 Okay guys, I'll wait for 5 minutes before I start the class because only 5 people have joined Please type the topics that you want me to cover in this class Okay guys, I'll wait for 5 minutes before I start the class Okay, which topic should I cover today? Any particular topic or any particular doubt that you guys have? Okay, motors and generators Okay, motors Okay, only 3 people here 2 more minutes I'll start from 3.30 Let me wait, people perhaps may join later Okay, so I'll start doing motors now I'll just download the NCERT content and I'll upload it Okay, guys, let's start So if people are not joining, I cannot do anything Okay, so electric motor and electric generator is a concept which is best on magnetic effects of current So current carrying conductor has so many applications in electrical world And electric motor and generator are an application of that Now let me go to motor first Before that, I need to teach you few things Okay, so before that I need to teach you electromagnetic induction And what is electromagnetic induction? So there are two things So suppose I have a current carrying conductor here And there is no current flowing through it The current is not live Sorry, the conductor is not live and there is no current flowing through it Now there was a scientist known as Faraday Faraday did a lot of experimentation During his experimentation, he found one particular phenomenon What was that phenomenon? So a non-current carrying conductor was kept in the vicinity of Suppose a magnetic pole over here Now what happened? Whenever the distance between the magnetic pole and the current and the conductor is changing Or suppose frequently or I am changing the distance between the magnetic pole and this conductor What was observed that if it is changing continuously If the distance between the magnetic pole and the conductor is changing continuously A current is observed in this conductor It means that if I am changing the distance between this magnetic pole and this wire What am I doing? I am actually changing the magnitude of the magnetic field If I bring this pole nearer to this wire The magnitude of the magnetic field will increase If I take it away from the wire The magnitude of the magnetic field will change Or it will reduce So what happens? Changing magnetic field Presence of changing magnetic field in the vicinity of this wire Creates or it leads to flow of a current in this particular wire So what I am trying to say is that Due to change in the either magnitude of the or the direction of the magnetic field If a conductor is kept near to that where the magnetic field is changing You will observe a current in that conductor But how does that current gets I mean how does that current get evolved The current gets evolved by a process known as electromagnetic induction So you try to understand magnetic field is Antiproportional to 1 by r square and proportional to I So or I or in this case in permanent magnet The polar strength So whatever mm you can say So it is proportional to m and it is antiproportional to 1 by r square So what happens if I have a fixed magnet The m does not vary What I do is that if I change this distance magnetic field over here will change And due to change in magnetic field what will happen Across the two sides of this wire EMF would be generated What is EMF? EMF will form is electromotive force And this is nothing but voltage So a voltage difference between created between the two sides of the wire And due to this voltage difference as resistance is already existing in this wire V is equal to IR So a voltage difference is getting created And I would be equal to V divided by R And this particular phenomenon of creation of or Evolvement of electric current inside a conductor Due to changing magnetic field is known as electromagnetic induction So creation of EMF due to changing magnetic field is known as electromagnetic induction Then there was another scientist His name was Lynch and what he did He told that actually he was trying to prove Newton's third law and inertia Basically both So what he told that in which direction the current should develop So the thing is that you have already studied that whenever a current carrying conductor is there It creates a magnetic field around it So whenever in this scenario also as soon as the current starts flowing Or the current generates over here in this case This particular current will start producing its own magnetic field And already I have a magnet here which has its own magnetic field It means that after creation of current in the conductor There are two kinds of magnetic field interacting with each other One magnetic field created due to magnetic pole which was present while I was doing the experimentation And the second magnetic field would be the field created due to creation of current in the conductor Now in which direction the current will flow So always remember that the current would be generated in a conductor in such a way That it opposes the change in the magnetic field due to which this is getting created I am again saying it Any particular object will always resist change in it What is the change? Change is development of EMF across its two sides And due to development of EMF a current flows But the nature of the current would be such that it will start opposing the magnetic field Due to which this current is getting created It means that the magnetic field of the pole and the magnetic field created by the current carrying conductor Would always be in opposite direction So direction of the current would be in such that the magnetic field created by it Is in opposite direction of the magnetic field created due to pole That's what we have to understand And this is what Lenge's law is So after I