resistor in series with the voltage source?
والله يجدو انت عسل وشرحك جامدi appreciate what you do your student from Egypt
Glad you found our videos. Welcome to the channel! 🙂
What if the voltage source was replaced with the 2A current source in this circuit. how would u then find V1 and V2
You're the best I couldn't understand from my lecturer PDF. God bless you sir
Happy to help
In a later video, you used nodal analysis to solve a circuit with a voltage source without using a super node. It made me wonder why the super node was necessary here, so I came back and found that this circuit can also be solved without a super node. (It did however involve assigning a current between v1 and v2, but that turned out to be easy enough.) I also want to say thanks for these videos. They're extremely helpful!
It is not necessary, but using a super node does make it a bit easier. This is just an illustration of this method, which doesn't mean it cannot be solved in other ways.
But could there be a situation that v2=v1-2? It depends on how voltage source is connected, isn't it? I mean it could be connected with + directed to v1and - to v2 or other way around
sir do you have any book to suggest for practice???
Why isn't the i1 included in around 3:16?
When solving for the voltages (v2=v1+2), how do you determine the sign of the 2? Does v2=v1-2 give the same answer? Is it because of the polarity of the voltage source?
excuse me, I want to ask, is each symbol marked with + - a voltage source and that marked → is a current source?
you should be the one receiving my professor's salary. you are a lifesaver
Happy to help!
Just curious, why wasn't Isub1 included in your equation 4 at 3:05? And do you have AC circuits analysis (complex, phasors) thank you.
This is where we took the entire top loop and called it a "super node" to reduce the number of currents we need to consider all at once. Take a look at the playlist: PHYSICS 49 RCL CIRCUITS for AC circuits and phasors.
thank you sir you have really been pf great help
great service............ thank you sir
Wow thank you. I can't believe the division you do in your head, without a calculator!!!
Happy to help!
Hello Professor Biezen, I hope you're doing well
At approximately 5:58 you wrote that V_2 = V_1 +2, do you mind explaining the logic behind why this equation is valid? Is it because there is a voltage rise because of the 2Volt voltage source that is between the V_1 and V_2 voltage nodes?
Thank you :)
Between the two nodes that are notated as v1 and v2, there is a 2 V voltage source with the positive side to the right. That causes v2 to be 2 volts higher than v1
Thank you sir, I really appreciate it.
Sir , how did we get v2 to equal (v1 + 2) if we assumed that current i1 is flowing from node 1 to node 2? Thanks!
It’s also my question
Remember that v2-v1=2, we get the number 2 from the voltage source that already depicted in the circuit. Therefore we can get v2=2+v1 by adding both equation with 2.
@@damarabhinawa643 but if i1 was v1 - v2, why would the voltage drop be any different for the Supernode
wait nvm, i1 is going opposite of you know.. yeah nvm im slow lol
HOW IS IT POSSIBLE THAT i2 and i3 are negative and still can run this circuit? wouldnt there be a problem on the 10ohm resistor becauze both currents face each other in opposit flow? and if you want to calculate the voltage over the 10ohm resistor, do you have to take i2 or i1? cauze i2 is the real current through 10ohm. ANYONE?
The sign simply indicates the direction of the current. It doesn't matter which direction the current flows. In either case it will produce the desired effect.
So I took a slightly different approach with this one, I assumed 2V for the top right node, 0V for the top left node, and then left the bottom one as a variable. I assumed an unknown current coming out of the battery, and then for the currents in the branches I did the normal I=(v1-v2)/R thing. I got the same current answers as you. I'm curious why in your approach you didn't also start with 2 known node voltages instead of one. Does it matter either way?
Try it and see if you get the correct answer. (best way to learn).
How do we know where to put the nodes for v1 and v2???? can it be anywhere?
Knowing where to put them comes with practice. Essentially you can place them anywhere, but they tend to be chosen more towards the "major intersections" of the circuit. Is some cases you take a section of the circuit and make it a "super" node. Again, practice and doing lots of problems is the key to understanding that concept.
Nice explanations sir.
