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Added: 2026-05-31

[00:01:34]Hello friends, welcome to the online platform of Youjus Academy. Today is your second day. Okay, so yesterday we started our Electrical Circuit and Network or SECOND i.e. Circuit and Networks subject. Yesterday we saw many basic concepts which are important for us in this subject. As we are going to continue it in the same way, and in the future, wherever we solve numerically or whatever circuit we want to analyze, we will need all these concepts.

[00:02:05]Okay, so yesterday we saw that. Okay, after that, we started the first point which is our first chapter, Basic Circuit Elements. Okay, in it we saw many definitions like loops, then nodes, branches, then today we will see mesh.

[00:02:22]Okay, so we are going to continue it.

[00:02:24]Today we are looking at the fourth definition, i.e. what is mesh? Now you know that this mesh and whatever loop is, both are equal to you. It may seem ok but there is a slight minor difference between them ok we differentiate it with a slight minor difference i.e. if you look at the loop then you see the multiple of the loop we see this multiple circuit how can we call it a loop we form loops of different types then we look at each condition it is a red loop ok what is this redundant if we have already formed two loops in this circuit then we don't need to consider a next loop ok that means by considering that but what is there any work i.e. simple term we can say simple term is not of any work ok now this which was in red color ok so this loop is not of any work because we have already formed normal loop i.e. whatever our actual loop was then there is no need to form third loop here i.e. what is it redundant loop now you will see this loop and mesh are absolutely equal but there is some minor difference between them There is a difference, now let's check if it is a minor difference, but before that, let's see what a loop is, what a closed path is, what a closed path is, a circuit.

[00:03:43]Look at this, in this way, we have a circuit.

[00:03:45]Now, this circuit has started to form in this way. Then what we do is we can say that we are drawing multiple options. We are drawing options that this can be a loop form. Then this can be a loop form.

[00:03:58]Or next, look at this circuit. In this circuit, we have formed an actual loop which is the shortest and a long one. Okay, the longest loop has been formed. That is, we can do this condition. That is, we are drawing a possibility. How can that loop be formed? After that, look at this here. What do we do here? Alternate it. That is, reflect it. Okay.

[00:04:19]Then now, look at the mirror image of this. If we draw this, this actual loop has been formed here and whatever the longest loop is, it has been formed like this. Okay. After the condition has been done up to this point, this is what is this different loop. That is, two actual loops. The loop is done, so there is no need to form a third loop here, so what do we do here? We call it a red loop.

[00:04:36]Okay, after that, look at the mesh. Now, what is the mesh? Okay, what is the loop that does not contain any other loop?

[00:04:44]Win it. The small possible closed path. What is the small difference? Now, look at what we were doing there. We were also drawing a small difference. We were drawing a small path.

[00:04:59]Whatever current is going to flow, like if we draw a circuit here, I suppose I have a circuit of two loops.

[00:05:08]Now, we are not putting elements in it right now. We just need to visualize it. Now, what we did here is draw two boxes. The circuit is drawn.

[00:05:16]Now, what we do here is form a loop like this. This is a loop like this.

[00:05:21]Right, what we did here is a shortest. Both. But what is the shortest loop formed? Another suppose. What I did is form a short loop and form a long loop. Okay, what we are doing here is both the short and long ones.

[00:05:36]Or a little more modification in this, okay, now suppose I form a long loop, that is, these two normal loops that I have formed are all short, okay, after that, I form the longest loop, that is, what else will I do, I will make it long, that is, what does this mean? We see the possibility that how many loops can be formed in that circuit, okay, short or long, okay, we look at it in this way, but what is in the mesh, the shortest path, that is, what is the shortest path or closed loop for that current to flow, that is, we see there, so we will learn everything that is going to be learned later, mesh analysis, okay, what do we have to do next, we have to do mesh analysis, that is, we have to do mesh analysis, that is, we have to do mesh analysis, what do we do there, we put the mesh in mesh analysis and we do mesh analysis, that is, what do we do, we see the shortest path there and we do the same analysis, so this is the term that we will need later, so we need to clear this term, what is the difference between loop and mesh? Okay, so let's see what you say, the closest loop is okay, what is the closest path, I mean, suppose I have a voltage source here, okay, there is an energy source, what is going to happen from that energy source now, now everything is closed, okay, what have we taken, here we have taken three closed loops, what do we do with all of them, we take the shortest, we take the shortest part of all, now what is the shortest path for, suppose here is a voltage source, now what is going to happen from this voltage source, a current is going to come out, what is going to come out, a current is going to come out, then whatever current is going to do, what is going to do, positive to negative, what is going to do, positive to negative, then what will happen at this point, see this current flows from here, then this closest loop is formed in this way, it will go from here to here, okay, it will come to this node, and from this node it will now take the shortest path.

