 write down the Faraday's law, Faraday's law of induction. Faraday has conducted a lot of experiment and he found out a law, based on this law only entire chapter is based. Write down the statements Faraday's law of induction, the magnitude of the induced EMF, the magnitude of induced EMF in a circuit. What is a circuit? It is a loop that contains electrical instruments in it, resistance by trains. The magnitude of induced EMF in a circuit is equal to magnitude of induced EMF in a circuit is equal to the rate of change of magnetic flux through the circuit. Rate of change of magnetic flux through the circuit. So what does this law gives you? It gives you what? Magnitude of EMF. Magnitude. It does not tell you which direction the current will flow. It won't. Fine. For that there is separate law. So the magnitude of induced EMF is the rate of change of magnetic flux d phi b by dt. Write this down. This negative sign is coming because of Lenge's law that we will discuss right now. This is the negative sign that signifies that induced EMF will be such, the induced EMF will be such that it will oppose. The induced EMF will be such that it will oppose the cause of creating that EMF. Who is creating EMF? Change in flux. So what it will try to oppose? Change in flux. Change in flux. It will not oppose flux. It will oppose change in flux. And if suppose there are n terms the same formula can become m d phi by dt. Every term there will be a flux associated with it. Now tell me one simple mistake. Suppose you have a loop like this. You have a magnetic field that is coming out. This magnetic field is increasing with time. Which direction the current should flow? Direction of current. Magnetic field is increasing. If flux is changing? So there will be EMF and if there is EMF there will be current. And that current should oppose the cause of it. Now tell me. Every time I ask something this guy is like okay. You don't need that. You just need right end curve rule for everything in magnetism. Everything. So with this work it takes in the opposite direction. Many things will work. But this is like simplest of them. The cause is increase in the flux which direction? This direction. The cause is increase in flux in this direction. So the current should do what? Decrease the flux in this direction. So because of the current, magnetic field should be into the board. Get a hit. So it should be clockwise. Current will be clockwise. Get out. Any doubt? Should we cross it? Now draw another loop. Draw another loop. There is this magnetic field B into the board that is decreasing. Find the direction of current. You can see that easy advance. Not the advance. Tell me which direction the current will be? Clockwise. See what is the cause? Magnetic field decreasing in into the board. So what the induced current will try to do? It will try to increase the magnetic field into the board. It will be clockwise. Now magnetic field is constant. Magnetic field is constant throughout. You have to compress the loop into this shape. Which direction the current will be? Clockwise. But how many? Which direction? Magnetic field is into the board. Going in. See the flux is decreasing in which direction? Into the board. The flux is decreasing because area is decreasing. It will be clockwise. Decreasing into the board. So it will increase into the board. So clockwise. So now I suppose you are experts in finding the direction of current and you can move forward. This one. See what is flux? Flux is magnetic field into area. Area is decreasing. So flux is decreasing. Which flux is decreasing? Into the board the flux is decreasing. So induced current will try to increase the flux because the cause is what? Decrease in flux. Write down a numerical. I am directly taking right now from your NCIT and if you do the homework then we can go to the mains level also because it cannot be done without you practicing the basic level of questions yourself first. Write down a square loop of side 10 centimeter. The square loop of side 10 centimeter has a resistance of 0.5 ohm is placed vertically in east-west plane. Vertically in east-west plane. Magnetic field of 0.1 tesla. Magnetic field of 0.1 tesla is set up across the plane in northeast direction. The magnetic field is decreased to 0 in 0.7 seconds. B1 B2 becomes 0 steadily in 0.7 seconds. Steadily means what? Rate of change of magnetic field is same as average rate of change of magnetic field. Find out the induced EMF and current in the loop. How much is the EMF and how much is the current? Once you get EMF, EMF divided by resistance is the current. Anyone? Draw the diagram properly. Visualize it. 5. 5. Why is it 5? I want EMF and current. Times for 3 or 10 to minus 3? 5. 1 millivolt. All of you getting it? 1 millivolt. Get the current also quickly. What Kevin? Peter-san? I got it. Then you give it to uncle sir. 2 into 10 to minus 3. Fine. Look at here now. This is north direction. This is east. This is of course west and that is south. Where is the top and bottom? Top is this. Bottom is into the board. This is horizontal actually. Like this. So, what was in it? Square loop is placed vertically in east-west plane. Don't talk. East-west plane is a square. Like this. Fine. And magnetic field is in north-east direction. So magnetic field is like this. This is B. The area vector in which direction? This is the area vector of perpendicular to the surface. Getting it? What is the angle B is making with the area vector? 45 degrees. How you find out the area between two vectors? You connect them day to day. The flux is gone. See this entire surface has constant area. Direction is also constant. So the flux is B into A into cos theta. This is case number 2. So the flux is B into area into cos of 45 degrees. B given by B is 0.1. Area is 0.1 into 0.1 meter per convoy. This into 1 by root 2. This is initial flux. Final flux is what? 0. How much time it has taken? 0.7 seconds. Fine. 1 by root 2 is 0.7? 0.7. 0.7. So 1 by root 2 is also 0.7. So in all these things you should remember. You should also remember root 3 by root 2 is what? It actually helps. So 1 by root 2 is also 0.7. So if you find out change in flux. Change in flux is the initial flux itself. Find that initial flux divided by 0.7 is a change in flux. Change in flux divided by time is 0.1 into 0.1 into 0.1 into 1 by root 2 divided by 0.7. So 0.7 and 1 by root 2 gone. So this is 10 square minus 3 volts. And current will be this divided by 0.5.