Thank you very much sir
GOD BLESS YOU SIR
Thank you. Glad you found our videos. 🙂
thx alot ur the best
we assumed vsub1 to be at higher voltage than vsub2 that is why we did vsub1 - vsub2 to obtain isub1
then why are the values after calculations not matching our assumptions
Since there is a 2 V voltage source between v1 and v2, we know that v2 is 2 V higher than v1.
hello michel....what happened @6.39 ? i am curious :D
+Yathin Raj Looks like my editor (my wife) decided to keep that in. (I was looking something up) :)
Thinking about this i believe it would make sense to assign one of the nodes connected to the voltage source as the reference node (with 0V). This immediately would give us the voltage of the other node connected to the voltage source (in this case 2V). It is basically the same logic, but the numbers & calculations would be a little bit easier.
I have a question. Why is there not an i4 that flows from V1 to V2 through the 2V voltage source? Thank you.
There is, but we don't need to worry about it since we encased it in the "super node".
@@MichelvanBiezen thank you! you are doing gods work
sir can we consider the loop below which contains 4 ohm and 2ohm resistors as a super node and do the analysis???
There are often multiple ways to solve a circuit. We learn many of these methods, and then we we start applying these skills we tend to choose the method we like the most individually. Try it and see if you get the same answer.
thank you sir
Why would you do mesh analysis given more voltage sources? Wouldn’t it be easier to do mesh analysis with more current sources?
These are just examples. Not a recommendation to use one method over another. After one has learned all the various methods, one will gravitate to their favorite method.
Dear sir, I have a question for you. Step number 4, when you using KCL why did not you include i(1) in your equation?
Because we replace the top mesh with a "super node" and only consider the currents leaving the super node.
@@MichelvanBiezen thank you , sir.
At 1:41 why do we not add a current at the voltage branch? Thank you so much for all your replies sir!
If you watch the rest of the video, you will see that we use a "super node" approach which simplifies the problem.
Won"t (v1- v2) equal 2V?
V2 is 2 volts higher than V1
Good stuff
I love your videos, they've been super helpful! But I have a question... Since i1 is also going in for the supernode, why isn't the equation 2+i1=i2+i3+7?
i1 is internal to the supernode. (that is why we use that method to eliminate one of the unknowns. )
Awesome. Thanks you! That makes sense!
Can you use nodal analysis by inspection method using this example? If yes can you make a video of it. Thanks and more power.
Essentially you can use any technique on any circuit. We have examples of most of the techniques used. The choice of the technique is one of personal preference. Some circuits can be more easily solved with some techniques.
Sir, I would like to ask you someth. (Why you don't take or assume actually a current pass through a voltage"2V" then we will ) see that the result will be the same of the that which will you had been write there . Thanks for you our teacher
In a circuit we are usually not interested in finding the current through a voltage source. In this case we didn't have to find it to solve the circuit. However there is nothing wrong with using a different method where you find the current through the voltage source.
Can we transform the sources to solve this using KVL? For example, can the current sources be transformed to voltage sources?
I would also like to add the fact that there's no words I can use to express my gratitude towards you professor, these videos are the only reason I'm surviving my course. Thank you so much!
There are many different techniques to solve circuits. For some circuits you can use almost all of them if not all of them. For some circuits certain techniques are better than others. The best way to learn that is to try two or more techniques on a single circuit and compare the results.
@@MichelvanBiezen I see, I tried solving by transforming the current source to voltage source and using KVL but I could not. I don't know if I was doing something wrong or if the process isn't right for this circuit. Either way, thank you so much!
Is there an alternate method to the supernode to solve these kind of problems?
There are many different methods to solve circuits. Eventually it becomes a personal choice. (But now we have to learn the methods the professor wants us to know).
Sorry i phrased the question wrong, i wanted to ask if there was an alternate method, while still using the nodal analysis, to solve a problem with a floating voltage source or is the supernode the only way?
sir you are wonderful.... thank you very much
Glad the videos are helpful.
Sir, i would like to know why v2=2+v1. Thanks!
+Kelvin Kwok The voltage at node 2 is 2 volts higher than at node 1 because there is a 2 Volt voltage source between the two nodes.
+Michel van Biezen sir, how do you know which one of the voltage is higher ? thanks
You decide arbitrarily and then the sign tells you if you were correct or not.
V2 must be higher than V1. Think it that way, you have V1 and that source ADDS 2 more voltage to that and it becomes V1+2, which we called V2
Note that, this happens because the voltage is getting increased from - through the +. If it was connected oppositely, V2 would be V1 - 2. Hope this helped
Respected Sir,
the place were you made a super node and you are keep saying that it a single node , then the resistors 2 ohm and 4 ohm share a single node ...
and if we separate them then it becomes a short circuit between the two...
then how come we can calculate two voltages V1 and V2 from a single node????
correct me if i am wrong...