[00:07:39]Where is the path, what will it do, will it go downward or will it go here? Because from here it has the longest path. Okay, what does the longest path and current do? But we look at the shortcut path, that is, if the shortest path is the shortest path, we see that as much as possible flows from there. So now, where is the shortest path from this? This is the shortest path. So, we have three loops. In three loops, we can form three meshes. Okay, so what have we done here? Here, we have formed Iv.

[00:08:07]What have we done? I1. That is, now there are three loops. Three currents are going to pass here.

[00:08:12]Because what is going to happen through each element?

[00:08:14]Current is passing. So, we have formed three currents here. In each mesh or loop. Okay, we cannot call a mesh a loop.

[00:08:23]Okay, look, now we cannot call a mesh a loop, but we can call a loop a mesh. Is there a small difference here? Okay, let's see. Here, we have formed a next loop, that is, a mesh is formed.

[00:08:36]After that, here, but We have formed a 3, that is what is the difference between loop and mesh. What is the loop?

[00:08:48]What is the possibility of short and long closed paths?

[00:09:03]Okay, so what is the loop? What are the possibilities? We are looking at how short and how long is the closed loop in this way.

[00:09:10]And after that, what is the mesh? We are just looking at how short and how long is the closed loop. What do we do?

[00:09:13]We identify the shortest path. What do we do? We identify the shortest closed path.

[00:09:21]Okay, so we are forming this in this way.

[00:09:24]Then, let's see for instance in a rectangular circuit vs. four registers. A rectangular circuit is a mesh. Okay, now suppose we have made an assumption.

[00:09:35]What do we have? We have a rectangular circuit and what do we do in it? We have formed the circuit in this way. Okay, now I have four registers here. Four registers. Now, what do you do here? Here, we are forming a closed loop. Okay, now, what do we do here? Here, we are forming a closed loop.

[00:09:50]Now, what do we do here? Let's consider a voltage source.

[00:09:53]Okay, now.

[00:09:56]If we consider the voltage source here, look here, is the entire circuit closed and what is happening here because the circuit is closed? Is current flowing? So what happened here?

[00:10:06]I have drawn the shortest path, the mesh.

[00:10:08]Suppose there is a circuit on this side too, OK, if there is an additional circuit, if there is an additional register, what would we have done here too, if we had formed a loop or if we had formed a mesh, if we were to form a loop, then I would take the longest path here and if I had to form a mesh, I would form it directly in this closed loop, that is, I And what we see while forming this is the direction of current, OK, so suppose here we come across two conditions, suppose let's see, suppose let's see, here there is a voltage source, what is the positive polarity on the upward side and the negative polarity on the downward side, that is, what is the current flowing from positive to negative, what is the current flowing from positive to negative, that is, I can do this direction like this and what is in the mesh, if we give one to one the direction clockwise or anti- clockwise, then what do we have to do next, continue in the loop like this There is no such thing as a form in which we can give direction based on our own calculations. OK because in the loop actual we see how the voltage source is OK now suppose here this direction form is in the image which is clockwise direction but what is here positive direction is on OK positive polarity is on top and negative polarity is on down side that is how current can flow there in actual then in such a way where is all this possible then in the loop condition but in the mesh what do we do here suppose here V2 voltage will be less than what will be 2 voltage will be less than 1 then what do we do in that condition we see whatever polarity is greater or whatever voltage is greater and according to that what do we do start giving direction to it then what did I do then compare what is 2 which is less but V1 which is greater then what did I do there I considered I1 this clockwise The direction then gave everyone what we did clockwise clockwise direction OK so in this way this is the same difference and this is the explanation OK so if anyone has any doubt then everyone has understood what we did clockwise clockwise direction OK so in this way this is the same difference if you have any doubt then tell me in the chat box sir if you don't understand then I will repeat it again but clear the concept because you will need a lot of concepts in this subject which I have already cleared properly for you if you don't understand then ask again OK I will tell you again I understand tell me in the chat box well once explanation OK so in this way this is the difference explanation OK so in this way this is the same For those who do n't understand any doubt, let's see the next definition.

[00:13:46]So what is the next definition?

[00:13:48]What is an active network? Now what is an active network? Let's see what we can call an active network and what is an active network. So an active network is a circuit that contains only one source of energy called an active network. That is, what is the assumption that we are forming a circuit that we want to analyze or solve?

[00:14:20]We are looking at a circuit of this type. So whatever circuit we want to solve or analyze, what type of network is it? Is it an active network or a passive network?

[00:14:30]Then how will we know this difference?

[00:14:33]If we say that an active network is in it, then how will we say that it must have at least one source, be it a voltage source or a current source, that is, it runs regardless of which energy source is it, either a current source or a voltage source. At that point we can call it an active network. Otherwise, it will be a passive network. It has different elements in a passive network.

[00:14:58]But if we need a main element, then a voltage source or a current source. If there are one or two or three more, they work, but if there is at least one voltage source or current source, then what should we call that network? Active network.

[00:15:16]Voltage source and current source are the active elements. Okay, so the active element is called an active element. Because what it does is it supplies whatever we are forming the circuit, that is, you see this circuit or now we have drawn this simple circuit.

