Thevenin's Theorem Explained (With examples of Independent and Dependent Sources)
ฝัง
- เผยแพร่เมื่อ 7 เม.ย. 2017
- In this video, we will learn about the Thevenin's Theorem in the electrical circuits.
Thevenin's Theorem is a very useful technique in solving the circuit problems when your entire focus is on a particular element in the network and you are not bothered much about the remaining network or circuit.
So, using this Thevenin's Theorem we can replace the entire circuit by the Thevenin's equivalent voltage source in series with Thevenin's equivalent resistance across it's terminal.
So, in this video, we will see that how to find this Thevenin's equivalent voltage and Thevenin's equivalent resistance.
Now, there are three different possible cases of the circuit for which we can find the Thevenin's equivalent circuit.
1) Circuit contains only independent sources.
2) Circuit contains independent and dependent sources.
3) Circuit contains only dependent sources.
So, in this video, we will see that, how to find Thevenin's equivalent circuit for all these cases with an example for each case.
At the end of the video, we will see Norton's Theorem which is dual of Thevenin's theorem and will see that how to convert any Thevenin's equivalent circuit into Norton's equivalent circuit using the source transformation.
The time-stamped link for the different topics is given below:
0:20 Usefulness of Thevenin's Theorem
4:04 Thevenin's theorem for the circuit which contains only independent sources.
6:58 Thevenin's theorem for the circuits which contains independent and dependent sources.
11:49 Thevenin's theorem for the circuits which contains only dependent sources.
14:42 Norton's theorem
Link for the other useful videos:
Classification of Electrical Network:
• Classification of Elec...
Source Transformation:
• Source transformation ...
This video will be helpful to all the students of science and engineering in understanding the Thevenin's Theorem in the electrical circuits.
#TheveninTheorem
#TheveninExamples
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Minor correction:
5:30 In Case 1, the value of Vth will be 15 V instead of 5V.
it is -15V
10-10(-0.5)
-10(-0.5)=+5 so,
10+5=5
So helpful thank you!!
can u please mention this in the description instead. also good idea wioth the time stamps
I have already Pinned this comment.
I just came here to see what to do with the dependent sources. But I got to learn why this theorem is needed. Thanks for that.
anybody who is confused about voltage Vab in case 1 see below:
just apply KVL at node A like this:
0=(Va-10)/10 + (Va-20)/10
SO 2Va = 30
Va = 15v
Note: B is taken as ground so Vab is now only Va as Vab= Va-Vb
You've applied kcl not kvl
@@madhur7590 he did node voltage to prove there's a mistake. i literally looked to the comments because i was certain that first mistake was an error
Wow thanks....I needed this😁
Thanku brother' my mind was blowing regarding this before seeing your comment ❤️🙌
Yes. Vab in first case is 15 volt
review:
Only independent sources: remove selected resistance, calculated voltage via mesh analysis and resistance via removing sources
Independent and dependent: Apply KCL on dependent sources and short A and B to find volt and resistance
only dependent: apply 1v/1A source from B to A to find the resistance, as it is equal to Va (Volt = 0)
In case 1..there is a mistake...Vth is 15V not 5V
Yes, you are correct Nikhil. Thanks for mentioning it.
do u start reading comments before commenting
@@gaddamful no you moron he commented after readding
you're the boss. you explain the theory well and also the practical applications. Thank you
One doubt...why to make independent sources zero while calculating thevenin's resistance?
What is the significance of this point??
Also what does thevenin's voltage actually mean
Very helpful, thank you!
Why in the second case, didn't short ckt the voltage source
Awesome video sir! Thank you! Exactly what I need!
Sir suppose if we take 20v in order to find out vth then value of vth will be change
ckt contain dependent src, i got value of vth is 15v if am applying kcl..is dis value rgt?
This video helps me a lot. Clear explanation + good examples. Thanks @All About Electronics.
Best explanation i have ever seen on TH-cam ... Thanku sir for helping students like us
This video clear my all concepts of dependent and independent sources
Could you please tell me the applications of Thevenin's , Norton's, Reciprocity, superposition and maximum ower transfer theorem.
