 Hi, I'm Zor. Welcome to Unisor Education. We will talk about magnets, continue talking about magnets. Now this lecture is part of the course, Physics for Teens, presented on Unisor.com. If you've found this lecture on YouTube or somewhere else, I do recommend you to go to Unisor.com because the lecture is actually part of the course. So you will see the whole hierarchy of different topics and every lecture has very detailed notes, like a textbook. The site has exams and the site is completely free, no ads, no strings attached. So let's talk about magnets a little bit more. Now this is an unusual lecture for this course because primarily in this course I'm trying to stick to theoretical part of the physics, which means formulas, certain laws, etc. Now today's lecture will be about practical usage of magnets. Now why I have decided to do this? I didn't discuss very much practicality of electricity. However, it's kind of obvious what we are using electricity for. With magnets, it's not as obvious and in many cases the usage of the magnets is hidden and that's why I would like actually to put it on the surface. So first of all, there is a very long list of different applications of magnets in the notes for this lecture. I will just mention a few of them. Well, everybody is using a screwdriver and you know that there are magnetic screwdrivers, which means if you just touch a nail or a screw or whatever, it sticks to it. That's the magnet. That's a permanent magnet inside the screwdriver. Now everybody heard about MRI, Magnetic Resonance Imaging. Well, that's a magical device, very complicated device and it's using magnets to basically make an image of let's say your brain or something else for diagnostic purposes. Now in computers, it's used extensively in many many different places. Now those a few who know, who have kids actually, there are magnetic toys. So my grandchildren, for instance, built whole buildings from certain magnetic blocks. They're sticking together. What else? Well, obviously in all the motors, electric motors and electric generators, magnets are used very extensively. I mean, they are in the heart of these devices. Well, everybody knows about compass, obviously. So these are just a few applications where magnets are used. There are many many many more. Now magnets do occur naturally, like we can find it as a rock basically. Now, and that's how they were basically first found and kind of were subject to curiosity, I would say, because these two rocks, they can either attract each other or repel each other depending on which side you turn it. Now, what are these? These are called magnetites. Magnetites and it's iron oxide actually and the chemical composition is ferrum 304. So every molecule has three atoms of iron, ferrum and four items, atoms of oxygen. So that's the naturally occurring permanent magnets. They are weak. Now, we also have the ability to do artificial ones. Now, before we have this kind of technology to do the artificial magnets, people were using whatever was available and how these permanent magnets, which occur in nature, how they were used. Well, for example, if you just hang this rock on a thread, it will turn along a region like a compass because it's a permanent magnet. What is a compass? This arrow inside the compass is a permanent magnet. It has north and south and one of the poles is pointing to north and other to south. Same thing with this. Any permanent magnet just left by itself will turn along the meridian line because the earth is a giant magnet. Now, another way how you can use the same quality is if you can in some kind of reservoir with water you put a plate which is floating and put this piece of rock on this plate. So it just can turn in any way just floating on the liquid. It will do exactly the same as in this case. It will turn towards north-south direction. So these are the usages and obviously as I was saying, this is a very weak permanent magnet. Then we have learned how to make artificial ones. Well, basically, again, it's kind of a composition of certain elements. It's an alloy. Obviously, the main component is iron of this alloy and one of the strongest artificial magnets, permanent magnets, is called, it's a very difficult word, well, there is an element, neodymium, and if you add this element to iron and maybe something else, I don't remember, I think, cranium or something. I don't know. So you will get this shiny piece of metal. Basically, it's alloy which has a very, very strong permanent magnetic qualities and there are many applications for this and these are really strong even the little tiny like ring made of this material is very, very strong magnet. And by the way, you can purchase them on the internet. Now we can do different things. We can do different form and shape of artificial magnets. I mean, everybody knows the U-shape magnet, right? One part is north and other part is south. Obviously, the bar shape, one part is north and other is south. You can have spheres, you can have rings, you can have many different kinds depending on the application. For example, if you have rings, for instance, and then you have some kind of a stick and you put rings on the top of another, if you put them in direction, so if this is a ring and you have one surface north and bottom