 Hi, I'm Zor. Welcome to a user education. We continue this part of the physics for teens course, which is called electromagnetism Before we were talking about electricity. This is the first lecture, which will be talking about magnetism and Then when both of them will be finished, we will talk about why we are combining this into one electromagnetism part of the course now So the name of the whole course is physics 14. It's presented on unizor.com I suggest you to watch this lecture from the website from the unizor.com because Every lecture has very detailed notes. It's like a textbook There are many problems which you can just solve yourself and then check the answers if you are correct for self-checking there are exams and The site is completely free. There are no ads. No no strings attached. You don't even have to look in if you don't want to Okay, so let's talk about magnetism Well, first of all, recall that we had two very very different kinds of forces One kind of force is the contact. That's where we were studying this in mechanics If I'm pushing something that's kind of obvious What is the source of the force and what's the result of this kind of a movement? another Kind of forces where the forces which act on a distance Now so far we were talking about gravitational forces they do act on a distance and electrostatic forces Also act on the distance There are similarities and there are differences between these forces for example Gravitation gravity always exists So whenever you have any material object there is some gravity and gravitation always attracts two different objects in case of electrostatic Well, first of all in the forces electrostatic forces exist only if you have Charged objects charged means either they have an axis of electrons It's negative charge or deficiency of electrons. That's the positive charge So some objects do have this electrostatic forces between them some don't Which is different from gravitation Also in case of gravitation, it's always attracting in case of electrostatic It can be either attractive if you have positive and negative Or it can be repelling which you have two negatives or two positives So there are some differences. There are some similarities Now in both cases we have introduced a concept of a field Just to explain basically what does it mean to act on a distance? So we're talking about that there is some kind of a field We didn't go into More detail about what exactly the field is it's filled something which basically delivers the force That's that's kind of an explanation So the concept of field was introduced just to explain this Acting on the distance now In this particular Area we have just one other kind of forces Which act on a distance so not only gravitational not only electrostatic We also have another kind of forces and that's exactly what magnetism is about There are certain Objects which have permanent property permanent like In case of a gravity, but in case of gravity all objects have Which have mass they have gravitation around the gravitation field In this case only some object some object have some object don't have now the There are naturally occurring objects and we can also make artificial object of that kind so They have this property of Magnetism which is different from from gravitation different from electrostatic But nevertheless it acts in a similar fashion. So if you have for instance two Objects of this kind and we will call them magnets They can either attract if you just put them together properly or they can actually repel if you change the direction So it all depends on how you Direct these objects towards each other that that's one of the differences Well and there are some other less important differences what is important is that this is not related to any kind of Our activity you see electrostatic forces must be related to some activity first We should separate electrons from the atoms So wherever we go with electrons becomes negative and whatever is left Atoms without certain electrons become positive. So we need to do something to produce electricity In case of the permanent magnets, we don't do anything. They just exist It's like gravitation. Basically. It just exists so these objects and by the way sometimes they're called ferromagnetic ferro from the iron from ferrum ferrum that that's Latin and It's because all these objects are somehow related from the chemical composition to iron Or similar to iron like nickel for instance So These ferromagnetic objects, they are permanent. So we don't have to do anything To make it work to make the magnetic field around These objects to exist. So that's one thing they are natural and Permanent that's why it's called permanent magnets But again, we can artificially create chemically create these kind of objects, but they are they occur in in the nature so What is a very important is the following and again, that's kind of a differentiating this field The magnetic field around these objects from let's say electrostatic field In case of electrostatic field, it's either negative or positive. You don't really have in the same object both I mean, maybe temporarily you can separate them But if you don't separate it further then negative and positive will go back to each other and they will neutralize each other In case of magnet that does not happen It in case of magnets one part of this magnet is always have certain Magnetic properties of one kind and another part is from another part another another kind of magnetic properties and Conditionally again in as much as in electrostatic We call conditionally minus and plus negative and positive in case of magnets for the same object one part Is called north pole and another is called south pole and again every magnet has two poles Which is different from electrostatic Charged object when it's either negative the whole object is either negative or positive here The same object has two poles and as far as attraction and repelling is if you have Okay, this is my north pole and this is my north pole and these are south poles at the bottom so in case of magnets permanent magnets similar poles are repelling and Different poles like north to south or or south to north they are attracting each other so Again, there is some similarity and there are some differences What's important with permanent magnets is that the north and south poles exist on each object Why it's a different question, but that's what differs from let's say electrostatic forces now Okay, now what's very important is that Our planet Earth is a giant magnet It has also north pole and south pole Well interestingly enough North pole is Very close to our geographical north pole and south pole is very close to our geographical south pole in the planet Earth What's also interesting is that Location of the north pole and south pole is not really completely permanent because Earth has lots of things which are going on inside it It's volcanoes, you know all these lava things, etc. And Earth core is always kind of moving we live on a very thin crust above melted lava, basically So whenever it's moving Since everything is moving inside and there are all kinds of minerals metals, etc Melted together the location of the north pole and south pole is fluctuating Not a lot but sufficient amount of you know distance it's moving sufficient amount of distance to notice so We are using compass, you know to point to north or to south or whatever and I would like to say that if you are really relatively far from the poles somewhere, you know In between certain middle parallels Then direction of the compass to the north is Relatively precise, but if you are Here's our Earth Okay, this is the axis so this is our geographical north and somewhere here is magnetic North so if you