In case 2 if the independent voltage source was present in the place dependent voltage source and vice versa than after short circuiting does the independent voltage source gets short circuit or not
in case 2 ,if dependent source value replace by 20i then how will write node eqn
Sir if a circuit contain only independent then can we apply 2nd method i.e the method of short circuit and finding Isc
Thank you.. I understood it well😊
I’m so confused about the 2nd case when he shorted the resistance and the dependent source. How?
yeah ,me too.Why is it that the dependent source is alsoshort circuited as the terminal A and B is short circiuted
He doesn't explain it well. The reason is that when he applies the short circuit across the terminals A and B, the voltage across those terminals is zero, thus the voltage of the dependant source (3.VAB) is now also equal to zero, so can be replaced with a short circuit.
@@anglotenglish6001 oo yes yes. Thanks for your explanation
@@anglotenglish6001 no he was mistaken when he short circuited the dependent voltage source.
what you said is only true if the dependent voltage source was connected in PARALLEL to a and b terminals then that would be a short circuit.
the dependent source actually becomes connected in parallel to the 2k ohm resistor
@@anglotenglish6001 thanks man .you saved me from confusion.
in # case 2 why don't we remove 1kohm resistance across AB..(we removed it in case 1)
I"m still trying to intuitively understand why we short circuit a voltage source but open a current source when calculating Thevenin's resistance. Why the difference in how these two are manipulated? I guess voltage makes sense. After all, there is no resistance in an ideal battery. The best I can come up with as far as a current source is the way it is usually in parallel to a resistance, and so opening the source, which will never change depending on the load characteristics, is fair. Anybody have other ideas?
5:22 The minus in the last equation should be replaced by plus
Thank you for the video, it's really of value
Your explanations are so cool 💯
Great thanks for you
Dr sherif ahmed from egypt
TOO GOOD. THANK YOU!
how did you consider Vab at 5:17
In case 3, is the 3i dependent source a current-controlled voltage source, if not then how did you subtract 3i from Va in case it is not a voltage source (that would be like subtracting current from voltage otherwise).
Yes, I think it is a CcVs , and the symbol of a dependent voltage source is also there.
If it was a current source, an arrow(symbol of a dependent current source) would have been used.
Very blnice video and easily understood that.
Sir I didnt understand how did u get Vab=10-(10i)
To find, Vab, KVL has been applied in the loop. Now, Vab = Va- Vb ( the Potential difference between Node A and B).
As node B is reference node, so the voltage at that node will be zero.
Now, the voltage at Node A will be 10 - (10I) (that is 10V - voltage drop across 10-ohm resistor, using KVL)
And hence, Vab = 10 -(10I)
I hope it will clear your doubt. If you still have any doubt then do let me know here.
sir how is node b a reference node
See, node B is at zero potential. Or in another way, if say, it is a ground of the circuit. And in the circuit generally, the node with zero potential is considered as the reference node. I hope, it will clear your doubt. If you still have any question then do let me know here.
what if both resistors are not equal
Sir voltage at node A 10-(10i) ala aindii
simple , clear and right explanation! Thanks! Greetings from Paraguay
Which software use to create video ?
bro akkada dependent source sum lo ab terminals short circuit cheste 1kohm ,dependent source zero enduku aindi
Why was I1 = -1A in third case at 13.20. plz help
how did he get 10-10i for v in case 1, can someone explain?
Hey could you try this software? Bump into: 'Circuit Solver' by Phasor Systems on Google Play.
Nice explanation
Sir, @ 10:59 you've eliminated the
2 ohm parallel 2 ohm resistances to 2 ohm resistance.
But without making parallel formula how would it be 2 ohm?
It might be :
2*2/(2+2) = 1 ohm ??
If you closely observe, the 2 K resistor is in parallel with AB terminals (which are short-circuited).
That means their effective resistance will become zero.
And in the equivalent circuit, there will be only 5V voltage source in series with 2 K resistor.
I hope it will clear your doubt.
Please don't apply direct steps. It will be difficult to understand. If we have that capacity to understand that direct steps we don't need see your videos, we can do on our own.
Thanks God u understand that direct steps
amazing explanation
Hi please make video on Transfer Function of Electrical Circuits. Thank you, your videos are helpful.
