 Hi, I'm Zor. Welcome to a new Zor education. Previous lecture was basically introductory to magnetic fields and certain causes that might actually be the reason for magnetic properties. I will probably repeat the most important part today. Today I would like actually to get inside the permanent magnet and try to reason why it behaves like it behaves. It's a model. Again, everything is a model. However, it kind of corresponds to whatever people observe in their experiments with the real magnets. Now this lecture is part of the course Physics for Teens. It's presented on Unisor.com. Now the website Unisor.com is an educational website where all these lectures are combined into courses. There is a Maths for Teens course and there is a Physics for Teens course and some others. And I do recommend you to watch this lecture from the website because it references the real location on YouTube. But if you found it on YouTube, you don't have anything but the lecture. The website contains the whole course and every lecture has very detailed notes. There are exams, etc. And the site is completely free, no advertising, no financial strings attached. So you can just freely get into it. You don't even have to sign in. I mean, if you do, that gives you a little bit more advantages and functionality. Okay, so let's get back to our magnets and try to look inside what's happening. Now in the previous lecture I was talking about electrons and their movement being the main reason for magnetism. So we were considering an electron which is on orbit around the nucleus. So there is an axis around which the electron is rotating and there is a plane of rotation. And we were talking about two electrons are rotating on the same axis on parallel planes and if their location is in the same direction, they're kind of helping each other. And there is something, which we don't know why, but there is something which this model assumes exists some kind of attraction between them. If however, so that's this particular model, if however, rotation of the electrons is in opposite direction, they kind of disturb each other and they're trying to move apart. It's kind of natural if you are in a crowd, let's say in the crowd is moving to the same direction. It's easier obviously and if you have some people moving in one direction and just in front of them are other people who are moving in opposite direction, it's difficult, I mean they disturb each other, they prevent each other from free movement. So that's kind of a model, again it's a model, it's explanation which is in people's mind. I don't know what exactly is happening. I don't think anybody knows what exactly is happening, but it's a good model. So this is when they disturb each other and they're trying to move apart, this is when they are helping each other and they're trying to move closer to each other. And that's this trying, trying means there is some kind of a force and that's the magnetic field is, what is magnetic, what is the field? Field is a force field, right? So that's why we have this kind of a magnetic effect. That was kind of a main idea from the previous lecture and I repeated for the purpose of explaining how things really happening in the permanent magnet. So let's start with permanent magnets. Now, let's just consider two different views. One view is, I would say it's axial view, it's view along the axis of rotation. Now, permanent magnets are permanent because all their electrons, well probably almost all, all of these electrons inside the permanent magnet, they are aligned, which means their axis of rotation are parallel to each other. So this is the model of their axis are parallel to each other and rotation is in parallel planes and in the same direction. Now, that makes each particular electron at a very small permanent magnet with north and south, north and south, north and south poles. And that's the reason why south and north are attracting each other because if we will turn it around, their direction would be opposite and would be south to south or north to north and that's why there is a repelling force between the same poles. So different attract the same repell. So this is how our magnet looks inside. All axes are parallel and all planes are parallel and all rotations are in the same direction. Now, again, let's consider the axial view, view along this direction. This is my view. So what happens? Here is what happens. You see south and north? Well, if they exert certain magnetic field, certain force, these two forces they are attracting to each other and basically neutralize each other. It's like there is no force. And what remains? What remains this north and this south because these are already closed on themselves. Okay, but there is another one here, right? North and south. So these two are also neutralizing each other. Now, if you will go all along these parallel axes, one under another, what will remain? Remain only the most, well, in this particular picture, the one which is on the bottom and one which is on the top. And same thing here. So you will have all north by themselves, not paired with the south, and all south by themselves, not pairs with the north. On two opposite sides of permanent magnet. And that is actually how the permanent magnet looks like, right? This is north, this is south. Basically all the forces are here. And this picture explains why magnetism, if you will take a nail for instance, the nail will be mostly attracted to these two extremes, to poles, to real poles. And the attraction in somewhere in the middle would be significantly less because we are further from this and closer to this one. But so it would be actually weaker than if the nail will be here. And if you will move it to the middle, then the attraction will be the same from both sides. And you will feel practically no magnetic force. So this model explains quite well the properties of permanent bar magnet. Well, actually if it's not a bar, but if you will turn it into a horseshoe, for instance, it's exactly the same thing. You just turn the whole thing picture, but inside you will have exactly the same thing. So this is the model which was introduced somewhere in 1600 