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By: Mehdi Sadaghdar
#ElectroBOOM101 #Lumped #Kirchhoff

Hi welcome to another episode of electro boon 101, where I will teach you electronics by over anything, my video to make it look even more interesting. I have covered a bunch of things so far watch them if you haven't, because slowly we are getting to a point where we can design stuff together. I have talked about resistors capacitors and inductors resistance and capacitance deal with electric fields, while inductance deals with magnetic fields. So one can model the entire electromagnetism using these properties.

Well, maybe not all of it, but close enough resistors resist against the current flow and convert the energy into heat, how a capacitor stores energy in form of electric fields between electric charges and can later release them. When a load is connected between Chamath and if you don't know how to use them, it will convert the energy into heat. Inductors store energy in the form of magnetic fields. Oh and yeah.

I guess every wire has a resistance to any other components in electronics, like transistors diodes antennas or transformers, make use of and manipulate these three properties one way or another. Now, let's try to learn how to analyze a circuit, and for that you must understand what a lumped model of a component is. Let me read you a passage from my electronic Bible lumped model. What is long model eventually Shall Perish those who don't use lumped model? Well, basically, the lumped model of electrical elements significantly simplifies the life of us, primitive engineers who would have to analyze complex circuits quickly.

Otherwise, you would have to resort to complex equations science and computing, which you can learn very easily using my sponsor brilliant there. You can learn tough concepts very easily using interactive courses and problem solving quizzes to make it stick in your brain, so go to brilliant org, slash electro ball we're the first 200 viewers get 20 % off and start learning like never before. But what is a lumped model? Have you ever been so sad that you felt like a lot as appearing in your throat? You could scream and cry, but because you're a caveman, you bottle up your feelings and take them to your grave with you where they belong and act like everything's. Fine lump model is the same basically in a lumped element model.

All sort of radiations from magnetic electric or even heat, are bottled up inside a component and don't leak out only the voltage and current are affected by the component. This makes life very easy because, if components, don't paddle up there and radiate stuff around, they start affecting the surrounding circuits, and this crosstalk between the components makes it very hard to analyze circuit behavior. For example, if a hot resistor gets close and warms up a transistor, the transistor parameters are significantly affected. If an inductor radiates magnetic fields, it will induce unwanted current in the neighboring circuit loops.

If electric fields leak from a capacitor, they can create unwanted voltage on neighboring conductors, and all these leakages make it very hard to understand the circuit behavior everything is lumped, no one is affecting anyone else, but the fact is, no component is truly lumped all components always Range and affect each other, but hey. We are not here to deal with black magic, so nothing will affect nothing, at least for now, until we grow a little bit more and with that, let's jump into two of the most important laws of electronics. First described by Gustav Kirchhoff Kirk of Kirchhoff yeah called Gustav called Kirchhoff's circuit laws. One is Kirchhoff's voltage, law or KVL, and the other one is Kirchhoff's current law or KCl.
You need to understand these well, because soon we will be designing circuits together. These laws are easiest to understand and work best when the components are lumped and nothing radiates or nothing else. So, let's start from there, Kirchhoff's voltage law states that in any closed loop of a circuit, the sum of all voltages cross components in that loop is zero and that's based on the law of conservation of energy and locked model makes it easy I'll talk about that. Later, according to my definition, KVL is not this: let's expand it a bit.

Imagine we have a circuit like this and I don't know the polarity of voltages across components, but I want to know their relations first. I assign polarities across the components. Any way I like one important thing you should remember is that it doesn't matter how you assign your polarities as long as you stick with them forever. You can't change them halfway or you'll have to start over.

For example, if you assign your voltage like this, but the actual voltage is positive, this way it doesn't matter the value you get for your voltage assignment will be negative, which is absolutely fine, so don't worry about it. Now, let's play a game of how many loops you see in this circuit before you say wrong, there is only three loops one. Is this big one one? Is this small one and the other one? Is this one? Now we have to start adding voltages in loops along one direction in a loop, it doesn't matter which direction you move through the loop. It can be clockwise or counterclockwise, but for fun.

Let's keep them all clockwise now moving through a loop. If you enter the positive terminal of a component right and positive voltage for it, and if you enter a negative terminal right and negative voltage for it like here, we enter negative v1. Minus v2 plus v3 is equal zero and make sure you write all the voltages in that loop in the next one. We have minus v3 minus V for minus V.

Five is zero and in the big loop we have minus v1 minus v2 minus V for minus V, five is zero and, of course, if you move the other way in the loop, all these voltages will be positive, which is the same thing and you have three Equations just like that, of course, these are not unique and from any two of them you can get the third one, because, for example, here two small loops make one B bloop so two optim-r enough and always go with the smallest one for ease or, for example, If you have a circuit like this and write KVL for the first one, you have minus V, 1 plus V, 2 is equals 0 or V. 1 is equal V 2. Similarly, in the second one V, 2 is equal to V 3, which means V. 1 is equal to V.
2 is equal to V 3. This is fantastic. It means that the voltage across all parallel components is always equal. Remember this.

