[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.37,0:00:01.84,Default,,0000,0000,0000,,- [Instructor] In other\Nvideos, we talk about
Dialogue: 0,0:00:01.84,0:00:04.40,Default,,0000,0000,0000,,how a current flowing through a wire
Dialogue: 0,0:00:04.40,0:00:07.40,Default,,0000,0000,0000,,can induce a magnetic field.
Dialogue: 0,0:00:07.40,0:00:09.25,Default,,0000,0000,0000,,Now what we're going to\Ntalk about in this video
Dialogue: 0,0:00:09.25,0:00:11.04,Default,,0000,0000,0000,,is how we can go the other way.
Dialogue: 0,0:00:11.04,0:00:13.23,Default,,0000,0000,0000,,How a change in a magnetic field
Dialogue: 0,0:00:13.23,0:00:18.06,Default,,0000,0000,0000,,can affect or induce a\Ncurrent in a loop of wire.
Dialogue: 0,0:00:18.06,0:00:20.79,Default,,0000,0000,0000,,We're gonna be going from a change,
Dialogue: 0,0:00:20.79,0:00:25.62,Default,,0000,0000,0000,,change in, and actually we're\Ngonna focus on magnetic flux.
Dialogue: 0,0:00:25.62,0:00:26.45,Default,,0000,0000,0000,,Magnetic.
Dialogue: 0,0:00:27.40,0:00:29.82,Default,,0000,0000,0000,,Magnetic flux through a loop.
Dialogue: 0,0:00:32.04,0:00:33.99,Default,,0000,0000,0000,,Through a loop.
Dialogue: 0,0:00:33.99,0:00:36.10,Default,,0000,0000,0000,,Now we're going to see how this actually
Dialogue: 0,0:00:36.10,0:00:38.89,Default,,0000,0000,0000,,induces a current in that loop.
Dialogue: 0,0:00:38.89,0:00:40.70,Default,,0000,0000,0000,,So, induces.
Dialogue: 0,0:00:40.70,0:00:42.20,Default,,0000,0000,0000,,Induces a current.
Dialogue: 0,0:00:43.04,0:00:44.38,Default,,0000,0000,0000,,Induced current.
Dialogue: 0,0:00:45.77,0:00:46.85,Default,,0000,0000,0000,,This right over here,
Dialogue: 0,0:00:46.85,0:00:49.37,Default,,0000,0000,0000,,all right, this is my attempted\Ndrawing a magnetic field
Dialogue: 0,0:00:49.37,0:00:51.14,Default,,0000,0000,0000,,and these are the magnetic field lines.
Dialogue: 0,0:00:51.14,0:00:52.18,Default,,0000,0000,0000,,They don't look like lines
Dialogue: 0,0:00:52.18,0:00:54.10,Default,,0000,0000,0000,,because they're all\Npopping out of the screen.
Dialogue: 0,0:00:54.10,0:00:56.94,Default,,0000,0000,0000,,They're moving towards\Nyou, towards the viewer
Dialogue: 0,0:00:56.94,0:01:00.52,Default,,0000,0000,0000,,so you could view these\Nas the tips of the arrow.
Dialogue: 0,0:01:00.52,0:01:02.33,Default,,0000,0000,0000,,Now there's different ways\Nof showing magnetic fields.
Dialogue: 0,0:01:02.33,0:01:04.44,Default,,0000,0000,0000,,You could show magnetic\Nfield lines like this,
Dialogue: 0,0:01:04.44,0:01:06.10,Default,,0000,0000,0000,,you could also use vectors.
Dialogue: 0,0:01:06.10,0:01:07.78,Default,,0000,0000,0000,,And when you're using field lines,
Dialogue: 0,0:01:07.78,0:01:09.70,Default,,0000,0000,0000,,it's the density of the field lines
Dialogue: 0,0:01:09.70,0:01:11.91,Default,,0000,0000,0000,,tell you how strong the magnetic field is.
Dialogue: 0,0:01:11.91,0:01:13.23,Default,,0000,0000,0000,,If you got to the right here,
Dialogue: 0,0:01:13.23,0:01:15.25,Default,,0000,0000,0000,,they are less dense and\Nso the magnetic field
Dialogue: 0,0:01:15.25,0:01:18.14,Default,,0000,0000,0000,,is less strong on the\Nright hand side over here
Dialogue: 0,0:01:18.14,0:01:20.34,Default,,0000,0000,0000,,than they are on the left hand side,
Dialogue: 0,0:01:20.34,0:01:23.17,Default,,0000,0000,0000,,or at least that's what\NI'm trying to depict.