[00:15:39]Look at it.

[00:15:41]Now, what do I have to do to supply this register? Supply means to actively charge it or supply it. Okay, so now what do we do to provide that supply? Voltage source is added to it then what is this circuit what is active network what is active network or active circuit you can call it circuit or network ok so what happened our active network then active network form or it has to be created then how can it be created then it should have at least one voltage source or current source in it any energy source runs then what can we call that network active network ok which is called active network then ok so far we understood the difference that it should have some voltage source or current source after that look passive network now now next definition which is our passive network now what will be passive network then now here we know that if there is voltage source or current source then active network i.e. what is the opposite of it if it does not have voltage source or current source then if it does not have voltage source or current source then we will call that circuit What can we call a passive circuit or a passive network? Okay, then look at a passive network. A network that does not contain any source of free energy in it. Okay, what is being said here is that a network that does not contain any energy source, does not contain any EMF source. Okay, then what can we call that network? Passive network is called a passive network.

[00:17:18]Now to form a passive network, then we have to form a circuit. Then what type of elements can we connect there?

[00:17:26]If we neglect only these two and ignore the voltage source and current source, what can we do?

[00:17:31]What can we call that circuit? Passive network?

[00:17:33]Then what do we need to form a passive network?

[00:17:34]True, resistors, inductors and capacitors are the passive elements. Now, they cannot produce anything by themselves. What can we do? Now, let's talk about a little difference between a passive element and an active element.

[00:17:47]Suppose the source is a voltage source. It is clear now which circuit are we analyzing now then while analyzing we put voltage source or current source there then suppose there is voltage source or current source now what is between them if we say voltage source then there will be voltage if we say current source then there will be current so what should I do with them now suppose we take a battery then if we take battery then what will be in the battery both voltage and current but what I am doing here is splitting both of them voltage source and current source then now we get output from this voltage and output from this current then now what do we have to do to give output to them first it has to charge like say your battery is a mobile battery what do we have to do to it if we are using it then we have to charge it first then after that we discharge it throughout the day then what do we do to it in the form of charge what do we do to it voltage and current then it returns in our return But what gives voltage and charge but we have split both of them then if this gives us voltage as output then what does it take as input and if this gives us current as output then what does this input take current source right that is what we can say in simple language that in the form in which we put energy in ok input input we get it in output i.e. what is giving voltage here and what is getting in output voltage and current given in current source and what is getting in output current i.e. in the form in which we provided energy there we get it back then what can we call these active elements and what element included in that circuit is included in that circuit what will we call active network i.e. what do we do from active elements active The network is forming, clear up to this point, after that, the passive network, now look at the passive network, why are they called passive elements? Then now what is the meaning of passive element, what does it do? It ingests energy, what does it do? It ingests energy and releases it in another form, that is, look here, the input is the same, the output is the same, but there is nothing like that in the passive element. What is happening in the passive element, so let's see what each register is, what is it? Suppose I have taken a register, OK now, suppose what happened to you, this concept must have been done in F-double, but if not, we are clearing it, so I have taken the register here. So now, what do we have to give to the register? Suppose, a single circuit is formed here, as in this way, a voltage source is given here, but we connect the register, now what will happen from here? Since a closed loop is formed, current will circulate or current will flow through it, then when current is flowing, what is the register?

[00:20:49]The current and voltage that it does, i.e. Ila means power I means what is our power What does it do It takes energy and converts that energy into heat energy What does it do in heat energy You should have seen a grate in the house now What is the electric grate in it Whatever is its wire OK Spring type Whatever is the wire What is the wire made of High resistive material That is, there is complete resistance used So what do we do We give it a supply That is, power circulates through it If both voltage and current meet it Then what does it do After the current circulates through it I Sr R loss What does it do I Sr R loss I Sr R loss What is our heat loss What is heat loss That is what is it doing Voltage and current In what form is it taking Intake Voltage and current Input Aj Input What are we giving it Voltage and current But what does it transfer it into So Aj A Heat energy And heat energy i.e. what is light energy But we can say that from heat energy we can also get light energy, whatever the LED in our house is or a bulb, okay, whatever yellow bulb was, what was that yellow bulb made of? From the resistive material, then from that resistance material, what happens when voltage and current pass through it, then what happens immediately, there is loss in it and heat is generated and that heat energy is consumed as light energy. Okay, then resistance is work, so what do we call it passive elements?

[00:22:24]Clear, they take energy in the form of voltage and current, they ingest it and release it in the form of heat. Clear, up to this point, after that, let's see what an inductor is, now what does an inductor do, but is an inductor a passive element? Now let's see the function of the inductor itself, how do we denote an inductor by L?

[00:22:44]Okay, we denote an inductor by L. Now, whatever circuit this is, everything is given in it, resistor, inductor and capacitor.

