 Hi, I'm Zor. Welcome to a new Zara Education. We continue talking about electricity. In this particular case, it's a few lectures, actually, related to distribution of electricity. Before, we were talking about how to produce electricity. And basically, we were talking about converging rotational energy into electricity. Using electromagnetic induction. Now, we will just talk about different ways how to produce electricity from sources of energy which we have right now. Since the whole thing will be about distribution of electricity, we will talk primarily about massive production of electric energy on electric power plants. We're not talking about, like, little batteries. There is no problem in distribution of the electricity from a battery in your flashlight, for instance, to a lamp. That's kind of a simple thing. So, we are talking about real commercial producing of electricity and how it's distributed. Now, this lecture is part of the course called Physics for Teens. It's presented on Unisor.com. There is a prerequisite course on the same website. It's called Math for Teens. And I do recommend you to familiarize yourself with that. Both courses are completely free. There are no advertisements, no strings attached. So, enjoy. Now, distribution of electricity we will address in three different stages. First, at the source where electricity is produced. Then, the transit, how it goes from the power plant where it's produced to consumers. And finally, what's going on in the distribution area where consumers actually use this electricity. Now, this lecture is only about production. So, basically, electric power plants. That's what we are talking about. Okay, now, since the main way to produce electricity which we were talking about before was converting rotational energy into electric energy using the electromagnetic induction principle. We have to talk about how to do this rotation. How to produce a rotation which we can use in electric generator to produce electricity. Now, in practice there are many different ways and we will talk about three particular, probably the most interesting, most commonly used, and producing, basically, the most of electricity which we are consuming. Now, these three ways are hydroelectric power plants, fossil burning power plants, and nuclear power plants. I will very briefly address how it's all done on each of these plants. What's the main principle, if you wish? Okay, so let's start with hydroelectric stations. Now, hydroelectric stations are based on the principle of falling water which falls onto the turbine and the turbine is rotating and that's what basically is the main source of producing electricity, the rotation of the turbines. So, let's start from the beginning. Falling water, how can we get the falling water? Well, there are two different ways. Either we have it already occurring in nature like Niagara Falls, or we built a dam which will basically raise the level of water to a certain level and now we have a difference in two levels. So, in both cases we have water here, then some kind of a wall, whether it's a natural wall like in the waterfall or it's an artificial wall like in the dam, and this is the water on the upper level and this is the water on the bottom level. So, the water is falling. Well, obviously, whenever we want to build something it's not really like falling here. We basically just channel the water from here to here. Now, water here has a higher pressure because it's a higher level so the water goes through the channel here and now it can actually fall into the turbine, whatever the turbine is. I have a nice picture, by the way, of the whole hydroelectric plant and the picture of a turbine. Turbine is like a propeller, basically. We all know what this is all about. So, the turbine is rotating and rotating is then converted in the generator. So, this is a turbine, this is the water, falls on the turbine and here is the generator. And from generator we have electricity, usually alternating current. So, this is the main structure. Now, how can we improve it, let's say? Well, first of all, the higher the water the more energy falling water has and obviously more energy is produced by rotating turbine. Usually, we have not just one turbine, but a lot. So, we have the whole river basically stopped by this barrier. The water accumulates and then we can have as many turbines, as many fits to the blades of the dam, which we have built. The most powerful electric stations are hydroelectric stations and they are actually pretty efficient because the falling water just goes into the turbine and there is not too many other conversion of energy of one level of one type of energy into another. So, the efficiency of these turbines of these hydroelectric power stations is pretty high. Now, let's just very, very roughly estimate what kind of a power can we have. Well, most important characteristic is obviously how much water is actually falling per unit of time, let's say. So, let's say it's M, and that's kilogram per second in the sea units. Now, what's next important thing is the height. Obviously, the higher the water, the more energy it carries. The water which is on that level relative to water on this level has potential energy. Now, potential energy is measured by the height. So, we all know that if you have a certain mass raised at a certain level above, let's say, Earth or above any other level, the difference in potential energy is M times H. So, the H is very important. That's meters, right, in this unit. So, this is... Well, I have to multiply it by G obviously because we have to have a weight, not just a mass because Mg is the force. That's the force of gravity. And where G is the gravitational constant on Earth. So, Mg is basically the force. H is the distance. So, force times distance is work, right? Or energy in this particular case, which can be attributed to falling water. So, if we have M kilograms per second times G, whatever the... G is 9.8 meters per second square, right? That's the pre-fall acceleration. And if we multiply it by H, that's the total energy which we have. So, the M can be very easily measured because it depends on the size of the pipe, actually, which connects... Not all the water, actually, is falling on the turbine. We have this pipe, and the pipe directs the water straight onto the turbine, right? So, there is a certain capacity of the pipe. So, it depends on the speed of the water and on some other factors. So, M is definitely going to be estimated. And H is also estimated. That's the difference between the levels, between the turbine and the top level. This we know. Okay, so this is basically a theoretical maximum which we can extract from the