by the person with the name Gilbert, Englishman, physician, by the way. And he wrote a very interesting, I think it was like six-volume book where he presented all the contemporary knowledge about electricity and magnetism, and that was his explanation of the magnetism. No, he didn't know the electrons. He was just thinking that there is something going on which basically causes the concentration of real magnetic force on two poles. Yeah, I'm not exactly right when I'm saying that he offered exactly this model, but in any case whatever he has offered grew into this. But he offered that these inside things are basically nullifying each other and only outside two extremes of the magnet remain unpaired, and that's what's causing the polarity. By the way, one particular element which has two poles is called dipole. So the electron is the smallest dipole, and in this particular case, the case of the permanent magnet, all the dipoles are aligned properly and that's what makes the magnet to have its magnetic properties. Alignment of dipoles. Alignment of the axis. Alignment of the planes of rotation and alignment of the direction of the rotation. Okay, dipole. It also explains another interesting thing. What if you will cut the magnet in the middle? We were talking about basically that it creates two different magnets north and south. You cannot get rid of the poles by separating the magnet in the middle. Why? Obviously, because if you will separate it here, let's say, like here for instance, you will have south poles unpaired here and north poles unpaired there and that's why you still have north and south, north and south. So it's a very good model which explains these type of things. Now, more than that, actually if you will consider that something which we will call magnetic charge, like equivalent of the electric charge. So these two are magnetic charges concentrated at the very ends of the magnet. Now I'm using quote-unquote magnetic charges. Then you can probably apply something like an equivalent of Coulomb law to this type of configuration. The only thing is, we have two different sources of forces. In electricity it's kind of simpler because we can isolate only plus or only minus charges and we can consider a point charge. Here we cannot consider a point charge. There is no such thing as a point charge. There is always a dipole, I think, which has two poles. So each pole should be considered separately and probably the Coulomb's law. It's like superposition of two different magnetic fields. One magnetic field from this and another from this. And you can use an equivalent of the Coulomb's law. The only problem is we don't really know with magnetic charges how to measure it, etc. So we will come to this a little bit later. So, okay, this is the Gilbert model of the magnetism and that's one thing which explains quite well and now we will talk about a different model. Now we will talk, we were talking about axial view, right? Now we will talk about planar view. So you have once more the same picture. All electrons are rotating in the same direction. Axes are parallel, planes of rotation are parallel. So what happens here? Planar view, okay? This is going this way. So these two electrons near each other within the same plane are rotating against each other. Now if you will view the whole thing from the top, you will see a circle. This is the orbit of one electron. This is orbit another, another, another. So what happens if all of them are rotating in the same direction? In these points they are rotating in opposite direction. You see? Whenever they are touching each other, well touching is obviously not a proper process whatever is happening, but we are near each other. Whenever they are in the same plane and you will look from the top to this plane you will see that all these points are the points where electrons are moving to opposite direction. Right? Like in this particular case. And if this is another orbit you will have direction is the same. If you will look from the top it's always counterclockwise on each one of them. But at these points they are moving into opposite direction. So moving electron is a current, a small one but still a current. Now these two electrons which are moving into different direction basically represent that there is no current, there is no movement of electrons in some particular direction. So it looks like again let's consider view from the top. All the inner connections between these orbits are where there is no current. And where is the current? Well if the whole view from the top contains only these four orbits you see only on the outer surface all electrons are moving in the same direction. So it looks like if you will have a permanent magnet it looks like you have electricity which is actually coming around the side surface of this magnet. And there is absolutely nothing inside because nothing inside electrons are moving into different direction and they again neutralize each other. There is no flow of electrons into any directions. The flow of electrons only around the surface of this. So basically what you can say is that the movement of electrons let's just forget what's happening inside. Let's just concentrate only on the outside. So we have a macro object now. A macro object not an electron. The whole big permanent magnet which has electrons moving around its surface only. So these are circular orbits. Well not exactly circular depends on the shape of the magnet but in any case it's only on the outer surface. And that's what makes magnetic force here. Now this is a very important model. This model belongs to Amperage. The guy whose name is measurement of the current flow of the current Amperes. So Amper was actually the author of this model. And what this model gives us it gives us direct connection between magnetism and electricity which is basically kind of flowing on the surface of the magnet. Which means that if I will take a loop of electric wiring from the top, if I will take this loop and this is plus this is minus what this loop should produce it should produce magnetic field which is directed perpendicular to this picture. Now view from the side would be