Dialogue: 0,0:01:23.17,0:01:24.16,Default,,0000,0000,0000,,Now if we did it with vectors
Dialogue: 0,0:01:24.16,0:01:26.49,Default,,0000,0000,0000,,we would have bigger arrows\Npointing out over here
Dialogue: 0,0:01:26.49,0:01:28.17,Default,,0000,0000,0000,,than we would over here.
Dialogue: 0,0:01:28.17,0:01:30.52,Default,,0000,0000,0000,,But now let's do a loop of,
Dialogue: 0,0:01:30.52,0:01:32.16,Default,,0000,0000,0000,,let's do a loop of wire.
Dialogue: 0,0:01:32.16,0:01:34.64,Default,,0000,0000,0000,,Let me draw a loop of wire here.
Dialogue: 0,0:01:34.64,0:01:38.54,Default,,0000,0000,0000,,Let's say I have a loop of wire that is,
Dialogue: 0,0:01:38.54,0:01:40.54,Default,,0000,0000,0000,,this is my loop of wire.
Dialogue: 0,0:01:41.48,0:01:42.81,Default,,0000,0000,0000,,My loop of wire.
Dialogue: 0,0:01:44.31,0:01:46.27,Default,,0000,0000,0000,,If I just throw that loop of wire
Dialogue: 0,0:01:46.27,0:01:48.60,Default,,0000,0000,0000,,and if it's just stationary,\Nit's in this magnetic field
Dialogue: 0,0:01:48.60,0:01:50.18,Default,,0000,0000,0000,,and the magnetic field isn't changing,
Dialogue: 0,0:01:50.18,0:01:53.43,Default,,0000,0000,0000,,I do have some flux going through the,
Dialogue: 0,0:01:53.43,0:01:55.56,Default,,0000,0000,0000,,I guess you can say the\Nsurface defined by this wire.
Dialogue: 0,0:01:55.56,0:01:57.87,Default,,0000,0000,0000,,And if you're unfamiliar\Nwith the term magnetic flux,
Dialogue: 0,0:01:57.87,0:02:00.72,Default,,0000,0000,0000,,I encourage you to watch\Nthe video on magnetic flux.
Dialogue: 0,0:02:00.72,0:02:02.05,Default,,0000,0000,0000,,But if I just have this wire
Dialogue: 0,0:02:02.05,0:02:03.64,Default,,0000,0000,0000,,stationary in the magnetic field,
Dialogue: 0,0:02:03.64,0:02:05.88,Default,,0000,0000,0000,,nothing is going to happen.
Dialogue: 0,0:02:05.88,0:02:08.49,Default,,0000,0000,0000,,But I will be able to induce a current
Dialogue: 0,0:02:08.49,0:02:11.32,Default,,0000,0000,0000,,if I change the magnetic flux
Dialogue: 0,0:02:11.32,0:02:14.81,Default,,0000,0000,0000,,going through this surface in some way.
Dialogue: 0,0:02:14.81,0:02:16.93,Default,,0000,0000,0000,,So for example, right\Nnow the magnetic field
Dialogue: 0,0:02:16.93,0:02:19.59,Default,,0000,0000,0000,,is pointing out of the screen.
Dialogue: 0,0:02:19.59,0:02:21.51,Default,,0000,0000,0000,,If I were to make it even stronger
Dialogue: 0,0:02:21.51,0:02:25.09,Default,,0000,0000,0000,,in the direction pointing\Nout of the screen.
Dialogue: 0,0:02:25.09,0:02:27.49,Default,,0000,0000,0000,,So, I guess one way to think about it is
Dialogue: 0,0:02:27.49,0:02:30.46,Default,,0000,0000,0000,,if I were to, if the change\Nin the magnetic field,
Dialogue: 0,0:02:30.46,0:02:33.30,Default,,0000,0000,0000,,the change in the flux\Nwere to get even stronger
Dialogue: 0,0:02:33.30,0:02:34.92,Default,,0000,0000,0000,,in the outward direction.
Dialogue: 0,0:02:34.92,0:02:36.26,Default,,0000,0000,0000,,So I don't know, a good way to,
Dialogue: 0,0:02:36.26,0:02:38.57,Default,,0000,0000,0000,,just gonna get even stronger\Nin the outward direction.
Dialogue: 0,0:02:38.57,0:02:40.13,Default,,0000,0000,0000,,I'll draw a big arrow there.
