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Current time:0:00Total duration:5:37

Video transcript

in other videos we talked about how a current flowing through a wire can induce a magnetic field and we're going to talk about in this video is how we can go the other way how a change in a magnetic field can affect or induce a current in a loop of wire so we're going to be going from a change change in and actually we're going to focus on magnetic flux magnetic magnetic flux through a loop through through a loop and we're going to see how this actually induces a current in that loop so it induces induces a current induced current so this right over here I this is my attempt at drawing a magnetic field these are the magnetic field lines they don't look like lines because they're all popping out of the screen they're moving towards you towards the viewer so you could view these as the tips of the arrow and there's different ways of showing magnetic fields you could show magnetic field lines like this you could also use vectors and when you're using field lines it's the density of the field lines tell you how strong the magnetic field is so if you go to the right here they're less dense so the magnetic field is less strong on the right-hand side over here then they are on the left-hand side or at least that's what I'm trying to depict now if we digit with vectors we would have bigger arrows pointing out over here than we would over there but now let's do a a loop of let's do a loop of wire let me draw a loop of wire here so let's say I have a loop of wire that is so this is my loop of wire my loop of wire so if I just throw that loop of wire and if it's just stationary and it's in this magnetic field and the magnetic field isn't changing I do have some flux going through the I guess you say the surface defined by this wire and if you're unfamiliar with the term magnetic flux I encourage you to watch the video on magnetic flux but if I just have this wire stationary in the magnetic field nothing is going to happen but I will be able to induce a current if I change the magnetic flux going through this surface in some way so for example right now the magnetic field is pointing out of the screen if I were to make it even stronger in the direction pointing out of the screen so I guess one way to think about it is if I were to if the change in the magnetic field the change in the flux were to get even stronger in the outward direction so I don't know a good way to so it's going to get even stronger in the outer direction I'll draw a big error there I guess you could say that these these things became even denser in this outward direction it is actually going to induce a current and the current that it will induce is going to go is going to go in that direction and let me draw a little bit clearer the current is going to go in that direction it's going to go in a clockwise direction around this and that is because that change in the magnetic flux that induces a voltage an electromotive force that causes this current to flow that causes the current to flow and there's other ways to change the magnetic flux if I were to if I were to lessen the magnetic field in the outward direction or another way if the change in the magnetic field were inwards then the current would go the other direction but the key here is when I change the flux through this through this surface defined by this wire it's going to induce a current the current isn't going to be there if the thing is if the magnetic field is stationary and I'm not changing this this this loop in any way but as soon as I change the flux in some way I am going to induce a current I could also instead of changing the field I could actually move my I could actually move my coil I could move it that way and if I were to move it that way the flux going through this surface or rag is coming out of this surface will increase because if I move this to the left the magnetic field is denser I guess it's stronger so there'll be more flux through this area here so if you move it that way you also would have a current like this now if you moved it the other way if it was on the left hand side and you moved it that way it would also induce a current but now since the flux is lessening in the outward direction the current would go in the other way now there's other ways to change the flux you could actually change the area of this actual loop if somehow it was made out of some maybe stretchy stretchy wire somehow if you if you increased its if you had increased let me draw it this way if you are somehow able to stretch it stretch it so it contains so the SIRT the actual area increases if you're able to stretch it out so that the actual area increases which would cause the flux in the out of the screen direction to increase even more that also would induce that also would induce the current and so this whole idea of a change in magnetic flux inducing a current this is the essence and we'll go deeper into it in future videos this is the essence of Faraday's law Faraday's Faraday's Faraday's law and will quantify this more in future videos but it's just the notion that if I have a loop of wire and I have a changing magnetic flux through the loop of wire that is going to induce a current in that wire