I was confused but you did it wrong. Can you please change the value of Vab from 5v to 15v
I have a doubt in the case 1 to find R th u short circuited the voltage sources, but in the case 2 why you dint short circuit the 5 v voltage source??? Plz clear my doubt
Because in case 2, the circuit contains the dependent source. So, there is a different procedure for finding the Thevenin's theorem in that case.
Please go through the example, and after that if you have any doubt then do let me know here.
Simply superb
thx sir for good explanation
its 15V and not 5V in Case :1
really very helpful
I have a doubt. If the V in the final reduced circuit is thevenin voltage then how come the potential difference across A&B is thevenin voltage because as there is a resistance in series with equivalent voltage of circuit the voltage across terminals will not be the same as the equivalent V. Can you please elaborate?
It is the representation of the linear circuit. Or I would say using Thevenin's theorem you are getting an equivalent circuit, which has Thevenin's voltage source in seires with the Thevenin's equivalent resistance. And across that circuit generally load is connected. (Across terminal A and B of the circuit).
So, when you turn off all the independent sources and find the voltage across AB that's circuits equivalent voltage. It's not the voltage that you get across the load. Of course, it will be different. And it will be RL*Vth/(RL + Rth) . I think you got confused with it. Isn't it?
When u solve the problem if u hints the eqn very helpful 2 us....btw ur vedios is awesm and it is very helpful me in my study...tq
very nice section i liked it bro
Please upload this video again after modifying the vth value in case 1
What is this app?
You have calculated wrong value of Vth in case 1
I think it would be 15 volt
Hey Hemant, yes I have already mentioned that in the pinned comment.
you are great sir
i didn't understand why and how 1 ohm resistor got short circuited when A and B r shorted
When A and B are short-circuited, it offers zero resistance. So, anything in parallel to it will also offer zero resistance. Because all current will flow through the short circuit.
And that's why 1K resistor will also get short-circuited.
I hope it will clear your doubt.
Doubt about case1 Vab calculation
Yes I am talking about case 1 @ Vab
In case 2, why is the V used in the equivalent TH circuit 5 and not .5 as calculated at the beginning of the problem
It is 0.5V, Please check at 11:41 in the video.
Basic info is not available
How do you found Vab in first case (please respond)
Vab is the voltage between node A and B. Vab = Va - Vb. Node B is a reference node and is at ground potential. Therefore, Vb = 0. So, only you need to find the voltage at node A. The same has been found by applying KVL. I hope it will clear your doubt.
How u got vab man?
In case 1, since the points A and B aren't connected, why didn't we take the 10 ohm resistances in series?
Because we want to find the equivalent resistance across terminal A and B. What you are saying would be true if we want to find the resistance at some other point. Let's say the points where the 10V voltage source is connected there we want to find the resistance. In that case, both resistors would come in series.
I hope it will clear your doubt.
Then u apply kvl what about 20v
hi am a CE student....my lecturer wasn't that clear especially on obtaining the thevenin resistance....but lol...you made it simple sir..thumbs up!
He made a small mistake in example 1, but he already corrected it, I don't know why 99% of the comments are about that mistake? Let's just appreciate his effort instead.
You are so smart dude
Please add one more video about Norton's theorem
Sir...u said that Vab=10-10(I)....how u give value of A as 10 & B also 10?????
Exactely i too had that dought
If you see the left side of the A and B. There is a 10V resistor in series with 10-ohm resistor. Here Node B is considered as a reference node. So, the voltage between the two nodes will be the 10V minus voltage drop across the 10-ohm resistor. If I is current in the circuit then Vab = 10 - (10 ohm x I)
I hope it will clear your doubt.
At 9:58
Why A&B terminals were shorted?
To find the short circuit current through terminal A and B.
Please tell that why current source is replaced by open ckt and voltage source by closed ckt
In detqil you told it in vedio i cudnt understand it
In Thevenin's theorem, while finding Thevenin's equivalent circuit any source is replaced by its internal resistance.
And voltage and current sources which are used during the examples are ideal sources. Ideal current source has infinite input impedance and ideal voltage source has zero series internal resistance. That is why current source is replaced by open circuit and voltage source by short circuit.
I hope it will clear your doubt.
Is the test current in case 3...1amp...Same for all circuits????
Or does it changes???
well, we can apply the current source of any amplitude. But to make calculations simple, 1A current source is usually applied.