surface is south and you will put them one on the top of another. If you put that in this sequence, they will stick to each other, but if you will put it in this sequence, this is one ring, this is another ring, this is third ring. They will repair each other because north to north and south to south will repair and they will be hanging one on top above the other, right? So these are different little experiments, basically, which prove certain magnetic collages. Now, what else? What's interesting is, let's talk about bar magnets. Now, you can feel the strengths of the magnet by having, let's say, metal paper clip or a nail and just stick to this particular place, which is a pole, one of the poles, north pole, for instance. Then, if you will stick into this position and you will feel how it pulls your nail, you will feel that the magnetic strength is a little bit weaker and at this point in the middle, it will be just zero, basically. There will be no strength at all. And then, as you move further to the another pole, again, strengths will be great. So, this is kind of a representation of the strengths of the force. Now, why is that? Well, obviously, this part is magnetic in one direction and this part is magnetic in another direction. So, if you have this nail in the middle, then it's like pulling into two different sides with the same strengths and then basically nullify each other. And that's why you have no magnetic properties in the middle of this bar magnet. Now, what happens if you just cut this magnet in the middle? Will you have only, you see, this is the north part, for instance, this is the south part. If you will break it in the middle, will you have only north in this particular case? And only south in this particular case? No, absolutely not. So, if this is north and this is south, this is north, this is south, this is north, this is south. So, every piece of this will have two poles. And it's related to, basically, the reason why magnetic field exists and that we will discuss it in the next lecture. But that's what's happening. So, there is no such thing as a single pole permanent magnet. It's always two. And if you divide it in half, you will still have two pieces. Obviously, these will be weaker. Each of these will be weaker than this one. Okay, what else? Now, permanent versus temporary magnets. So, there are temporary magnets. Now, your nail, if you stick it to the magnet, the permanent magnet, this is your nail. It becomes actually a magnet by itself, because now you can have a paper clip and attach it to this part and it will attach it. It will magnet, it will basically attract it. So, this becomes a continuation of this. So, this is some kind of a magnet, permanent magnet. Now, this nail becomes a temporary magnet. So, if this is a north pole, then this will be a south pole and this will be north pole on the nail. And that's why you can have this paper clip attracted to this, because paper clip itself becomes, again, a little magnet with this south and this north. And north to south and north to south are attracting to each other. So, that's what's happening. But this is temporary. As soon as you disconnect it, the orientation of atoms inside the paper clip or or a nail will become chaotic again, and it will lose its magnetic properties. So, the difference between permanent and temporary magnets is that the permanent magnet has permanent magnet has the same orientation of atoms inside. And we will talk about this in a little bit more details when talking about magnetic fields. Now, the soft metals like iron, they do have some kind of a chaotic chaotic position of its atoms inside. They're not oriented the same way as in a permanent magnet. And that's why as soon as you disconnect them, there is no force which brings them in order. So, they become, again, chaotic and lose their magnetic properties. So, by themselves, they will not possess any magnetic properties. Although, I should actually have to say that in this case, it's not exactly like they're immediately lose their magnetic properties. I think during a certain very short period of time, while all these atoms inside the nail are, again, becoming chaoticly positioned, it takes some time. And while this time lasts, certain magnetic properties will retain, although less and less. So, in a short period of time, it will completely disappear when all the atoms become, again, chaoticly positioned. So, these are temporary magnets. And obviously, there are things which are completely not capable of being magnetized. Like copper, for instance, doesn't really have this kind of a property. So, whatever chaotic position of the atoms inside the copper exists, magnetic properties of the permanent magnet doesn't change, doesn't orient the atoms inside the copper. Next. Next is a very interesting, at least for me. I mean, I'm old enough witnessing the first computers. Now, the first first computers, they needed some kind of a memory. And the memory was organized. Each bit of memory, zero or one, was actually written on a small ring. It's called ferrite or ferrite ring. And if you have, if you have to have, for instance, one byte of information, which is eight bits, so you have eight rings on the wire. And there are actually different wires. One wire sends an impulse and these