[00:22:51]Then see In which form is the same energy going to go into the intake v i ok voltage and current we are giving aj a input energy only what it is doing is converting it into a different form i.e. aj a energy conservation is doing conversion ok what is it doing is converting it into another form then what is it converting now what will it convert voltage and current into then it will do in magnetic flux which we denote by fi what will it do in magnetic flux what will it do voltage will take current i.e. as the current circulates what will it do in that coil what will it release the current in form of flux ok or you in your college you had also done an experiment in school also if that experiment was done then what do we do take a toy take a nail and what do we do on it take a coil wound take a wire of copper and it After wounding, he is given a battery supply, then what does he do immediately? He behaves like a magnet. What does he do? He behaves like a magnet. So how does it behave as a magnet? If we convert the voltage and current into what form through the coil, it is converted into what form. If it is converted into the form of a magnet, then the flux is generated there. Then what is the work of the inductor itself, that is, what do we do to the conductor by winding it, what do we do to convert it into an inductor?

[00:24:16]Then what does it do to produce the flux there and what is there in the conductor as well? There is magnetic flux, but what are they, they are absolutely negligible, that is, they are in a very small amount that we do not feel, but as soon as we wind it in the form of a coil, then what happens immediately? We can call it a powerful magnet or a strong magnet, a strong magnetic field is created there. Okay, then what is the work of the inductor?

[00:24:42]Converting the voltage and current into the form of flux. Okay, now what do we call this a passive element, then a capacitor, now a capacitor, but what? The passive element has come, so now what does it do? Look, whatever is the input, it is voltage and current, it will only give us a different form in the output. Now what is it going to do?

[00:25:01]We have taken a capacitor, we have given it voltage and current, then what will it convert into? Then what will it do in the charge? What will we do here? We have converted it into the form of charge or what is the capacitor doing? It is converting it into the form of charge.

[00:25:17]That is, what are those two plates installed here? Let's see, two plates of the capacitor are installed, as we have given it a supply, OK, we have given a voltage source and applied it. After that, from here, positive means positive charge will accumulate at one place on this plate and what will happen to negative means negative charge electrons, if they accumulate on one plate, then what are these two different charges? Positive charge and negative charge are separated out and stored in the form of charge and at the output, we also get the charge.

[00:25:51]In the form, the capacitor takes voltage and current as input and converts it into the form of charge.

[00:25:59]Okay, so all these basic concepts are required for you. Now, if you are from MSBT, in MSBT, you need to clear this register, capacitor and inductor in the very beginning. So, you already need to clear this. For those who are autonomous, what are DC circuits?

[00:26:17]Okay, then what do we want to see in that DC circuit? We have to see the register.

[00:26:21]But what do MSBT children do?

[00:26:26]What do they do with these three? Register, capacitor and inductor? Then you should know this very well. Okay, if you are facing any problem, you can tell me in the chat box. Okay, I understand till now what is active network and passive network. Let's see, let's move on to the next definition.

[00:26:44]So, what is unilateral and bilateral network? What is unilateral and bilateral network? Now, what are unilateral and bilateral networks? So look, these two are opposite to each other, just like we saw active network and passive network, same type of unilateral and bilateral, now unilateral means what is unidirectional, simple word, let's convert it, unidirectional lateral means direction, why is this unidirectional, now what is unidirectional, suppose we have taken a circuit, now in the circuit we are seeing unilateral, so what do I do here, here I have taken a diode and what have I done to it, a voltage source has been applied, clear, then now unilateral means what if the characteristics, response behavior means what characteristics will it behave, when will it behave, when will we give it a supply, then what will it behave, in what way will its response be, then what will be our characteristic of the network dependent on the direction of the flow of current, that is, its element, ok, which direction will it The current will flow and in which direction it will not flow, then this shows its characteristics. Okay, then the network is called unilateral. Then what do we call the same network? A unilateral network is called clear or unilateral. We can also call it elements. Then what comes in it? Diodes come and transistors come. Now let's understand this from this diode.

[00:28:31]Now look, you know that our diode has two terminals, a node and a cathode. Node and cathode. When you study FO, which is the subject of Fundamentals of Electronics, you will know that we do forward biasing and reverse biasing in it. Then what is forward biasing and reverse biasing? When we connect the battery supply, i.e. the positive terminal of the battery is connected to the node and the negative terminal of the battery is connected to the cathode of the diode. At that time, what will happen will be in bias, that is, at the same time this current will flow here. We took our normal diode, our PN junction diode, P junction. If we take the diode, then when we apply the positive supply to the node, whatever is the negative supply, to the cathode, at the same time what will happen here, current will flow, that is, forward bias, then at that time if current flows, that is, in what direction, now we know that if we apply positive here and negative here, current will flow only.