something like this. So if you have a loop and these are wires plus and minus then this electric loop will produce the magnetic field which have north and south north and south magnetic field. So electricity, the loop of electricity produces the magnetic field which is perpendicular to the plane of rotation. So again this is extremely important because it makes a macro connection between electricity and magnetism. And this is why we are not talking about electricity by itself and magnetism by itself we are actually talking about electromagnetism as one kind of a subject it's one field of research and study because electricity and magnetism are always together. Any loop of electricity is producing certain magnetic field and that's what's very very important. It's also important in some other aspects. Well the aspect number one measuring the electric characteristics we can basically measure the magnetic characteristic if we know that this loop is equivalent to a magnetic dipole then we can have certain units of measurements of the magnetism based on the units of measurements of electricity and maybe some geometrical properties of this loop. That's one thing. Another thing is that we can produce magnetism artificially you don't have to use the permanent magnets whatever their strength is we can use artificial magnet by very simple mechanism. We can have something like a base whatever the base is metal rod, nail, whatever you want and put a wiring around it and connect it to plus and minus and this particular loop of electricity will convert this piece of iron into magnet. Why I'm talking about piece of iron? Well iron has such a property that by itself it does not have any kind of magnetic properties. All the electrons inside are chaotically positioned they're not aligned so it's not a permanent magnet. However if you have some force, magnetic force applied to this piece of iron for instance you take it close to a pole of permanent magnet for instance magnetic field of the permanent magnet will align the electrons inside this iron bar and since they are aligned it becomes a magnet so you know that if you have a magnet here permanent magnet and you put let's say a piece of metal let's say iron, nail or something but not only it will be attracted to the pole now if this is south pole now this will become north and this will become south pole temporarily of this iron nail or something and something can be attached now and one nail will be attracted to this pole and it will also become magnet. Well it will be weaker and weaker but in any case the whole thing actually would work so iron is such a metal that converts under the influence of the magnetic field it converts into magnet because its axes are not aligned in the beginning but under the influence of the magnetic field they are aligned so that's how we can make artificial magnet put the wire loop around and this thing will become a magnet because the wire is a magnet the loop of the wire with current going through this is a magnetic dipole and it will force the axis of electrons inside the iron to align properly but why don't we just take more than one loop why don't we just take another one and another and another the more loops of electricity of electric current we put around it the stronger we will have these electrons inside this iron bar to be aligned more electrons will be aligned the stronger magnetic field is the stronger organizing force will be applied against the electrons of this piece of iron and the stronger magnet it will become this is called electromagnet we are artificially creating from something which is not magnetic by itself but it has a property of being a subject of alignment under the magnetic field forces so we are forcing this particular piece of iron to become a magnet but obviously the proper way of doing this is you don't have to have the individual loops what you can have is a loop around it plus and minus and that would be the proper way of making an electromagnet so if you will make a very small experiment you will take a nail and put around it copper wire and connect it to some kind of a battery then your nail will become a magnet that's very easy to experiment with ok so my important point here is electricity and magnetism are connected now emperor's model actually gives us the reason you remember the reason? if you will take a look from the top onto the magnet all these electrons are here and all these orbits all axes are parallel these are axes of rotation perpendicular to the board and rotation is to the same direction but all inside currents will go against each other as if they don't exist at all and only the outermost current is present and that's what makes a magnet a magnet and that's why this flow of electrons on the surface will make these magnetic properties now the permanent magnets already have this and the something which is not a permanent magnet is something like an iron which can become a magnet under the influence of the magnetic forces we can make it magnetic by putting a wire around it so that's it for today electricity and magnetism are connected and we can measure one with another and from now on the term electromagnetism must be understood as this is something which is one particular subject of study and research it's not too individual one because every magnetic field is caused by some kind of electricity going somewhere maybe inside, maybe outside but there is something which is definitely going on with electricity so each magnetic field is the result of electricity and also electric field exists in the magnetic in the permanent magnets so again it's interconnected there is no such thing as one and not another they're always together that's why this whole subject of the course is called electromagnetism and by the way emperor's model it plays much more important role than Gilbert's model when you have just two magnetic charges on two different poles because it has a lot of practical implications obviously lots of electromagnets are used in our economy I mean electromagnetism is everywhere and that's something which we will talk about on some other time thanks very much and that's it for today, good luck