water, right? Now, in practice, obviously, there is a certain amount lost. So, the power which can be generated by the turbine is some kind of a coefficient we have to multiply by total amount of energy which we can extract. And this coefficient is pretty high for hydroelectric station. It's something like 0.9 approximately, right? So, which is good. There's a good thing about this. Another good thing is we don't really spoil the atmosphere because whenever you're burning something like coal or nuclear, for instance, there are some... something which we actually... we spoil the nature with something which is the product of this process. In this case, we don't really spoil the nature. The problem is that, well, in case if it's a natural waterfall, we basically don't do much damage at all. But if we build the dam and the water is rising, it actually floods whatever the area in that particular place is. So, we are changing something. So, we should not really be very aggressive building the dams because it really spoils a lot of other things around the river. If it's a waterfall, then it's probably okay to use this energy in the falling water. So, the problem is, I mean, how many waterfalls do we have? Or rivers for the same thing. So, the energy is relatively limited which we can produce using hydroelectric station. In every case where it's possible, we extract as much as possible. So, that's why the hydroelectric stations are the most powerful. But in other cases, well, if there is no river around and there is no waterfall, well, what we do? Well, we resort to other sources of energy. So, the next thing is which I will talk about is the fossil fuel burning stations. Now, this is not as efficient, not as environment friendly as a waterfall-based hydroelectric station. But nevertheless, we don't have a choice. We need energy and hydroelectric cannot really supply as much as we need because there are not too many rivers and not too many waterfalls. So, the next thing is coal burning. About one-third of all the energy which we consume on this planet is produced actually by burning some fossil fuel. In most cases, it's coal and in many cases, it's oil. In some relatively recent time we started burning gas, also natural gas, to produce energy. Now, what's the common thing about all these? The common thing is that we are producing heat by burning something. And it's the heat which can be then produced into kinetic energy of rotation of a turbine. How? Well, the very simple thing is if you have water, this is reservoir of water, and you have some kind of a heat here, then the water is boiling, it produces steam, and steam can be directed anywhere we want. That's the way how any fossil burning electric power station is working. They boil water. In most cases, there are certain exceptions, but in most cases they just boil the water using the heat. So, it's not a direct conversion of kinetic energy into electric energy like in hydroelectric power stations. We have to produce kinetic energy, kinetic energy of the steam, and produce using the heat boiling the water. And that's where the whole problem actually is. That's where we lose a lot of energy by converting heat into kinetic energy of the steam, and we have certain products which we are like exhaustion and stuff like this. In case of coal, for instance, coal is basically a carbon. It's connected to oxygen in the atmosphere producing carbon dioxide. So, that's the problem. That's where all these greenhouse effects are. Plus, we are basically taking away oxygen from the atmosphere. Obviously, we need plants to reproduce back the oxygen from the carbon dioxide. Then we are cutting the trees for other purposes. So, that's the environmental problem. However, again, we don't have a choice at the time. One third of all energy is produced by this type of fossil burning. Coal is probably the major part of it. Oil is less. Gas is starting relatively recently. It's increasing in usage. But again, it's all burning. It's all conversion of heat into kinetic energy of the steam. The steam is directed to turbine and the turbine rotates and that goes to generator and generator produces the electricity. Now, how to make it more efficient? More efficient burning can be produced, for instance, if it's a coal, by basically pulverizing it. We are making a fine powder out of the coal first and then it goes into the burner. It burns better, cleaner, so to speak. So, this reaction is cleaner and there are other things which are actually produced by burning coal. It's not really clean. Well, the cleaner the coal, the better, obviously, it is as far as the environment is concerned. But it's never really clean. So, we have all other kind of problems related to these environmental problems. But again, the problem is we need energy and this is available and there is no choice, basically. Okay, so that's about coal. And the last one which I wanted to talk about is nuclear. Now, however scientifically nuclear power plant sounds, it's still exactly the same principle. We are converting heat into boiling water and boiling water produces steam and steam goes to turbines. However, it's the difference between this nuclear power plant and let's say coal burning is how do we make the heat? In case of coal burning, we just burn coal. In case of nuclear power station, we have a nuclear reaction. So, what is the nuclear reaction we are talking about right now? There are many different variations. I will just talk about something which is one of the most commonly occurring situations in the nuclear power plant. The kernel of the core of the nuclear power plant is a certain amount of uranium or plutonium which have certain properties when we are bombarding the nuclear of these elements with neutrons. Here is what happens. If you have uranium, I'm talking about uranium with 92 protons and the total number of protons and neutrons which is the atomic weight is 235. So, which means we have what? How many protons we have? 143, right? Neutrons, I mean 92 protons and 143 neutrons. That's what makes 235. Now, this is an element which has certain properties and what the property is? The property is if we will bombard it with a neutron. Neutron is just one neutron and zero protons. What happens? Well, first, the nucleus of uranium is absorbing this neutron and now it's 92 protons, the same number of protons because that's uranium which has 92 protons. It determines chemical properties. Number of protons determines chemical properties because it's the same as number of electrons on the orbits and that's how the chemical properties are actually determined by the number of electrons on the orbits. But it has one neutron greater. So, this one has 143 and this one has 144 neutrons because this one is absorbed. Now, the problem is this thing is not stable and here is what happens. It actually breaks. It cannot really exist. 