[00:29:36]Otherwise, what will we do? Now let's change the negative supply. Okay, let's change the positive and negative, that is, we will connect the positive terminal to the cathode of the diode and the negative terminal to the node. Then see what will happen at that time, what will happen here is reverse bias. What will happen is reverse bias, that is, a sufficient voltage, what will we do? What will we do? We will give it sufficient voltage, that is, we will give it voltage up to its limit. Otherwise, if we go beyond its rated value, it will circulate reverse current, that is, leakage reverse. It will circulate the current and what it will do is it will start circulating the current but what we do is we supply it up to a specific limit or we apply the current now see whether this current is going to circulate now or not because we have changed its polarity, we connect the cathode to the positive terminal and the node to the negative terminal then what happens to this condition is it shifts to reverse and current will not flow in reverse bias ok current will not flow in reverse bias so what is it that we notice here is that whatever is going to operate in what will operate only forward bias what forward means that current will flow in one direction current will not flow in the other direction because we have changed the polarity there so what is this we call unilateral network ok unilateral network means what is this that shows that its only one direction what one direction current flow in one direction only one What can we call direction?

[00:31:13]We can call it one direction. Okay, so what can we call it? We can call it a unilateral or unidirectional network or we can call it elements. If we place this in a circuit, what will we call it?

[00:31:25]Unilateral network.

[00:31:27]Clear. Let's go to this point. Let's see what the next bilateral network will be. Bilateral network. Now, if we change its elements in a bilateral network, we mean that current will flow in both directions.

[00:31:54]If we place an element in it in that circuit, what will happen? It becomes a bilateral network. Then see if the character's response and behavior are different.

[00:32:04]How will the response and behavior of the network be independent of the direction of current? The element means that it is independent. It can flow in any direction.

[00:32:17]Okay, what was happening here? It was dependent on one direction.

[00:32:20]What was it doing on the other direction? The current was not flowing.

[00:32:22]Okay, but what is it independent of?

[00:32:25]Which direction? Current can flow in either direction or through it.

[00:32:29]Okay, this is an element called the network called a bilateral network. What is our example of a register? Let's see what we did. We put a positive terminal here and a negative terminal here. Will current flow through it? Because what is the flow of the circuit and which element is this? It is a bilateral element. Okay, whatever network is forming a bidirectional register, that is, it can flow through it from both directions.

[00:33:09]You give it from here or give it from there. It is a bidirectional element. So current flows through it from both directions. So how do you supply it? If it is a closed circuit, current will flow. Okay, if it is a closed circuit, current will flow there. If we change its direction or change its polarity, what will happen?

[00:33:29]Current will flow through it. The direction will now change. The current was previously anti- clockwise. Now what about the next one?

[00:33:37]Clockwise direction is done, what is this bilateral network? Is it a bilateral network or bidirectional? These elements are branches, but we can say clear. Up to this point, we can also say that the inductor is also a bidirectional element. Then the capacitor, the capacitor does not have any polarity, where we put the polarity, it will automatically carry the charge. Okay. Then the inductor, in which direction we make the current flow, only what will happen is that the flux produced will change its direction. Okay. So this was a bilateral and unilateral network. Okay, so up to this point, we had basic definitions that we would use later or see its concept. Next, we will solve the network. Clear up to this point. Okay, let's see.

[00:34:29]Now, let's see the next condition. If anyone has any doubts, let's ask.

[00:34:33]Okay, otherwise, let's continue. Let's see what is your question, what is between an active network and a passive network?

[00:38:59]Now then there is a difference between active elements, I will tell you what an active element is, which is a circuit in which a voltage source and a current source are present, we call it an active element. What are both of these? An active element is a circuit in which an active element is present, so look, this is an active source or a circuit.

[00:39:28]Look, what are we doing here? We are forming a circuit. Look, what are we doing here? We are forming a circuit.

[00:39:33]Okay, now what is this circuit? Is it passive? Is it passive? Because I have only added resistance to it, and resistance means what is a passive element.

[00:39:43]When I add a voltage source or a current source to it, or is it already dead in it, then what can we call this network?

[00:39:53]Active network, because what is there in it? Is it an active element? That is, what is this active network?

[00:39:59]Okay, and passive element means what is only in it, resistor, inductor and capacitor. Present means those which take energy in one form.

[00:40:09]What to keep in mind in simple terms is that they take energy in one form and release it in another form.

[00:40:13]As mentioned here, voltage and current will remain as input of all three but in the output we will find heat at one place. In the resistor, flux will be found in the inductor and charge will be found as output in the capacitor.

[00:40:24]But is that going to happen in a battery?

[00:40:26]What will happen in a battery? Both voltage and current will be found, that is, input but they will take it and output but they will take it only. Okay, for example, whatever your mobile or any electronic gadget is which is battery- powered, what do we do, we charge it, that is, here we give them voltage and current, that is, what can we say, we are giving it power, then what do they give as output? They give power only.