are somewhere here in the middle parallels somewhere then That direction to the north pole Magnetic pole is really very close to geographic pole, but if you are near there You can have it in an opposite direction completely. So your north pole will be one direction and Magnetic north pole will be a completely different direction. So you have to be very careful to use the compass around the north pole or south pole and And the game the magnetic north pole and south pole are also fluctuating So you don't really know what's happening at that particular moment of time. So it's not not easy Now so how the compass is working well very easy compass has this kind of rotating arrow one of them is red Another is blue usually Now red is and It's the same actually for all magnets when they are artificially created or They're just from nature, but you're basically, you know buying it in the store. They're usually painted Half of them is painted red and half of them is painted blue blue is north Red is south. So what's happening red is south and points to? North pole of the earth north and south attract each other So that's why this arrow is this way and the north's Magnetic pole is over there then it gradually Directs to towards the north. So that's how the compass is working and Again, we have to really be very careful to use it near the north pole or south pole because then everything is completely different Okay, so that's basic properties of magnetic of permanent magnets Number one. They're permanent. We don't really have to do anything to Make this magnetic forces to actually appear to act They are permanent Secondly, we have two poles north and south conditionally called up this the north and south And north attracts to south But the repels north south attracts to north and repels south so in some way there is some similarity with electrostatic fields There are some similarities like permanence with gravitational field And again the difference is that they exist just by themselves You don't have to do anything to separate electrons, etc. Like in electrostatic field Like gravitation is it exists basically We don't know why to tell you the truth, but it exists same thing with permanent magnets now It would be probably interesting. Well, at least I consider it's very interesting to find out why the whole concept of Fields acting can the distance, etc. Why it it works this way And it's not easy quite frankly. I mean there are many theories for instance About why gravity exists In case of electrostatic fields we are attempting understand To understand the concept the mechanism by basically Talking about electrons access of electrons means negative deficiency of electrons means positive, but does it really explain this thing? No, because it's based on the fact that electron to electron Repel each other, but electron to proton. Let's say attract each other. Why? It's not easy again. There are many very interesting and very complex theories about certain More elementary particles being exchanged between let's say two electrons like imagine two electrons as Two people and there is a some kind of a bowling ball which one of them is Throwing to another so when the bowling ball is thrown then there is a recoil on one side and when the poor and the ball is Received on another side it's also by inertia Goes away from the first person right so they're really kind of repelling each other So if they are exchanging balls, they are repelling each other Well, it's an explanation. What are these balls? It's more elementary particles than electrons So if electrons are people then these balls which they're Exchanging is probably something really much much smaller than electrons and photons for instance So there are certain explanation. There are certain theories. There is a quantum field theory which basically spends a lot of time to explain certain things, but it's really very very difficult and Same thing with magnetic field there is certain kind of explanation which physicists are considering to be well relatively close to truth and Corresponding to their experiment and it's actually related to electrons and here is Very I would say superficial explanation of this So imagine an electron now the electron is not just, you know particle which Like a small ball or something like this it it rotates around the The nucleus of the of the atom and it also rotates around its own Access or at least we can hypothesize that it rotates which means it has certain spin Now as electron is spinning it's producing certain Magnetic field and this is by the way one of the Foundation of the fact that we are talking about electromagnetism Electricity and magnetism are related Electricity is related to electrons magnetism is related to the movement of electrons. So as the electrons spins If you have even number of electrons on the outer orbit around the atom they Have different spins half of them have one spin half of them have another spin they're rotating in one you can imagine as Rotating in one direction and another rotating in another direction and that produces The magnetic field but since they're spinning in different direction the magnetic field is Basically nullifying each other all these magnetic fields are nullifying north goes to south south goes to north North goes to south south goes to north and everything is basically neutral magnetically neutral But if you have an odd number of electrons on the outer orbit of the atoms and obviously, you know half of the Elements have odd number. Yes almost half Then we have a this balance then this one extra electron Doesn't have a pair So it's magnetic field doesn't really Neutralized by another electron which has a different spin So that's one of the reasons why this particular atom Can have certain magnetic properties, but this is one single atom if Atoms are positioned in such a way That direction of the magnetic Field of each atom is the same then all these magnetic fields of every atom are combined together and That produced north and south pole on the entire object So we need two Conditions to have this permanent magnet one condition is The material it's made of is supposed to have an odd number of electrons on the outer orbit and Also the atoms shouldn't really be completely randomly positioned inside the object They should be like a like a in the crystal for instance for instance. Okay, so there is certain Direction all atoms are Kind of directing their orbits So if you have all the orbits in one plane So all these planes should be parallel each other and positioned always in one direction Well To tell you the truth. I'm not satisfied with this explanation completely, but it's something It's something which also makes a very important connection Between electricity and magnetism electrons here and there Existence of electrons is for pure electrostatic, but their movement They're spinning or whatever you call it is the source of magnetic field That's why in theory. It's a one field called electromagnetic field and that's what we will basically study a little bit later Right now this part is for magnets only and their properties Okay, that's it for today. I suggest you to go to the website and read All these explanations. There are not too many things which I draw on the board It's mostly the text which is in the notes for this lecture, which I would like you to read it basically inculcates the whole concept of the field and How different fields? Gravitation electrostatic magnetic field how they are related as far as their properties are some of them permanent some of them require certain efforts some of them unidirectional only attracting some of them bi-directional and Basically existence of different kind of properties. That's it for today. Thank you very much and good luck