 Hi, I'm Zor. Welcome to Unizor education. I would like to start a new chapter of this course which is dedicated to electricity and magnetism. Now this chapter, this part of the course is basically part of the physics for teens course, which is presented on website Unizor.com Another course which is prerequisite for this one is math with teens also on that site. All courses are completely free and there are no advertisement on this website, so I encourage you to watch this lecture from the website for many other reasons, but the main reason is that it's a course. It's not just one lecture which you can find on YouTube. It's really something which has certain logical sequence of lectures with certain dependencies, etc. Plus, every lecture has very detailed notes, which basically can help you. It's like a textbook, basically. So you can read the notes or you can listen to a lecture. It's inherently the same type of information. Plus, on the website, I also have exams for those people who would like to take them and again, there is absolutely free everything. So I do suggest you to go to Unizor.com and take the course in whatever the sequence is presented. Now, the math with teens is relatively complete, although I do not have certain exams in some cases, but the theoretical material is complete. Physics is being created as we speak. So right now, I'm in the beginning of electricity and magnetism, or electromagnetism, chapter of the course, and I will start, you know, I will record different lectures as we go, basically, as the course progresses. Now, so the first lecture in this course is basically about some basic, very, very fundamental things about electricity. Electricity is a form of energy, and as a form of energy, it should have certain substance behind it. Now, if it's a mechanical energy, the substance behind it, or objects behind it, are moving objects. The motion itself is the motion of the objects is carrier of mechanical energy. Now, if we are talking about, let's say, thermal energy, what is the source of thermal energy? Well, that's oscillating molecules inside the object. The faster they oscillate, the higher the temperature is. Now, there is some other forms of energy, like chemical energy, which is basically inside the molecules between the different atoms, which holds the molecules together. So, if we are talking about electricity, we have to have something which carries electricity, which is actually the substance based on which we can talk about electricity. Okay, so here is what it is, and I'm sure you know about this. So, all objects are built from molecules. The molecule is the smallest part of the object, which still carries the characteristics of this object, primarily, like chemical characteristics. So, the molecule of the water is water. Then we go deeper into the molecule, and we find that, let's say, a molecule of water contains two atoms of hydrogen and one atom of oxygen. Now, hydrogen and oxygen have nothing to do with water. These are atoms from which if they are combined in the proportion, as I was just saying, we will get the water. But atoms are deeper on this scale than the water and than the molecules, and they do not have the same chemical characteristics. Okay, let's go in deeper into the atom. Now, according to the classical theory of how the atom is actually structured, and this is not exactly how it is in the real world, how God created, for instance, the atoms. We are talking about a model of atom as it was, like, classically established in the beginning of the 20th century by Niels Bohr and some other physicists. So, the classical planetary model or orbital model of atom is that there is a nucleus in the middle of the atom, which is basically carries the most mass of the atom. And on the orbits, there are certain electrons. So, this is the orbital or planetary model of atom. Now, Earth is rotating around the Sun, right? Now, what holds Earth on the orbit? Well, the gravity. The gravitational force between Sun and Earth is something which is holding the Earth on its orbit around the Sun. Now, what holds electrons on the orbit around nucleus? Well, there must be some force. So, this is the electric force, which exists between the nucleus and the electrons. Now, more and more involved experiments actually opened up the whole picture as we more or less know it right now. And the picture is that inside the nucleus we have two different kinds of particles, protons and neutrons. Now, apparently neutrons do not play any role in holding electrons on the orbit. It's only the protons. And the number of protons is usually equal to the number of electrons which are circulating. Which basically prompts us to think that it's some kind of a force between the protons and electrons is what holds electrons on their orbits. And again, there were physical experiments which actually proved it. What's important is that proton and electron do attract to each other. However, proton and proton are not. They are repelling each other as well as electron and electron are repelling. But proton and electron are actually attracting to each other. So these are all results of the experiment. Which again, caused physicists to basically say something that, okay, let's just assume that there is certain quality which should be associated with the protons and electrons. And we will call this quality electrical charge. And considering we have this picture we can actually just, you know, conditionally call protons to carry positive electrical charge and electrons negative electrical charge. Well, obviously, this is a language. I mean, there is nothing like positive or negative when we are talking about real