rings, this ferrite material, it's such an interesting thing. If you put an impulse through this ring, it will magnetize in one direction, like north in one side and south in another side. If you will send an impulse in another direction, it will magnetize differently. And that's what actually zero and one meant. So, obviously, you understand how much weight and space this memory occupies. I mean, it's huge. So, I do remember actually seeing this ferrite rings as a memory. Nowadays, it's completely different. However, magnetic disks, which we are still using, they are using a layer of certain substance which has certain magnetic properties. And you can again write on it or read from it. And that means you are orienting atoms on this surface, on this magnetic surface of the disk in one or another way. So, that's basically the same principle as with this. It accepts that our memory bits are not in ferrite rings, but on a molecular level, basically, or almost molecular level, very, very small. So, that's about computer memory. What else? And magnetic tape. Everybody knows what magnetic tape is. Remember, the sound was recorded on magnetic tape before something a little bit more advanced appeared on the market. And the last one, which I... Yeah, even the liquid, yes, even the liquid can be made in such a way that it has certain magnetic properties. And there is certain medical technique to inject magnetic liquid with magnetic properties inside the tumor. And then, using external devices, you can heat up this liquid because it has these magnetic properties. And the heat actually kills the tumor. And at the end, I wanted to spend some time, actually, for something which is, I think, very interesting. So, everybody knows about gravity. Gravity exists. I mean, it looks like it's some kind of a very unusual kind of energy because it does not really disappear. You cannot spend it somewhere or another. It's always there. So, it looks like it's kind of a way you can use to create some kind of a machine which will be just moving all the time based on these properties of gravitation. Now, magnets are exactly the same, except it's much easier to manipulate because it's much stronger than the gravity. So, people were using magnets to build some kind of a perpetum mobile, machines which are moving constantly, for instance, can generate electricity, if that's true. And, well, let me just give you one small example. Now, there is an example which I put in the notes for this lecture, but this is another one which I kind of like. To tell you the truth, I don't know exactly all the details why it's not working. It's not working because it contradicts the conservation of energy principle. However, it's interesting. Consider this type of a wheel, let's say. And on the wheel you have a chain of metal balls, let's say, connected to each other. Now, by itself, obviously, it does not rotate. Now, there is an axis here. However, what if you will put a magnet here? Well, it looks like this magnet is attracting these balls, much more than these balls. So, why aren't they moving? Why isn't that rotating the whole thing? Well, I mean, first of all, you can very easily make this experiment yourself, and it will not move. Now, the reason is that there are many different forces here. There are forces which are attracting here, but there are forces which attract from this. Now, how can you turn your magnet in such a way that it will attract these more than these? It looks like it's possible. Actually, it's not. So, no matter how you do it, it will always be in the position that nothing actually moves. Now, there are much more ingenious devices. And the one which I put in the nodes, it looked like the car engine. So, if you have, let's say, one cylinder, which is supposed to be up and down. So, if you have a magnet which is here and here. Now, this would be always north and south. Now, what if you will put south here? It will go up, right? Because north and south will. But while it's going up, we will turn it around. Let's say we will connect movement of this part with rotation of this part through some kind of a crank mechanism or whatever. So, as soon as this one reaches the top, this one will turn around and instead of north-south, it will be south-north. Then it will start repelling it and it will push it down. So, if you will synchronize it in such a way, then it looks like it should move by itself. Well, it will move by itself for a while if you will start this movement somehow. But then the friction and some other things will stop it. So, again, all these attempts are very interesting from kind of a hobby standpoint. And if you will go on Internet and YouTube, for instance, you will find numerous examples of machines which seemingly work by themselves without any additional source of energy. Well, generally speaking, none of that would work. However, it's, again, a very interesting hobby and I do recommend you to make this search. It's just very kind of, it's a very good thing to satisfy your curiosity. Alright, so basically that's it about magnets. I think next lecture will be much more theoretical, which I would personally prefer. But this is, again, some kind of an interesting fact about magnets and I thought to share it with you. Thanks very much and good luck.