teach you Lenge's law and all these things So there is one thing which is With which you can find out the direction of the magnetic field here And that is our direction of the current here that is Fleming's left hand rule Sorry right hand rule So there are your index finger would be direction of magnetic field Your middle finger would be direction of current And your thumb would be direction of motion Which is nothing but direction of force also So that is what the concept is Now what is the concept of generator So I have an alternating current generator Or it is also called dynamo So alternating current generator is also called dynamo So what is the concept So if you have your book just go through the construction and all What happens is that I will explain you in very layman term So I have current carrying conductor And in what type I have current carrying conductor Because I have to I mean if it is a generator AC generator means what? Input is AC or output is AC As the name suggests AC generator means AC current generator That means that output current after creation of electricity would be AC current Would be an AC current So AC generators always produces AC current Is it okay? And then there comes how do you construct it So here I have magnetic pole And how do I create magnetic pole? So on two sides of the conductor The current carrying coil would be rounded on a core Is it okay? And that core would be fixed between It will not be fixed The core would be free to rotate between To fix magnetic pole So try to understand Here is my magnetic pole This is magnetic pole Suppose this is north pole and south pole And here with a shaft I have cylindrical core And on this core current carrying conductors has been Coiled like this So this is a current carrying conductor And now what happens? This particular core Where the current carrying conductors are rounded up Is combined with a rotator So what happens? Why it is combined with a rotator? So try to understand my objective would be I know that by Faraday's law If there would be a changing magnetic field In this current carrying conductor Current would be generated And I can utilize that current as output So what I do? These poles are fixed So I cannot rotate pole What can I rotate? I can rotate this particular core Which contains iron Just give me a moment guys So what will happen is I cannot rotate this permanent magnet They are very heavy and rotating It is very difficult What I can rotate is this core On which this coil has been wrapped up So how do you rotate this coil? The coil is joined with a rotator Is it okay? This rotator is rotated With the help of so many things One being steam So rotator you have fans On the fans the steam comes And strikes the fan Due to the energy that the steam carries with itself When it strikes with the fan of this rotator The fan starts moving As soon as the fan starts moving This is coupled with this core The core starts moving As soon as the core starts moving What happens is The direction of the magnetic field At each point will keep on changing As soon as the direction of the magnetic field And the magnitude of the magnetic field changes What happens over here is That there is a change in flux Now I forgot to define flux What is flux? Flux is number of magnetic field lines Cutting any particular area Any particular unit area Number of magnetic field lines Cutting per unit area Or number of magnetic field lines Passing through per unit area Is also known as flux So what happens is As soon as they start This will start rotating The flux will change Due to change in flux What will happen? Suppose this is one end of the conductor Or wire And this is the second end of the wire So what will happen? The current will be generated here The current would be an AC current generated And this current would be taken outside somewhere here And this will be passed on So AC current is nothing but AC generator is nothing but An example of electromagnetic induction How do we apply electromagnetic induction here? So we know that changing or varying magnetic field Will be able to create EMF Around the two sides of the coil So here what I am doing Instead of changing the magnitude I am rotating it So that primarily the direction At each point of the conductor changes At the direction of the magnetic field Created by the poles Is changing on each point of the conductor Due to change in flux EMF would be generated Due to that EMF The current would be generated in the circuit And that current would be received outside And would be utilized for different purposes So that is how it is So did you understand electric generator guys? Just forced yes or no? Did you understand electric generator? Tell me otherwise I will repeat once again Param did you understand? Okay now let me move to motors What is a motor? So generator is conversion of mechanical energy Into electric energy Motor is exactly different Motor is conversion of electrical energy Into mechanical energy So it means that Okay here where is split and split rings Can we just Okay fine In motors right here the split rings and all Here in motors you are asking In generators because I don't have figure Which book you are referring I cannot understand So I have the NCRT book Where in electrical motors Or in motors split rings and all are used Okay I will explain once you let me know I will explain Okay so what happens is Once again let me draw a figure Okay so what I am doing is I will upload a few pictures here Okay so look at this image What is happening here I will upload one more image So see what is happening There are two images which I have uploaded On the screen One which looks like a motor And one which is an experimentation So rings and brushes are like this Which are nothing