 If we move a coil in a region of magnetic field, let's say, towards or away from this magnet, just like this, we can see the bulb glow. So that means there is some induced current in this coil and that means there is some induced EMF. Now if there is induced current in the coil, that means the electrons are moving. And it is the Lorentz force, it is the Lorentz force which is given by Qv cross B, which provides the force for the electrons to move. But what about the case when we move the magnet towards and away from the coil? Even in this case, we can see the bulb glowing. That means there is some induced EMF and that means there is some induced current as well. But who is pushing these electrons to create this current? We know that the coil was stationary, so electrons did not have any velocity to begin with. This V right here was zero. So who pushed these electrons in the first place? That is what we will explore in this video. Let's say we have a region of magnetic field and there is a coil kept inside of it. Now let's say that the strength of the magnetic field is increasing at a constant rate. So that means that the flux through the loop through this coil must be constantly increasing. And we know that there will be some induced EMF and current in this coil. And we can think about the direction of the current using Lenz's law. If the field is increasing in the direction away from us, so a magnetic field must be generated to oppose that. So that should point towards us. And using the right hand curl rule, if we point our thermally direction of the generated magnetic field that is upwards, the curl of our fingers gives the direction of the current. And we can see that will be anticlockwise in this case. So there will be a current in the anticlockwise direction in this coil. Now why does this current flow? Why do the electrons start to move in the first place? There has to be a reason for the electrons to move. It's not the Lorentz force V cross B because the coil is stationary. So magnetic field isn't making them move. In fact, they are being induced to move by the changing magnetic field. So if magnetic field isn't making them move, then it must be an electric field and that's what it is. It must be that an electric field is induced in this loop. So if we look inside this thing and draw a bunch of electrons, there's no way that they are going to move unless there is an electric field. That's the only thing that can push them. If it's not the magnetic field, then there has to be an electric field to push them. So there is an electric field circulation around the loop and the direction of the electric field is in the same direction as that of the current. Because if the current is in an anticlockwise direction, that means the electrons are moving clockwise because the force on the electron, the force on the electron will always be in the direction, it will always be in the direction opposite to that of electric field. And we know that induction occurs all the way around the loop. So the electric field is all the way around the loop. So here's the big idea. A changing magnetic field induces changing electric fields. The electric field that you see over here, it's not stuck in space. They constantly disappear and reappear. So that's why we say changing electric fields. Now here's a strange part. These electric fields are induced even when there is no coil that deserves two exclamation marks. Now we are saying that whether there is a coil or not, if we make the coil disappear, there will be an induced electric field. Because the induced electric field does not require electrons to be there. It is induced as a result of changing magnetic field. An electric field can be induced in a space or vacuum. And these form throughout the space concentric to each other. So there is a smaller one here and there will also be a bigger one right here. Now if this is how induction really works, then we need to rewrite Faraday's law and include this induced electric field that we just saw. So we know that EMF is worked on per unit charge. That is W divided by Q. And if there is an electron moving through the loop, then there will be some work done on it. The force that will do the work is provided by the electric field. And that is given by the charge on the electron, that is small e multiplied by the magnitude of the induced electric field. Now we can write work as integral of f dot dl. And over here, f is charged on the electron multiplied by the magnitude of the induced electric field. So we can place that over here and when we do that, we will get this is equal to the charge on the electron integral of e dot dl. Now if we divide both the sides by the charge on the electron to get the EMF, we will get W divided by e equal to integral of e dot dl. And work done per unit charge is the EMF. So this becomes equal to the EMF. And previously we have seen that EMF is equal to the rate of change of magnetic flux. So we can rewrite Faraday's law. Let me just make some space over here. We can rewrite it in this manner. EMF is equal to integral of e dot dl. And that is equal to the rate of change of magnetic flux. Now because we are integrating over a closed loop, we add a closed loop integral over here. And this is the integral form of Faraday's law. Alright, so we started with how moving magnets make the bulb glow. And finally we are ending with changing magnetic fields, induced looping and circular concentric electric fields. And we expressed what we learned mathematically and included the factor of induced electric field into a Faraday's law. And now a Faraday's law is complete. It's nice to see how far we have come.