So that's what you get from KVL, but those equations are often not enough to solve the voltage and current values and that's when you need KC according to KCl. If you have a bunch of circuit branches connecting in one node, the sum of all currents going into the node is equal to the sum of all currents going out. Otherwise it would mean that charges are accumulating in the node, which is impossible, minding the lumped model. Again, stay tuned for more clarification, it makes sense, doesn't it it is like if there is no leakage current, then all the water that goes into a pipe must go out of the other side.

Otherwise the pipe could bulge on it. Node and as we have defined that current is positive in the direction of the arrows again, it doesn't matter if you know the actual direction of the current you can assign them randomly for all. I care all these can point into the node, which would just mean that some of these currents would have negative values or the sum of all these currents would be 0 so based on KCl. If you have nodes with only two components connecting to it, which means they are in series, I 1 going into the node - is equal to I 2 leaving the node, or here the same I two going in is equal to I 3 leaving.

This is fantastic. This means the current through all series components is always the same. Remember these two. Let's look at this circuit.

It has four nodes: 1, 2, 3 & 4, but two of these nodes, don't matter because they put components in series and we already know the current through. All of them is equal, so only these two nodes are important for our analysis, so in this node I 1 going into the node is equal to i2 plus i3 leaving the node, and in this node I 2, plus I 3, going into the node is equal To I 1 leaving the node, which is the same as the first one and is not unique so here we only have one useful equation and that's what KCl does for you yeah. You can assign polarities and directions randomly, but it helps understand the circuit better. If you assign them properly, for example, start with your power supply, if you already know the polarity you put it on otherwise, for example, if it is AC put positive on the top side, then the direction of the current goes out of the positive of the power Supply and distribute through the load and splits in branches and returns to the supply and on the load side, the current enters the positive terminal of the load, so you can easily put polarities there.
This kind of assignment keeps your values positive for DC, not so much for AC, but using it will give you a better understanding of the flow of your circuit. Very simple. Now you know lumped model KVL and KCl. Let's do an example.

We have a circuit like this, with an 8 volt power supply and a bunch of resistor values like this and I've assigned polarities and directions. As you see, writing the KVL and KCl equation, we see in loop 1. We get this equation in loop 2. We get this equation and in this node we get that equation 7 variables and 3 equations, not enough, but we already know the relation of voltage and current in resistors, where, if the current enters a positive terminal, apparentiy store voltage across the resistor is a resistance times.

Current and just like that, we get four more equations. Now we just have to sit down and solve it. What your math requires improvement go to brilliant and start learning. Math click on the link now don't be intimidated by such a simple stupid circuit.

All you need is a little bit more information to be able to solve it even easier. For example, I know these two are in series, so their equivalent resistance is 1 plus 3 or 4 ohms, and this forum is parallel to that form. So the equivalent resistance here is 2 O and Ammi series with this one. So the equivalent resistance here is 4 ohms.

So this entire circuit is like an 8 volt supply across a 4 ohm resistor. The current going out of the supply is 8 volt, divided by 4 ohms or 2 amps. As soon as we know, I 1 V, 1 is 12 times I 1 or 4 volts right there from KVL in this loop we know. V.

2 is equal, 8, minus V, 1 or 4 volts and easy, as that we know I 2 is V 2 divided by 4 or 1 amp and from KCl we know leave the rest to you that first bit about equivalent circuits was important. I should just tell you how series and parallel stuff work, but I won't because we already have much information to digest. I will make a video later about equivalent circuits and that will help you simplify the circuits for analysis, but for now KVL and KCl are enough. As long as you have lumped model elements, but what, if you don't what? If the stupid elements are real and leaked radiations around some people, even argue KVL and KCl don't hold in such cases.

No, let me put your mind at ease. Kvl and KCl always hold as long as you have your definitions straight, but they only give you results as accurate as your model, so you have to know every single elements, that's affecting your circuit. For example, imagine I have a loop like this: an AC supply across a resistor. I measure the voltage across the resistor and it doesn't match the supply voltage.

What the hell, the reason might be: another inductor radiating magnetic fields through my loop, creating voltage. So I must understand there is a missing element in my model that I didn't consider and that's the loop inductance acting as a secondary of a transformer I put it in and the KVL holes like. I battled it out in one of my old videos and imagine you have AC current going into a node and going out of the other side, and you expect both to be equal. You measure and they're.
Not. This means there must be a third current leaking out somewhere, but where maybe your wire is running too close to ground and that creates a stray parasitic capacitance between your node and ground. You didn't account for and is sucking the current away. So as long as your model is accurate, KVL and KCl are accurate and all this nasty happens in AC, where you have most radiation in DC, you only have to worry about Heat and that's pretty much DC changes so slow.