We used the super node to eliminate one of the currents and therefore made the current equation simpler. But the two nodes still exist and v1 and v2 have a potential difference of 2V.
@@MichelvanBiezen okay....
Well thanks ...
Are you using a book or just personal notes?
We use a combination of our own notes and many reference sources.
Wouldn't v2 = v1-2? because voltage goes through a voltage rise and not a voltage drop. Voltage drop is usually a positive sign
The word "drop" means "decrease". Like a drop in height is a decrease in height. That said, some texts and some professors will hold themselves to a different convention.
Could you please give some examples with wattmeter in the circuit and how to solve that?
We are not sure what a "whatmeter" is. We have volt meters and current meters. We have videos on those in the physics playlists.
@@MichelvanBiezenwattmeter . Wattmeter. I wish I could post a picture of a wattmeter in a circuit here
Great explanation
Thank you.
isnt i1 leaving the super node?
i1 is inside the super node. (that is the purpose of the super node: to eliminate some unknowns.
I have a very important question.
the only way to make this work out . is to write V2-V1=2V
There's a problem, thus far you taught us to write in the direction of current, from higher to lower potential and thus based on that is should be v1-v2=2v which will gives us an entirely different solution.
NO ONE AT EGN Department can answer...…
im very confused why we do things differently from previous lessons
Note that the difference in potential across a voltage source does NOT depend on the current direction. Therefore you MUST use the potential difference across the source as indicated: V2 - V1 = 2V
Great video sir
Thank you. Glad you liked it.
Isn't there a current i4 through the 2 volt battery??
Yes, there is, but it is easier to make the top mesh into a "super node", which then eliminates one of your currents.
Sir why didn't we take i1 in the equation
good question! I happen to saw it in this video th-cam.com/video/xiRp2HQTenc/w-d-xo.html , pause at 2:43 and notice how I3 cancels.
6:35-6:40 When you feeling confident you did good job on exam but see your friend doing completley differently. The longer you loop it the funnier it gets :D
Why is i1 not included in the supernode equation?
That is the purpose of using a "super node", to eliminate one of the currents, which makes it easier to solve the problem.
@@MichelvanBiezen I understand, is that because in the equation (current in) = (current out) , i1 cancels?
The current doesn't cancel, but we don't need to know the details of what happens in the "super node". We only care about the current flowing into the node and the current flowing out of the node.
thanks a lot)
sir may you the concept of the super node?
We have a video like that in our electrical engineering videos.
why is v2-v1 = 2 & not v1-v2 =2 in the supernode
V2 is at a higher potential than V1
How did you know that V2 is V1 + 2?
Because there is a 2 volt voltage source between the two nodes. Therefore the potential v2 must be 2 volts higher than the potential v1
still very good . keep it up . just to let you know , i am depending your video .hahaha
❤❤
Fundementals of Electric Circuits
That is correct. These playlists cover the first 2 semesters of electic circuits.
I think there is a mistake... why didn't he assign current to the branch that has the voltage source...?
You can check yourself. In node V2, you are supposed to have I1 = 7+ I3. But that doesn't add up. Because you miss one more current, which is supposed to be 5.867A.
You are supposed to get this:
I1+ 5.867 = I3 + 7.
There is no mistake in this video. There is no voltage drop due to the current in that branch since it only contains a voltage source. The only relevant information is that the voltage increase by 2 volts between the 2 nodes.
@@MichelvanBiezen thank you very much for your reply. But how will you explain then that the amount of current in nod V2 doesn't add up?
Ok...ok... Technically you didn't make any mistake. You simply ignored the middle current, and it didn't affect your calculations...
But I think it's still a little bit confusing that you ignored that current, and you should have made it more clear. Thank you.
allah bless you
i love the fact that he wears bow tie, it's is cute. reminds me of young sheldon. thank you sir !
(06:37) Is it panic of 'am i recording?' 😂
I think you are right on that. (I was thinking: "are you recording this"?) And she did not edit it out. 🙂
@@MichelvanBiezen By the way, thanks for your lectures professor. It's my 4th year in electrical & electronics engineering, I've been watching your lectures since my first year. 🙂
Glad you found our videos and that you found them helpful. You are almost ready to graduate. Keep up the hard work! 🙂
3:39 looked hella funny!
Yes, I get stuck as well sometimes.
SUPERNODES !
thank you sir you have really been pf great help
thank you sir you have really been pf great help