but Which will provide support to the coil And which will control or Which will receive or either send The current to this coil If current is coming out It will help in receiving the current And it will maintain the contact properly And also if the current is going inside Again it will maintain the contact easy Or in a very smooth manner And let the current pass in the conductor So that is the use of it Now how does motor works What is the principle of motor working So there would always be a source battery Or a source of power I already told that I already told that a motor is A device which converts Electric energy into mechanical energy It means that motor input Would be electric energy So from where does electric energy comes Electric energy Passive electric energy would come from any battery Like here I am using passive electric energy In the form of battery Or in case of active electric energy I can join the two sides of the coil With some AC or DC current Which is available So like in home If I want to conduct Connect motor Like we have motors in For our water purposes and also They are AC motors Which are working over there So what I do is that I take input from any of the circuit Present in my house And I connect the two ends of the coil Which is present inside the motor To that AC input And due to that AC input The motor starts rotating How does it rotate I will explain you now Now what happens So if it is connected To any particular energy source In this case battery So what happens When circuit gets completed A current will start flowing Flowing through this conductor So you can see Suppose I name it A, B, C, D So A, B, C, D So current is flowing from A to B B to C, C to D Unlikewise So what happens is What happens is Because there is a current carrying conductor And this is See what has been kept over here This is nothing but your magnet So what is happening I am giving it a particular Try to understand guys I am giving it electrical energy So current would be I over here And an external magnetic field is present Due to this particular magnetic pole So what happens See we all know that whenever A current carrying conductor Is placed inside an external force A force would be A conductor Here some amount of force would be applied On different arms of this conductor And because A force is getting applied So see here Direction of the force has been made Direction of the force is this side On this particular coil Direction of the force is on this side So what will happen Due to force being applied on these coils These coils will feel some amount of momentum Some amount of torque Due to that torque This will start rotating As soon as it will start rotating A shaft would be So look at here This starts rotating So when it starts Stator means So look at here There are two parts Stator and commuter So what happens What is commuter Stator is this part Which is creating your magnetic field And here I have given input And as soon as current starts flowing Due to force applied On the current carrying conductor This will start moving And this moving part is known as commuter So this is what the principle of electric motor is Any doubt guys Tell me Any doubt Ask questions Okay Fine Any other doubt that you have Param you have any other doubt People ask me motor and generator I have already explained it If there is any other doubt Guys let me know In any particular topic Should not be related only to Magnetism or electricity or optics Any topic that you have doubt Ask me I will revise it I will not waste your time I know you have other exam So whatever doubt you have I will clarify it And wrap up the session Yes Param asked me a great question Why it is easier to transmit AC current So try to understand Param Whether it is AC current or DC current It depends on the amount of current Which is getting transmitted So suppose So what happens in this case is That first thing is magnitude of the current So suppose what happens Like I was working in a power plant And that power plant used to generate 165 megawatt of electricity So Voltage would be Whatever is voltage I mean Vi cos theta Is total 165 megawatt So suppose current produced is Some 50 Mbps for that matter For your understanding I am saying 50 Mbps or maybe 100 Mbps Or 2000 Mbps or likewise Now try to understand If it is DC current and if it is AC current How does it differentiate from each other So suppose I have two power stations Near to each other One is producing 2000 Mbps DC current And one is producing 2000 Mbps AC current Now I know that the power losses Due to transmission of electricity Is I square R Which means that If I am using same material For transmission for both DC current And both DC and AC current Then I am removing The R value also The power loss I square R Would be directly proportional To the current flowing over here So if both the currents are 2000 Mbps Then the power loss in both the circuits Or both the transmission lines would be same But what happens Generally in AC current We don't let the current to be too high How do we reduce The amount of current to be transmitted We use a transformer Now what is transformer? Transformer is a device Which has an input and output And a core inside It works in such a way that The power transmission remains same On both the sides It means that whatever power it receives From input side The same power it delivers from output Sides hence power loss Is almost zero Now you can say that How it is possible So try to understand that Suppose This is the primary side Of the transformer And this is the secondary side Of the transformer So this is like this And Primary side is taking voltage V1 And suppose current here Is I1 So Secondary side here Is voltage V2 And current is I2 Suppose