92 protons and 144 neutrons in one nucleus cannot really exist. Why? I don't know. I mean, there are certain models of how it works, etc. Some connections, some forces, intra-nucleus forces which are working. But anyway, it breaks. Now, how it breaks? Here how it breaks? It breaks in many different ways. I'm just talking about one particular way how it can break and maybe most commonly occurring, I don't know. 139 barium, 56 plus 94 krypton, 36 plus 3 neutrons plus gamma energy. Okay, here it is. Nucleus of this isotope of uranium which has one neutron greater than this one. So, it's unstable. It breaks into barium. Nucleus of barium has 56 protons and whatever, like, what? 73 neutrons. And so barium is metal, actually. And krypton is a gas, it's a noble gas. It has 36 protons and the total number of protons and neutrons is 94. That's atomic weight. But if you will count, then the number of protons exactly corresponds 56 plus 36 is 92. But the number of neutrons, 94 plus 139, is 233. And this is 236. So, three neutrons are free. They are just flying away. Now, what happens next? These three neutrons, since they're flying away, they are meeting other uranium-235 nucleus. And each one of them is capable to bring this nucleus into unstable variation and it will break. And it will cause another three neutrons. So, it's a chain reaction. The number of neutrons is increasing and increasing. And that's why the number of nuclei of uranium is also increasing and it's a chain reaction. It's greater and greater and greater number of uranium nuclei are breaking into these components. And every breakage really has a certain amount of gamma radiation and heat, basically, radiation which is released. And that's what we are using to boil the water. Now, why this heat is released? Well, if you will take mass of this plus this plus this, it will be less than mass of this. Where is the rest of the mass? It's converted into radiation. According to, for instance, Einstein's famous formula. This is the mass, this is the total amount of energy and this is the speed of light. So, if there is a deficiency in mass here relative to this, then the rest is converted into energy. That's gamma radiation, it's heat, and that's how we produce the heat to boil the water. And then it goes exactly the same way as before with the coal burning station. Water is boiling, producing steam. Steam hits the turbine. Turbine is rotating and rotation of the turbine is converted by generator into electricity using collector magnetic induction. Well, that's basically it. Now, what's good and what's bad about this? Well, obviously, it's a very powerful thing. We have to be able to control this reaction because if we don't control the number of neutrons released by this reaction, it will go into a chain reaction and it will explode. That's what atomic bomb actually is. So, the whole thing is arranged in such a way that the core, the uranium core, has certain channels through which we put something which slows down the neutrons, which absorbs the neutrons and doesn't let them to heat uranium. This is uranium around it. And these are absorbed like a graphite, for instance, or some other maybe materials. They're used to consume the neutrons. And these rods can go up and down. If they go up, that increases the reaction. And as it slows down, it slows down the reaction. It can actually stop the whole reaction because it will consume practically all neutrons produced by some chain reaction and it will not actually do anything. Now, obviously, somewhere should be the initiation, some kind of a source of neutrons which initiates the whole thing. It's really a complex machinery which is around this. We have to really make it safe. Unfortunately, there were, well, few very, very bad incidents with nuclear reactions. Some of them because of negligence, some of them because certain, like negligence was in Chernobyl, for instance, in Fukushima in Japan that was the hurricane and the water, actually, which hit the whole plant, which was not far from the shore. And it actually damaged all these control mechanisms and something went wrong, basically. So it's kind of dangerous because the whole amount of heat, radiation, and all kinds of waste, it actually is very, very dangerous. So we have to really be very careful with nuclear plants. Now, by the way, these are produced results of nuclear fission. It's called fission, this breakage. And some of the parts, some of the elements which are produced by this fission are not stable themselves and they are probably separated into certain parts as well. So it's much more complex than just this. But this gives you a general picture of what's going on. This is a simplified, obviously, picture. And the result of the whole thing is some elements which we have to do something with. I mean, it's a nuclear waste, basically. So that's another problem which we have to really do something with nuclear waste. After uranium is completely, well, exhausted as far as nuclear, which can really break into parts based on neutrons bombardment. Whatever is left of it is really radioactive and it must be buried somewhere. So that's another problem with nuclear power plants. Well, as you see, nothing is cheap in this world. We are producing something which we need. But the price for this is that we have to do something. And these actions produce sometimes not only positive effect which is energy which we are consuming but also some negative effect towards environment, towards people's health and stuff like this. And dangers, actually. Sometimes it's dangers. Anyway, that was kind of a general lecture about how we produce electricity. Well, in most volume is actually quantities when the power plants are involved. That's basically it for today. The notes for this lecture on Unizor.com and every lecture has notes, actually. So the notes have a couple of nice pictures. For instance, the picture of how nuclear plant is arranged, how this fission happens, it has a picture of hydroelectric plant, et cetera. So I recommend you to look at the notes to this lecture. From Unizor.com you have to pick the physics protein course and the electromagnetism part of the course. And it has a few lectures related to distribution of electricity. This is the first lecture, distribution which is on the power plant side. Next lecture will cover transit from power plant to consumers and the third lecture would be how the consumers are actually getting this electric energy. That's it for today. Thank you very much and good luck.