Dialogue: 0,0:02:40.13,0:02:41.08,Default,,0000,0000,0000,,I guess you could say that
Dialogue: 0,0:02:41.08,0:02:45.02,Default,,0000,0000,0000,,these things became even denser\Nin this outward direction.
Dialogue: 0,0:02:45.02,0:02:47.88,Default,,0000,0000,0000,,It is actually going to induce a current.
Dialogue: 0,0:02:47.88,0:02:51.58,Default,,0000,0000,0000,,And the current that it\Nwill induce is going to go,
Dialogue: 0,0:02:51.58,0:02:53.40,Default,,0000,0000,0000,,is going to go in that direction
Dialogue: 0,0:02:53.40,0:02:55.19,Default,,0000,0000,0000,,and let me draw it a little bit clearer.
Dialogue: 0,0:02:55.19,0:02:57.59,Default,,0000,0000,0000,,The current is going to\Ngo in that direction.
Dialogue: 0,0:02:57.59,0:03:01.56,Default,,0000,0000,0000,,It's going to go in a clockwise\Ndirection around this.
Dialogue: 0,0:03:01.56,0:03:04.63,Default,,0000,0000,0000,,And that is because that\Nchange in the magnetic flux
Dialogue: 0,0:03:04.63,0:03:06.66,Default,,0000,0000,0000,,that induces a voltage,
Dialogue: 0,0:03:06.66,0:03:11.02,Default,,0000,0000,0000,,an electromotive force that\Ncauses this current to flow.
Dialogue: 0,0:03:11.02,0:03:13.04,Default,,0000,0000,0000,,That causes the current to flow
Dialogue: 0,0:03:13.04,0:03:15.29,Default,,0000,0000,0000,,and there's other ways to\Nchange the magnetic flux.
Dialogue: 0,0:03:15.29,0:03:18.46,Default,,0000,0000,0000,,If I were to lessen the magnetic field
Dialogue: 0,0:03:19.43,0:03:21.01,Default,,0000,0000,0000,,in the outward direction or another way,
Dialogue: 0,0:03:21.01,0:03:23.74,Default,,0000,0000,0000,,if the change in the\Nmagnetic field were inwards,
Dialogue: 0,0:03:23.74,0:03:25.70,Default,,0000,0000,0000,,then the current would\Ngo the other direction.
Dialogue: 0,0:03:25.70,0:03:28.28,Default,,0000,0000,0000,,But the key here is when I change the flux
Dialogue: 0,0:03:28.28,0:03:32.36,Default,,0000,0000,0000,,through this surface defined by this wire,
Dialogue: 0,0:03:32.36,0:03:34.30,Default,,0000,0000,0000,,it's going to induce a current.
Dialogue: 0,0:03:34.30,0:03:36.32,Default,,0000,0000,0000,,The current isn't going to\Nbe there if the thing is,
Dialogue: 0,0:03:36.32,0:03:37.90,Default,,0000,0000,0000,,if the magnetic field is stationary
Dialogue: 0,0:03:37.90,0:03:41.24,Default,,0000,0000,0000,,and I'm not changing this loop in any way.
Dialogue: 0,0:03:41.24,0:03:43.73,Default,,0000,0000,0000,,But as soon as I change\Nthe flux in some way,
Dialogue: 0,0:03:43.73,0:03:45.66,Default,,0000,0000,0000,,I am going to induce a current.
Dialogue: 0,0:03:45.66,0:03:48.22,Default,,0000,0000,0000,,I could also instead\Nof changing the field,
Dialogue: 0,0:03:48.22,0:03:50.72,Default,,0000,0000,0000,,I could actually move my coil.
Dialogue: 0,0:03:52.82,0:03:54.10,Default,,0000,0000,0000,,I could move it that way.
Dialogue: 0,0:03:54.10,0:03:55.29,Default,,0000,0000,0000,,And if I were to move it that way,
Dialogue: 0,0:03:55.29,0:03:58.81,Default,,0000,0000,0000,,the flux going through this surface
Dialogue: 0,0:03:58.81,0:04:01.62,Default,,0000,0000,0000,,or I guess coming out of\Nthis surface will increase.
Dialogue: 0,0:04:01.62,0:04:03.14,Default,,0000,0000,0000,,Because if I move this to the left,
Dialogue: 0,0:04:03.14,0:04:05.41,Default,,0000,0000,0000,,the magnetic field is denser,
Dialogue: 0,0:04:05.41,0:04:07.77,Default,,0000,0000,0000,,I guess it's stronger\Nso there'll be more flux
Dialogue: 0,0:04:07.77,0:04:08.96,Default,,0000,0000,0000,,through this area here.