No need to take the current (I) amplitude as 1A. Take I Then Apply kcl then you should get the ratio if Va and I then that is thevenin resistance..... I hope my explanation was right.
Sir, Your channel is great!
Please explain more easily and give regular examples for B. Tech students
I didn't understand how to to find Vab in case 1 pls explain it....
Here node B is the reference node. (i.e Vb = 0V)
So, Vab = Va - Vb = Va.
So, we just need to find the voltage at node A.
And it is equal to 10V - (voltage drop across 10-ohm resistor)
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS thanks a lot
@@ALLABOUTELECTRONICS 1. is not Vab=Vb-Va, not Va-Vb Can you apply KVL in open circuit, since it is not a loop as point A and B are disconnected?
your lecture is very usefull and easy to understand🤓🤓
In finding vth y r u not calculating voltage at AB due to 20 voltage source?????
In this example, the motive is to find the voltage at node A, which is equal to the 10V minus the drop across the 10-ohm resistor. If we go further then there will be drop across one more 10-ohm resistor. But here we are not interested in the voltage after node A. If you start the loop from 20V voltage source up to node A then also you will get the same voltage. e.g 20V - (10) (0.5) = 15V. So, the point is no need to complete the loop here to find the voltage at node A. And you can start either from 10V voltage source or from the other end (20V voltage source), you will get the same result.
I hope it will clear your doubt.
Can u displace the formula for every example for every vedio then we calculate the example like can u keep the formula in brackets before the calculation then we can understand that this formula is used in this step if u put this we easily understand that this formula is used in this step
Hey Ravi, that's good suggestion. Yes, I will do so from now on each video. So, that you all can easily understand.
For you subtitle circuit Couldn't see clearly
At 10:35 why 3Vab is short circuited?
Vab is the voltage across the terminal A and B. When terminal A and B is short Circuited then Vab =0. And hence dependent source will also become zero. I hope it will clear your doubt.
Nice tutorial.
,By the way .....should we always use 1 A as test current in the 3rd case ?Actually,I found the value of Thevenin's resistance varied for other test currents.
Any value of current source can be used as test current. Based on the value, voltage across the current source will change. But ratio of V/I should remain the same. The advantage of choosing 1A current source is that, denominator is 1. So, calculation becomes easy.
Can you tell in which case thevinin and norton circuits are not equivalent
Norton's equivalent circuit is just source transformation performed on Thevenin's equivalent circuit. So, any circuit for which you can find Thevenin's equivalent circuit, you can also convert it into Norton's equivalent circuit.
only in complex circuits wih multilateral sources.remember it only works for bilateral and linear sources
How we get vab=5v how we use the formulae. Plz respond
Vab will be 15V. It's actually a correction. And I have already mentioned it in the pinned comment. I hope it will clear your doubt.
15V what youre doing?
In dependent source circuit how to understand I1=1Amp?
1A current source is applied externally. If you apply KCL at node A, then I1 = -1 A.
Can you please explain again why "short circuiting" the AB terminal in Case 2 ends up "short circuiting" the rest of the circuit as well?
In case 2, when we short circuit two terminals A and B, 1k resistor will be in parallel with short circuit (or ideally zero ohm resistance), hence the equivalent resistance of that combination will be zero. Now, as terminals A and B are short circuited, so potential difference between node A and B will zero or we can say that VAB=0. So, dependent voltage source 3VAB will also be zero. Now, again if you redraw the circuit then 2K resistor is again in parallel with short circuit terminal. So, it's equivalent resistance will be zero. And hence, eventually both resistors and dependent voltage source will get short circuited. And we end up with 5V voltage source in series with 2K resistor.
I hope, it will clear your doubt. If you still have any question then do let me know here.
EGG SELL LENT explanation. I understand it in the context of equivalent resistance! Thank you.
@@ALLABOUTELECTRONICS nice explanation
At 8:45 in case #2 while explaining Super node this stumped me Vx - Vth = 3Vth , You Jumped from Vx-Vth = 3Vab and equated Vab to Vth
how you write the 10-10i equation, please explain
What we need to find is the voltage Vab. B is the reference node. Therefore, Vb = 0. So, only thing which we need to find is the Va. That means Vab = Va - Vb = Va - 0 = Va.