[00:40:52]Okay, input power and output also provide power, that is, in that battery it is converted into chemical energy but what do we get as output? We get only voltage and current. Okay, so what do we call this element, active element, and if active elements are present in that circuit, then we call that circuit an active circuit or active network. Clear up to this point in short we can say that the element is active element we can call that network active network and in the circuit which does not have voltage source or current source or energy source we call it passive element or passive network Clear up to this point let's see now next concept let's see for a minute understand if you have any doubt up to this point ask ok then now let's see we became passive active un passive doubt clear now let's see what open circuit and short circuit are open circuit and short circuit so open circuit now what are open circuit then see in this case here what we do here we are drawing a circuit in which we have taken voltage source and current source current source or voltage source ok and what we have done here we keep it open what we keep open means here point A and here point B is formed like this now we have taken circuit now is this closed or not as in mesh and loop we I said OK if it is closed then current flows OK now look at A and B point A and B what is it open is it connected to each other is it not directly is there any connection between them or have we placed a wire here with a solid wire or not so there is no connection between them then what can we call this circuit open circuit can we call it open circuit because here A and B are directly connected is it not there is any element here so what can we call this circuit open circuit clear OK simple concept is open circuit and short circuit OK so whatever resistance there is what will be whatever resistor there is if we look at the complete electrical parameters now we have to apply all these concepts resistor inductor then whatever resistance there is in the open circuit now we are imagining here that there is some resistance then that resistance also has some value now the value of resistance I will tell you Ohm's law It was said that according to Ohm's law, we have one thing that current is inversely proportional to R. That is, when the resistance is high, it is increasing, then the current will decrease, and when the resistance decreases, then the current will increase.

[00:44:24]That is, the value of this resistance is high somewhere, so the value of this current is low. Okay, I understand this far, but what is the problem here? The circuit is open, there is no closed path, so will current flow? No, we have put everything in the circuit, voltage source or we have connected the resistor in it, but what is there in it, does the current circulate because it is not a closed loop? We need a closed path to circulate the current, then it is not a closed path, that is, what can we say here, what is the value of the current, the current flow in the circuit is zero ampere, what can we say, zero ampere, now when will this zero be, well, we have to put a simple concept here, this zero, so we consider it as a constant, we take one by one here, now what will be the value of the resistor, if this will be zero, then one by infinity, if I consider, what will be the value of this, we will find zero, will we find zero, will we find zero, that is, the value of the resistance is infinity, and since it is infinity, the current is not circulating here, okay, now we are talking about electrical parameters. If we look at what resistance is present here, what is its value? It is infinity, so infinity, if there is resistance, then current will not circulate.

[00:45:44]What do we call this circuit an open circuit? Okay, so in its connection, we do not see any direct contact, okay, it is called an open circuit, no physical contact between A and B points, so what can we call an open circuit?

[00:46:30]Because it does not have any physical contact, whether it is a resistor, inductor or capacitor, or a solid wire, but there is no connection between them? Okay, so what can we call that circuit? Open circuit.

[00:46:43]Then what is the current in this circuit? Zero flows and what is the value of resistance? Infinity?

[00:46:47]Infinity?

[00:46:50]Clear, but keep in mind that what voltage will we find in an open circuit?

[00:46:56]I am measuring the voltage here. What am I doing? I am measuring the voltage here. So across this, I get the voltage I need. Suppose we will consider the fault here.

[00:47:06]Okay, now when I measure here, across these two points, point A and point B. Okay, what was here, if I measure the voltage here, I get a fault applied here. Okay, I get a fault. That's what I'm doing. If I measure here, I will get a fault. Okay, I will get a fault. Now, how will I get that fault?

[00:47:28]Look, at one point, we saw a series-parallel connection. Okay, at the beginning, I had made it clear to you that in series and parallel connections, voltage and current are different. We saw that in series, the voltage will be different across each resistor, but if the current is the same, and in parallel connection, the current will be different, but the voltage will be the same.

[00:47:54]Clear. Now, if a resistor is connected in series, we will get a fault here. It meets and the same meets here too, so it is connected in series, right? But how do we meet it? There is a concept behind it. So, what is it? Ohm?

[00:48:12]Now, what do we call it?

[00:48:19]What do we call it? Voltage drop? Now, how can we call it? Voltage drop? So, what is it? F is V. Now, this fault occurs when we have to do voltage drop through this resistor, that is, n2 R. When current passes through this resistor, at the same time, there will be a voltage drop here, but what is the circuit open? For example, now the value of the resistance here is 10 ohms but what is the current? Then the current is zero, then the voltage, what do we do with it? We multiply it with the resistors, then what will we get as the result? The voltage will also be zero, that is, what is flowing through it? Zero current is flowing, that is, the value of the resistors, but since it is multiplied there, it also becomes zero, so what will happen to the voltage drop to zero?

[00:49:00]That is why the voltage that is found here is found here. Clear, so in an open circuit, we have such methods.

[00:49:08]Okay, there are such concepts.

[00:49:11]Now let's see. Let's short circuit. What is short circuit? Let's go back to the circuit. I am drawing. What have we done here? A resistor is connected.

[00:49:30]Now what do we do? A and B are points.

[00:49:36]What have we done?