number of tons in the coil Is N1 here and number of tons In the coil is N2 here So I1 by N1 Is equal to I2 by N2 So I2 Is N2 by N1 I1 So it only depends on How many coils How many tons in the coil one side has So suppose if secondary side Has more number of coils If N2 greater than N1 Then I2 would also be Greater than I1 So what happens I have more current here Now in opposite case If N1 is greater than N2 Then I1 will be greater than I2 So what I do is that The transformer is a device and the relationship Is power is same So V1 I1 is equal to V2 I2 So what happens when I have More number of tons here And less number of tons here So the current generated in this particular circuit Would be lesser Than the current in primary circuit Hence stepping down Of the current is easier for AC current DC current cannot be stepped down DC current cannot be stepped up Suppose you are producing 2000 mps You will have to transmit 2000 mps Hence your power losses would be too much If you are producing 2000 mps AC current In that particular scenario Stepping down this current And bringing down your power losses Would be much easier with the help of transformer That is why in power Transmission AC current is used Any other doubt Ask guys what are you guys Doing you have no doubt in physics I can start asking different question And then you will say this is the doubt That is the doubt Param did you understand Yes, energy is conserved So what happens Param is When Suppose V1 is 200 and I1 is 10 So power on this side is 2000 So if I make current 5 here this will automatically Become 400 So what happens is Energy is conserved on both the sides So if 2000 It is here it will be 2000 on the other side If current is reducing here Voltage will increase If voltage is less here Voltage would be more and if current is more here Current would be less here So that is how Yes the voltage will increase on the other side So this This will be the condition V1 I1 is equal to V2 I2 So if there is a reduction In current the voltage will increase So we always transmit the power At more voltage and less current Why less current because I want I2R losses to be less And hence we reduce the current Any other doubt guys Please ask me there is no point Doing something new in this class Ask the other doubts Because I can take any topic start teaching you And you will feel bored If you don't have doubt over there Post your doubts Otherwise Do and study If you don't have any doubt What do I need to do next Okay Let me give you a question So write down a question I am just orating it Write down the question The question is Find the magnetic Field Find the magnetic field At a distance of 10 cm From a Long straight conductor Carrying a current of 10 ampere A long Straight current carrying conductor is there Which is carrying a 10 ampere current in it You have to find out Magnitude and the direction of Magnetic field 10 cm east of the magnetic field Of the magnetic current Of the current carrying conductor What's the answer Question is there is a long Straight current carrying conductor It carries a current Of 10 ampere You have to find out magnetic Field at a distance of 10 cm And direction also The point At which you have to find out the magnetic field Is 10 cm East of the current carrying conductor Did you find the answer No it's not 2 x 10 to the power minus 7 No it's not 2 x 10 to the power minus 7 But perhaps you have not Converted centimeter into meter Param just converts centimeter into meter Param just converts centimeter into meter Did you get the answer Param It will be 2 x 10 to the power minus 5 No minus 5 Param just do it See The formula is You got it For others the formula is B is equal to mu naught by 2 pi I by D So I would be How much I would be 2 x 10 to the power minus 7 Sorry mu naught by 2 is 2 x 10 to the power minus 7 I is 10 amperes And D is 10 x 10 to the power Minus 2 So this 10 10 gone This 10 to the power minus 2 will go above And it will become 10 to the power plus 2 So this will be nothing but 2 x 10 to the power minus 5 Which is nothing but 20 x 10 to the power minus 6 So which is nothing but 20 mu t That is the answer Second question Second question is I am I am orating the question Find the ratio of magnetic field At a distance 5 centimeter From a long Straight current carrying conductor So there is a long Straight current carrying conductor And you have to find the ratio of magnetic fields At 5 centimeter From it and 50 centimeter From it So suppose 5 centimeter from it The magnetic field is B1 50 centimeter The magnetic field is B2 You have to find B1 is 2 B2 What's the answer This is the easy question Tell me the answers The question is There is a long straight current carrying conductor And there are two points One is 5 centimeter and second One is 50 centimeter apart from it The magnetic field At 5 centimeter point is B1 At 50 centimeter point is B2 You have to find out B1 is to B2 One answer which I am getting Is 10 is to 1 There is a second answer Anyone who is getting the answer 10 is to 1 is the right answer So you look at here Only B is antiproportional to D So B is antiproportional to D It means that B1 Or BD is equal to constant So B1 B1 is equal to B2 D2 So B1 by B2 Is equal to D2 by D1 D2 is equal to 50 D1 is 5 inch so this is 10 So 10 is to 1 is the racing As simple as that Okay So any other doubt that you have guys I have solved two questions If you have any other doubt Ask me otherwise I will wrap up the session now Any particular doubt in optics Let me ask section wise Any particular doubt in optics Electricity Just post it in the chat box Okay Anyone else do you have any doubt I will wait for one minute Otherwise I will wrap up the session Okay Nobody is speaking So I will wrap up the session