Dialogue: 0,0:04:08.96,0:04:10.30,Default,,0000,0000,0000,,So, if you move it that way,
Dialogue: 0,0:04:10.30,0:04:12.10,Default,,0000,0000,0000,,you also would have a current like this.
Dialogue: 0,0:04:12.10,0:04:13.63,Default,,0000,0000,0000,,Now if you moved it the other way,
Dialogue: 0,0:04:13.63,0:04:16.19,Default,,0000,0000,0000,,if it was on the left hand\Nside and you moved it that way,
Dialogue: 0,0:04:16.19,0:04:17.81,Default,,0000,0000,0000,,it would also induce a current
Dialogue: 0,0:04:17.81,0:04:19.66,Default,,0000,0000,0000,,but now since the flux is lessening
Dialogue: 0,0:04:19.66,0:04:20.83,Default,,0000,0000,0000,,in the outward direction,
Dialogue: 0,0:04:20.83,0:04:23.13,Default,,0000,0000,0000,,the current would go in the other way.
Dialogue: 0,0:04:23.13,0:04:24.54,Default,,0000,0000,0000,,Now there's other ways to change the flux.
Dialogue: 0,0:04:24.54,0:04:28.18,Default,,0000,0000,0000,,You could actually change\Nthe area of this actual loop
Dialogue: 0,0:04:28.18,0:04:29.63,Default,,0000,0000,0000,,if somehow it was made out of some
Dialogue: 0,0:04:29.63,0:04:33.43,Default,,0000,0000,0000,,maybe stretchy, stretchy wire somehow.
Dialogue: 0,0:04:33.43,0:04:35.97,Default,,0000,0000,0000,,If you increased its,
Dialogue: 0,0:04:35.97,0:04:37.50,Default,,0000,0000,0000,,if you would increase.
Dialogue: 0,0:04:37.50,0:04:39.59,Default,,0000,0000,0000,,Let me draw it this way.
Dialogue: 0,0:04:39.59,0:04:42.84,Default,,0000,0000,0000,,If you were somehow able to stretch it.
Dialogue: 0,0:04:44.28,0:04:47.03,Default,,0000,0000,0000,,Stretch it so it contains,
Dialogue: 0,0:04:47.03,0:04:50.21,Default,,0000,0000,0000,,so the actual area increases.
Dialogue: 0,0:04:50.21,0:04:51.67,Default,,0000,0000,0000,,If you were able to stretch it out
Dialogue: 0,0:04:51.67,0:04:53.19,Default,,0000,0000,0000,,so that the actual area increases
Dialogue: 0,0:04:53.19,0:04:55.05,Default,,0000,0000,0000,,which would cause the flux in the
Dialogue: 0,0:04:55.05,0:04:57.60,Default,,0000,0000,0000,,out of the screen direction\Nto increase even more,
Dialogue: 0,0:04:57.60,0:04:59.75,Default,,0000,0000,0000,,that also would induce,
Dialogue: 0,0:04:59.75,0:05:02.12,Default,,0000,0000,0000,,that also would induce the current.
Dialogue: 0,0:05:02.12,0:05:06.50,Default,,0000,0000,0000,,And so this whole idea of\Na change in magnetic flux
Dialogue: 0,0:05:06.50,0:05:09.38,Default,,0000,0000,0000,,inducing a current, this is the essence
Dialogue: 0,0:05:09.38,0:05:11.64,Default,,0000,0000,0000,,and we'll go deeper into\Nit in future videos,
Dialogue: 0,0:05:11.64,0:05:14.72,Default,,0000,0000,0000,,this is the essence of Faraday's Law.
Dialogue: 0,0:05:15.65,0:05:16.48,Default,,0000,0000,0000,,Faraday's,
Dialogue: 0,0:05:18.05,0:05:19.22,Default,,0000,0000,0000,,Faraday's Law.
Dialogue: 0,0:05:21.28,0:05:23.67,Default,,0000,0000,0000,,And we'll quantify this\Nmore in future videos
Dialogue: 0,0:05:23.67,0:05:27.64,Default,,0000,0000,0000,,but it's just the notion\Nthat if I have a loop of wire
Dialogue: 0,0:05:27.64,0:05:29.78,Default,,0000,0000,0000,,and I have a changing magnetic flux
Dialogue: 0,0:05:29.78,0:05:31.42,Default,,0000,0000,0000,,through the loop of wire,
Dialogue: 0,0:05:31.42,0:05:35.34,Default,,0000,0000,0000,,that is going to induce\Na current in that wire.