[00:49:38]Both points are shorted. Then when we short them, OK, we connect them directly with a solid wire or between the two, then what do we call it? We can call it a short circuit. Okay, so here we can say that the physical connection between A and B is called a short circuit. What can we call it? We can call it a short circuit because we connect it directly or we can draw a little more circuit so that it will be clearer.

[00:50:24]Suppose here we have taken a voltage source. Here I have put a resistance R1. Then here I consider points A and B and put a resistor in parallel with it.

[00:50:37]Now what do we do? If we keep these points A and B open, what will happen if we keep them open? What will happen here? Current will circulate because there is a closed path. Okay, then this circuit will form in this way.

[00:50:53]But what I did here is short it. What I did here is short it. What I did to point A and B is shorted with a solid wire.

[00:51:02]What will happen immediately? This is due to short circuit. What will happen? The circuit will close from here itself. What will happen? The circuit will close from here itself. In this way, a short loop or mesh will form.

[00:51:12]That is, at that place, here. The value of the register becomes zero because we put it in parallel, what do we do in parallel, we do short circuit, we do short circuit in parallel of this register, then short circuit means what resistance will we do, whatever current ok whatever current that current will circulate in such a way that it will go ahead and now it will not be divided, what will it be, where is the short path, first of all we will identify the short path it meets point A to B, then what will it do, it will shift from there completely, now let's see from what source, let's see what is one by R what is e and ba a suppose we now whatever current is that we can call maximum current or infinity current ideally we can call it infinity but practically maximum current which is giving this voltage source or giving current source ok then maximum current will pass through this when what will be the value of this resistance will be zero When will infinity be one by zero, that is, if the resistance value is zero, then what will happen? The current will be infinity or in practical conditions, it will be max. When this resistance is zero, what will be our current? It will be max.

[00:52:32]Then what will happen to this current? It will circulate in such a way and at that time this register will be neglected.

[00:52:40]We will learn this later when we solve numerically. Okay, when our next concept comes, you will get this clear. If you practice this, it will happen.

[00:52:48]Okay, so you will see this, so it is necessary to clear this. Let's see. So what can we call this?

[00:52:55]If this cut is happening, that is, it is being neglected. What can we call this?

[00:53:02]What can we call a redundant branch or redundant register? As we saw in the redundant loop, it is useless but has no use in the circuit or it has no use at all, then what can we call it a redundant branch? We can say then the same here this register is present but is there any current flowing through it or not then we can call that condition what is this redundant register or red branch we can ignore it but clear because it is not in the circuit but it is of no use or it is not used ok sos the open circuit and then the short circuit clear just remember let's revise in simple terms once we short open circuit means what is A and B but there is no physical contact that any element resistor inductor capacitor directly and which one but there is no contact between it directly or any element so what will we call that network open circuit we will call it open network and what will happen here A and B are directly connected are they directly connected now here it is directly connected well why solid a solid wire we are connecting directly we are making direct contact between them not that some element is placed in it If the element is placed, then it is not a short circuit, if it is directly contacting a wire through a solid wire, then what can we call it a short circuit and there is another concept, a closed circuit, generally you do not have it, but you should know the difference between an open circuit, a short circuit and a closed circuit, and along with that, I will give you an example that will make you clear properly. So, what is a closed circuit? What is our closed circuit? You can do it directly in this way or here I will add a register, so what is R1, R2, Rv2 and your voltage source, now what current will flow because the closed current will flow from here. Now why are we calling this a closed circuit or not an open circuit?

[00:55:14]Now you understand that open and short circuit are the main differences. Let me clear you for an example. Suppose we have a road here, okay, that means whatever road there is, what vehicles are running on that road. Vehicles are moving and what were the sidewalks on its side where what do we do, where people walk or we walk?

[00:55:36]Now let's say that where we have been given a way, what has been done, a road has been given, now that road is for walking, that is, what is the sidewalk made for people to walk and what is the road made for cars to walk, then if both are walking in their proper place, then what can we call it, a completely correct position, then if I give it a proper direction or properly, where should it go, that is, whatever current is going from here, look at the current that is going from here, what have I done, provided a path for it, what have I done, provided a path for this current to go and if it is going on the same road, then what is this, a completely current, and what do we call this a closed circuit, what do we call a closed circuit, but suppose it is going on a different road, that is, the road that I have not provided for it, if it is going from that place, then what is the sidewalk? The people above are walking on the road and the cars and vehicles on the road are walking on the pavement.

[00:56:39]What happened is a mismatch. Whatever path we have provided for it, it is following it on another path, that is, it is walking on another path, that is, the cars are walking on the pavement and the people are walking on the road. So what is happening is a mismatch, that is, it is the wrong path. So what can we call it at that place? If we look at this here, I have given it a path. Okay, by giving it a path, what is happening is that it is going on the wrong path.

[00:57:05]That is, will this current go through here? Okay, now that current should have gone through these registers, but what have we done here? We have given it a short circuit. Now this path is not given to it. We are generating this path automatically or short circuiting.