article. But it's a convenient model if we will associate the sine plus with the protons electrical charge and sine minus with electrons. It's actually very nice to view it this way because whenever you have them combined, one proton and one electron plus and minus nullify each other. And basically we will have a zero charge, which means we have a neutral, electrically neutral combination. Now, and again, if you have, for instance, if you have more electrons in the object than the protons, the whole object becomes more negatively charged because there are exes of electrons. If there is a deficiency of electrons, there are certain protons which do not have the corresponding electrons. So the whole object becomes positively charged. So again, this is the language charge, positive, negative. This is the language physicists are using to describe this property of protons and electrons to attract or repel each other based on whatever the combination is. Now electric force between proton and electron is really very, very strong. And I was doing some calculations actually which are presented in the notes for this lecture on Unisor.com. So if you will go to this lecture and you will watch it from the website, you will see side notes where I have these calculations. So I wanted to demonstrate how strong electrical forces are and how much stronger they are than, let's say, gravitational forces. So here is what I have done in these calculations. I took one cubic centimeter of iron, small, you know, cubic centimeter, and another cubic centimeter of iron. Place them on a distance one meter from each other. Now, let's assume, obviously we will never do it and it cannot be done, but let's assume just to demonstrate how strong electrical force is. Let's assume that all electrons from this cubic centimeter of iron are magically transferred to this one. So now this becomes very, very positively charged because there are no electrons. So there's a deficiency of electrons. So we have naked protons and here we have very, very negatively charged because here we have exes of electrons. All the electrons from here came here. Well now, since they are since they carry opposite electrical charge, they are attracting to each other. Well, question is how strong is the force which exists, attracting force between these two small amounts of iron. Well, imagine sun and the planets around the sun. So I took Mars, for instance. So imagine the force which exists gravitational force between sun and Mars. This gravitational force keeps Mars on its orbit, so Mars doesn't really fly away. Considering the mass of Mars, this force must be very, very significant, obviously. So these are comparable forces. So the force between these two cubical centimeters of iron, in case we strip all protons, all electrons from this to this, this force is about the same. I mean, it's the same order. I mean, it's a little bit different, but it's the same order than the force which holds Mars on its orbit. So it's huge, actually. And I have a number. It's 1.11 times 10 to 21st Newton. 10 to the power of 21. I mean, huge. But obviously, this is only if we strip all the electrons from here to here, which never happens, obviously. In practical life, we strip very, very tiny amount of electrons when we are transferring from one to another, if it's possible to transfer. Okay, now how is it possible to transfer electrons from one to another? Well, if you have, for instance, two objects of different kind very, very close to each other, like rubbing them with each other, then sometimes certain amount of electrons can actually fly from one object to another, which means one object will become a little bit positive and another will be a little bit negative. And between them, there will be a little of electric force. Now, I was actually trying to experiment and let me try if it will work. So I have, I have this little piece of aluminum foil. I hope you see it. And I have a small plastic stick. So right now, this is aluminum foil, you see? I'm touching it, nothing happens, right? Now, what if I will just rub this particular piece of plastic against some close or whatever. So let me try to do it right now. Oops, oops, you see? Now it's moving. It was not moving before, now it's moving. Why? Because when I was rubbing with the close against the plastic, certain number of electrons transferred from one to another. I don't know from which to which, doesn't really matter. But now the plastic becomes a little bit charged. Now, when I move it closer to something light, like this foil, for instance, let's consider this is negatively electrically charged. I don't know exactly, but for instance, explanation is exactly the same. So there is an excess of electrons. Now, what happens when I have excess of electrons here? Well, now here there are protons and electrons in exactly the same quantity. This is neutral. Now, when I am moving this closer, electrons here and electrons there are repelling each other. So some of the electrons within this aluminum foil are pushed by this repelling force further. And whatever remains closer are more protons than neutrons. So this part of the object becomes positively charged and this part of the aluminum foil becomes negatively charged. Just because I'm coming closer to this particular foil, it redistributes electrons inside. Here I have an excess. So these electrons here are pushing electrons inside the aluminum foil towards the other end and whatever remains on the closer end is deficiency of electrons. So excess of protons, which means it's positively and this is negatively so they attract each other. So this is the manifestation of how electricity is