Now, if we assume the clockwise direction of the current then Va is 10 V minus the drop acoss 10 ohm resistor. (Just apply the KVL upto node A). Therefore, Va = 10V - (10 x I).
I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS After all of the comments regarding this probem, this explanation makes the most sense as to what you are doing; however, how are you able to only do a KVL up to node A only? Vb may be zero, but what about the voltage betweent he 20 v and 10 ohm resistor on the right?
Thanks.
Sir how u have taken I1 as -1
The test current of 1A is applied at Node A. So, by applying KCL at node A, i1 = -1A.
A video for Norton's too!!!
Ι didn't understand case 3.
Vth=OV
But then we take Vth=1.2V in order to find the Rth.
Why?
well, that's not Thevenin's equivalent voltage. Its the voltage across the 1A Test current. In the circuit, when there is no independent source, the Thevenin's equivalent voltage is zero. What we can find is the Thevenin's equivalent resistance or impedance for such a circuit. And since the circuit does not contain any independent source, so we need to apply the external excitation either in the form of voltage or current to find the equivalent resistance.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS Thank you ,I have two more questions.
1.When there was a short circuit we said that the Rtotal of the pararrel resistor and the resistor of the short circuit is 0Ω so we removed it from the circuit(case 2) and therefore the voltage of the pararrel resistors was 0V .However ,the current 1A has a voltage of Vab=1.2 Volt?
2.In case 3 we didn't remove the 4Ω resistance that's pararrel with the short circuit ,like we did in case 2,and we didn't say the Rth is the 6Ω that remains in series with the dependent voltage source.(In case 2 Rth was the remaining in series resistance of 2kΩ)
..why?
Hello! I'm an ECE student, and I don't kind of understand how you got Vab for case 1
well, that is straight forward. First, remove the load across which you want to find the voltage.
Then find the total current that is flowing through the circuit(By applying KVL).
That current is -0.5 A.
Now, if you see, the potential or voltage at point A will be 10-(10*(-0.5A)) (Again using KVL)
And that will be 15 V.
Node B is at zero potential. So, Vab will be 15V.
I hope it will clear your doubt. And still if you have any doubt then do let me know here.
Ahh, I think I know where I got myself confused. See, in our physics class (where KVL was introduced) the arrows we drew were just loops, just really loops indicating the direction of, well, the loop we want to use KVL on - just a direction. And that had its own conventions. And now that I am in one of my EE subjects, the loops we draw are now mesh CURRENTS, they are loops (that provide direction for the KVL) and loop currents (or mesh currents) at the same time. And that kind of technique also has its own conventions. And somehow I kind of got them mixed. I don't know if I'm making sense, maybe I'm wrong, but now I understand how you got the Vab = 15 V with that understanding in my head (which again am not sure if I'm right or wrong). Anyway, thanks for helping me out! I really appreciate it!
If you find any difficulty in KVL, then you can check my video on KVL. It might help you.
bhai kya sahi banda hai gay for him
At 8:21 kcl lgate waqt last me Vx ki jagh Vth kaise le liye....?
Because there is a supernode in between. So, ignoring the voltage source in between, we can apply the kcl on the other side. ( At node A). I hope, it will clear your doubt.
For more info, you can check the video on super node.
Here is the link: th-cam.com/video/iIswDPKSQT4/w-d-xo.html
Why did u take test current 1A?
You can choose test current or test voltage of any arbitrary value. Just for the simplicity, I had taken 1A current source.
What if instead of 20v it is 20 resistance and not voltage?
I didn't get your question. Would you please elaborate a bit?
ALL ABOUT ELECTRONICS if you change V2 = 20 for R3 = 20 would you still do it the same way?
Sir in first sum Vab=15v sir
Sir, In 10.33 minutes, why the independents voltage gets short circuited.
Since the terminal A and B is short circuited, so voltage across terminal A and B is zero. And therefore, voltage Vab is zero. So, that's why that dependent source gets short circuited.
Sir, if the dependent source is current source in that case it will short circuited or open circuited?
@@nilakanta2555 If it is a current source then it will get open circuited. In this case, since it is a voltage source, so it is short-circuited.
Thank you very much Sir
Why Vab=10-10i
Best💥💥💥🔥🔥🔥🔥🔥