[00:57:21]We hear that a short circuit has occurred at home. So a short circuit has occurred. So what does a short circuit mean? Whatever path is given to the current, it does not follow that path, some unknown path or what can we say? Can which is not used ok if it follows that path what can we call that circuit short circuit ok what is unknown path is this unknown path which we have not provided so what is that path doing it is following the actual path it will go through the register but why is it going there if it had gone from here then what would it be a closed circuit but if it goes from here then what is short circuit ok clear so these open circuits of this type are short circuit and closed circuit then we have to identify them when we are solving the circuit ok if anyone has any doubt till here then ok linear and non linear circuit ok these are also in our circuit but it is a very simple concept one minute so what are linear circuit and non linear circuit now linear circuit what is linear circuit then here we have done a voltage source a register ok now you will not understand this from here where you will understand its characteristics i.e. what is this behavior Okay, now let's see what I'm doing.

[00:59:29]Now what I'm doing here is drawing a graph of the characteristics. Now suppose we have taken the current here and the voltage here. What will happen when we increase the voltage? The voltage increases according to Ohm's law. According to Ohm's law, the voltage increases according to Ohm's law. We will react to this voltage. When I increase this, the current will start flowing through the circuit. And as I increase this, the current will also increase because according to Ohm's law, current is directly proportional to the voltage. In the same way, what is happening is that whatever current we have, its magnitude is also increasing. Okay, so keeping this in mind, what is happening in a linear circuit? Just remember this.

[01:00:38]In a linear circuit, we are increasing the voltage.

[01:00:41]Then what is happening is that the current is also increasing. What is this voltage doing? This current is following this voltage. Okay, its magnitude has increased. What is this voltage doing? Its magnitude is also increasing.

[01:00:56]Or is it directly dependent on this? That is, we meet a straight line. What does a straight line meet?

[01:01:03]Then what does this straight line do? Both of them are now operating at equal levels. So what do we call this a linear circuit? And we have to operate a DC circuit on this linear circuit. That is, a DC circuit is a linear circuit. Okay, a linear circuit is called a linear circuit.

[01:01:21]What is the behavior of both of them? We only decide whether the circuit is a linear circuit or a nonlinear circuit based on how it behaves. So in a linear circuit, we increase the voltage directly, which directly affects the current. It is increasing and it is also increasing in the positive direction. After that, a nonlinear circuit is an element that increases the voltage, but it generates a different characteristic. Let's look at electronics. What is a PN junction diode? What is a semiconductor?

[01:02:14]Now, in semiconductors, you will see that when a semiconductor has a voltage, it has a forward bias voltage.

[01:02:25]When it does this, it cracks.

[01:02:29]Then the current starts flowing through it.

[01:02:30]When it has a forward bias voltage, it cracks. When it is in bias, what will it do? Now, at this temperature, what can we say in general? When the temperature increases, what will happen to the semiconductor? When the temperature increases, when the temperature increases, what will happen to it?

[01:02:48]When its breakdown voltage is reached, what will happen?

[01:02:52]Current will start flowing through it, but what will happen due to voltage? Current flows, leakage current, and due to which the temperature increases. When this temperature increases, the semiconductor will become a conductor, but when the temperature decreases or decreases, then it will become an inductor because it lies between the conductor and the insulator. Then, if the temperature is low, what will happen to the insulator and if the temperature is high, then it will become a conductor. Then, what will we do? Let's take the temperature at one place.

[01:03:33]Okay so temperature and current will be clear to you then suppose what we are doing here is voltage but what we are doing is increasing voltage and or temperature ok that semiconductor itself is increasing voltage and current then when voltage and temperature are increasing up to a particular limit up to a particular limit what will happen from that current will start to circulate i.e. what am I doing increasing but what is happening with current now what is happening is starting to flow what is happening let's wait a minute what we are doing here voltage temperature is increasing ok now what happened here breakdown point has come what happened breakdown point has come then what will happen here this will break here and break means what will this conductor do then at the same time what will happen here we will get a form i.e. what is this linear They are following each other, they are direct straight lines, but what happened in this?

[01:04:38]We only increased the voltage and temperature, and after this breakdown point comes somewhere, it acts in this way, that is, current flows through it or something like that, but you will see the wave form.

[01:04:50]Okay, so what is this, non-linear, that is, they do not follow each other, they are not linear, so what do we call it, non-linear circuit? Okay, so non-linear and linear circuit are clear, let's go to this point. Okay, so this was today's concept, which we covered in the first point, in our first chapter, in the CN and the second, okay, so if you have any doubts in it, you can forget me tomorrow. Okay, and whatever you did not understand, revise it once again, play this video again, okay, but we will meet tomorrow at six. Okay, and if you have any friends, share this video with them. Okay, tell them that our class on ECN is going on every day, Yujas Academy YouTube. If you have a six-day demo on your channel, share it with them too so they can also do these demo lectures.

[01:06:02]Okay, that'll work.