actually working. So electrons are the carrier of electricity. Absence of electrons means that somewhere there is an excess of electrons in other places. So then we can talk about electrical charge and as long as electrical charge is not equal to zero, I mean it's not neutral, then there will be certain electrical force between the objects. So whatever I just showed to you is basically the reason for a device called electroscope. So let me take it off. So what is electroscope? Electroscope is a device which looks like, let's say you have some kind of a glass. Now here you have a cork, let's say. Now you have a metal disc on the top and this is also metal. And at the end you have the same two aluminum pieces of aluminum foil, they're just hanging. Actually it can be anything, even the plain paper actually will work as well. Now as long as this particular system is in neutral state, there is exactly the same number of protons as there are electrons, now these things are actually hanging down, vertically down. Because there is nothing which basically moves them apart, they're just hanging down. But if I will do something like I did right now, I rubbed some glass or plastic against some clothes or whatever it is and I have certain electrical charge, again let's say for instance this is a negative electrical charge which I have achieved by this rubbing or whatever. Now if I will touch this metal thing, then electrons from my electrically charged stick will touch the surface. Now I have an axis of electrons, here we don't have an axis, here we have a completely neutral charge. So certain electrons will just flow from this stick into this metal rod and now we can talk about the conductivity, metal is a good conductor of electrons. So electrons will travel down to this rod and now we will have axis of electrons in the whole system here. Now considering these are two free-hanging aluminum foils and they are both basically negatively charged, they will take this particular position because they are repelling each other. And the stronger the charge, I mean the more electrons I have in my stick which are transported into this metal rod, the higher will be angle of these two aluminum foils. So you can actually arrange some kind of a measuring tool using something like this which basically shows you how strong electrical charge is which is transferred from some source into this particular device. Now what other manifestation of electricity I can exemplify? Well for instance obviously everybody saw the lightning, what is lightning? Well it's not just simple electricity, I mean we can now see that lightning is actually a flow of electrons which are just shooting down from electrically charged cloud, let's say to the earth or to some kind of device, whatever we have, a metal rod maybe to protect the building, whatever it is. So there is a connection through the air between one particular object which is charged in one way and another which is charged another way. Now even if the ground is actually neutral so we have the same number of positively charged protons and negatively charged electrons. What happens if you have a cloud which is very very negatively charged? Well what happens is electrons from here will be repelled so electrons will go down. So plus will be here and electrons negative will be here because these electrons are repelled. So what remains now we have positive and this is negative so there is a very strong attraction. And that attraction actually is the reason why these electrons are moving down and go into the earth. Well the earth is big enough to accumulate a little bit more electrons from this cloud. But in this particular locality it's not such a small, I mean it's really a small area. So in that small area we have the difference between pluses and minuses, minuses go down, pluses remain and electrons are flowing through. By the way I'm not sure it's really minus and plus maybe it's really plus and minus, I just don't know but it doesn't really matter. Electrons either go this way or go that way but whatever it is it's an exchange of electrons between the objects. That's what actually carries the electricity. That's why the whole lecture is about carrier of electricity. It's electrons which are components of the atom. These are carriers of electricity. Alright, now obviously if somebody puts some kind of a fur coat you also, you hear or sometimes you can even see the little sparkles. It's all electricity. It's only because again something is rubbing against something else and as a result you have a separation between protons and electrons and on one surface you have a deficiency of electrons and on another you have an excess of electrons. And now when they are close enough sparkle between them actually moves electrons back where they belong. So that's what happens. So first during the rubbing we're separating, we're putting a certain number of electrons from one object to another. But then when the sparkle comes it basically goes the other way around and it neutralizes the whole thing. Alright, anyway this is a very, I would say, introductory lecture about electricity. I just wanted to know about electrons, about positive charge, about negative charge, protons, electrons, excess of electrons, deficiency of electrons. So that's basically all. And if you will take a look at the notes for this lecture on Unisor.com you will also see the calculation how I came up with this force between two cubical centimeters of iron positioned at one meter from each other in case we stripped all the electrons, how strong the force will be in this particular case. So that's it for today. Thank you very much and good luck.