Now sometimes these stray parasitic components are so many you ignore the ones with negligible effect and only include the ones with the largest effect in your model, which is fine in electronics or any engineering. We define an acceptable inaccuracy for our application and design our circuits to work with that tolerance. So don't worry about things so much. We will design simple stuff together soon.

It requires very simple math, but if you're worried about your math level go straight to brilliant org slash electro boom there, you can take mathematical fundamentals. These look quite fun. Brilliant is filled with very well-made courses on math science and computing from basic algebra to quantum computing, but, most importantly, they made it super fun to learn with their interactive platform. Are they mean? No, I'm not interactive.

Did you know that you can also click here and give the brilliant membership and the treasure of knowledge to someone else? Do it down so go to my link and sign up for free and you'll have access to tons of free stuff already, but the first 200 people to use my link will get 20 % off of the annual Premium Membership for full access, and you could call Yourselves, big brain and thanks for watching.

14 thoughts on “LUMPED MODEL, Kirchhoff Circuit Laws (ElectroBOOM101 – 008)”
  1. Avataaar/Circle Created with python_avatars MrDDaye says:

    Why am I watching this? I am an electrical engineer. You're just so damn entertaining!

  2. Avataaar/Circle Created with python_avatars SuperHamSniper says:

    medhi at the start of the video going through how to hurt yourself with every type of load

  3. Avataaar/Circle Created with python_avatars Wolf6774 says:

    I learned those as “Mesh analysis” and “nodal analysis” , but this pretty much sums up everything lol

  4. Avataaar/Circle Created with python_avatars Looking In With Victor B says:

    With the reference to your Bible, I was going to ask if you're going to publish your own UGLY little book, but then I watched a minute later realized that the Lumped Model actually is the kryptonite to ghost hunters and mediums.

  5. Avataaar/Circle Created with python_avatars Pavel Jelínek says:

    Please make a similar video showing the current flow in a battery-fueled circuit.. i've read a many forums and people simply can't get to agree of how does the current flow in that circuit and how does the electrons flow inside a battery (well i personally think that there is no flow of current inside a battery because there is no closed loop in it but i think that the negative therminal pushes the electrons to the positive terminal so they come out from the positive therminal to the loop/circuit when discharging and coming back to the negative am i right?? But that leads us to the next question, how can electron go through a negative and inside to the battery? That is impossible, leads me to think that there must be a positive and negative side of that negative therminal so the electrons go inside battery through the positive side of the negative therminal, right?) And the charging worx exactly the opposite way? I would like to make it clear..

  6. Avataaar/Circle Created with python_avatars Sarthak Bathe says:

    Hi sir i am from india and i am in high school and this video helped me alot to understand KCL and KVL
    The way you explains the concepts helps us to understand it easily 🙏

  7. Avataaar/Circle Created with python_avatars Infinity Games says:

    This is good stuff. Now, can you skip to MOSFETs and amplifiers? COVID screwed those classes for me.

  8. Avataaar/Circle Created with python_avatars Sven Bosma says:

    I have an exam next friday and it is about oscillator circuits with capacitors and inductors. I don't understand anything yet and only have 2 days left to learn…. Let's hope electroboom speeds up his editing 🙂

  9. Avataaar/Circle Created with python_avatars Drake Tamer says:

    Alright so I'm back again, and I've just realised an issue with lumped models. If in a lumped model nothing radiates and messes with other stuff, does that mean that, given our lumped setup, radio transmission is impossible? Now there's a thought to keep you up all night >.<

  10. Avataaar/Circle Created with python_avatars The Unboxing Authority says:

    Put a capacitor at the node, and then it can be higher than the power going out 🙂 until it escapes.

  11. Avataaar/Circle Created with python_avatars Jay Eifler says:

    So no free energy. Your debate with lewin makes me want to know about this 'radiant energy' of master ivo. What is the longitudinal magneto dielectric wave? If such a longitudinal EM wave is to exist what are it's implications theoretically? Somehow we must be assuming that the interpretation of maxwell's results have yet have this result shown or derived form it: that is longitudinal em wave exist as some mode of energy transfer that becomes significant under certain conditions. Ivo uses these bifilar inductive coils (tesla?). Can you replicate these results? Is there some measurement I'm missing that shows this energy?

  12. Avataaar/Circle Created with python_avatars 邪王真眼りっか says:

    Now I understand better in KCL/KVL than last year when I have my electronic course …

  13. Avataaar/Circle Created with python_avatars Tom Risely says:

    Could you do a video on where you can and cannot connect oscilloscope probes? Like how to connect them to mains sources and how to connect to circuits without damaging them?

  14. Avataaar/Circle Created with python_avatars AlexnderPlotnikov says:

    I am teaching electrotechnical basics in the same way. I am glad to know that our school is similar in a lot of ways. Thank you)

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