Now we are going to solve the Thevenin's explanation circuit Let us explain step by step When we apply Thevenin's theorem What parameters should we find out? Vth and Rth How are we going to find out? So explanations Thevenin's explanations We don't need Northons Just use Thevenin's If we ask for Northons This is the answer Take a circuit.
You can ask for any resistance in a circuit. I am taking a very simple circuit without internal resistance. Use it only if given or else I will leave it. So this resistance R1, R2, R3.
Find current through R2. V1, V2. And this is the current.
Find the current through R2 This is the question. A particular resistance wave is asking for current. When it asks like this, how are we going to solve it?
First thing, you have to fix RL. Now, in this circuit, what is RL? R2 What resistance will we find with current? What will be that? R2 So here, first step RL is equal to R2 Since RL is the resistance at which the current is needed.
The current that we are going to find through which the current is needed is called RL. Here we are going to find the current through R2. So RL is equal to R2.
So first step, remove RL. Remove RL. In this circuit, remove RL.
After removing RL, the point that is removed that is the load point is removed. The points connected by RL are A and B. I am taking this as A and B.
You can take it any way you want. R3, V1, V2 So first step, we have decided what is RL. Next step, to determine the Vth.
So we are going to find the Vth. We are going to find two parameters. So first one is Vth.
Finding Vth. Find Vth. To find Vth, first step, remove RL. Remove R I have already given the explanation Vth voltage across the load terminal after removing the load After removing the load, the voltage at the point of removal is there So now the load has been removed this is the voltage of A and B this is the voltage of Vth you can use any method of series parallel Now, if we have a circuit like this, we will find the current that goes through it.
We will take the direction of this current as I. We will take the current I for this circuit. Now, in this circuit, the current that goes through this circuit will go here also. So, what will be the resistance of these two?
It will be series. What will be the resistance applied at one end? V1.
What is applied in this end? V2. So, if we want this current, what is the formula? Let us say it loudly.
V1 minus V2 by R1 plus R3. Right? These two reasons are series. One end is V1 and the other end is V2.
What is this? This is not applied in all of them. You have to use it in every place. It will be like using what we have studied and applying it. We have seen this.
There are two series. So, in this end, V1 is V2. V1 and V2 then the voltage difference is V1-V2 by these two directions series all the circuits are not the same it will change according to the circuit first we have to find the current what we have to find instead of finding the current we have to find the Vth how are we going to find the Vth now the Vth is in two directions we can find the Vth A and B Vth is R1 This is Vth This is one portion So, from A to B, the voltage is Vth The voltage from A to B is Vth Or, we can write A to B can be taken in any direction. This direction can be taken. It can also be taken through R3.
No matter how it is taken, the result will not change. R3 V2 A to B This A to B voltage is called Vth. So, we know the current that goes through this.
I Similarly, the current that comes through this is I. so the current is already found using this formula now I am taking this circuit I need to find Vth in this circuit from A to B so first there is a resistance R1 what current flows after that I, so what drop will be there I into R1 and then I will find R1 we are giving a voltage here, it drops here, the remaining voltage will be available here here there is a voltage, current is coming from that voltage, after the current drops here, the remaining voltage will be available here we will find out what is that voltage so when A to B comes, the voltage has dropped here, I am checking the drop, I into R1 how do I come now? from A to B, I come in this direction Look at my direction.
It is the direction from A to B. It is anti-clockwise. Whereas, the current direction is opposite.
So, what will this change? Minus. Then, where do I cross this battery from?
From plus to minus. This is just like a KVL. That's all.
This is V1. KVL. What is this voltage? So here is a drop minus this voltage If I add both of these I will get this voltage Vth By the way I am going to use this circuit and find out In the exam I am going to use only one No need to use both So which ever circuit I use I am going to find out the direction of the circuit. I am coming from A to B.
When I come here, I need Vth A to B. I cross I into R3. I cross from plus.
Vth is the circuit which is the Vth of this circuit. So, the first step is to find the Vth. Either use this circuit or use this circuit to find the Vth.
So, our formula is IL is equal to Vth by Rth plus RL. So, we have fixed RL and found Vth. What is remaining? Finding RTH How to find RTH We have defined RTH there What we have said Resistance looking from the load terminal after replacing all sources Here they have given two sources in the circuit They have given two sources, they will replace both V1, it does not give interresistance So from here R1 then R2 and V2 will be replaced this point is A and B the load will not come anywhere first step is to remove so removing will bring the rest together so this resistance R1 and this R3 this point value is Rt Rth is the resistance between A to B Now lets find out the Rth What is the connection between these two resistances? See how it is, from A to B How it is a series?
If a current starts from A to B, when it reaches this point, it can flow either this way or this way. How many paths have we seen? Two. What is the connection? This is the mistake everyone makes.
It is a series because they are in the same direction. But what have we done? We have broken in the middle. This is A and this is B. From A to A to B, So, RTH is found.
I can see VTH and RTH. Now, using this, draw the Thevenin's Equivalent Circuits. Next step, draw the Thevenin's Equivalent Circuits. You are drawing the RTH and VTH series that you have found.
Across the load point AB. VTH, RTH. There are two things to be found.
One is Vth and another one is Rth. After finding these two things, we will put the Eclone circuit. So, we will remove the loader. First step is to remove the loader.
We will find Vth. This is the second step. After removing the load, we will find out the resistance inside the point.
We will use both of them to make a circuit. Now connect the load. Connect the load. across AB because load is connected in AB so the disconnected point is AB so load is connected in AB AB So connect the load RL.
This RL is R2. RTH, we know this value. VTH, we know this value. Now the current IL, we know the formula. IL is equal to VTH by RTH plus RL.
Substitute and we get the current. So this is the explanation, if you ask for state and explain, you are explaining with this circuit. Sometimes we ask for 10 marks, when we ask for theoretical question, we say state 1, Thevenin's theorem state 1. So you are giving the explanation, then lastly apply the formula.