 Hi, I'm Zor. Welcome to Unisor Education. Today I will have the final lecture about distribution of electricity, distribution to consumers. This is the final stage of distribution. I mean that's the purpose actually, right? Why do we produce electricity to consume it, to do something important for us? Okay, now this lecture is part of the course, Physics for Teens, presented on Unisor.com. I suggest you to watch the lecture from this website because it's part of the course and the website has menu with proper order and there is actually prerequisite course called Mass for Teens on the same Unisor.com, which I believe is the necessary component of your background before you start learning physics. Now this lecture actually the whole chapter is not about mathematics. It's only kind of explanatory kind of things, but most of the physics involves mass to a very, very high degree. Okay, now in the previous lecture I have introduced the concept of a grid as something which all the producers of electricity, like power stations, generators, whatever, if they would like to distribute this electricity to the population of a country, they actually have to adhere to certain standards and be connected to something which we call a grid, right? Remember the grid. The grid allows you to assure that there is an uninterrupted power supply to all the consumers connected to the grid. So it's basically like a parallel connection. All the producers of electricity and are connected parallel and all the consumers are connected basically parallel. So they are assured that there is always something if one particular generator stopped working for whatever reason, there are others which contribute to the grid, the proper amount of energy which is then consumed. And obviously there is certain balance between producing and consuming. The more we consume, the more generators we have to really install, right? Now it might make an impression that there is some kind of a gigantic wire, well actually two wires. All the producers of electricity, all the power stations etc. are connected to it and all the consumers are connected to it. And there is a high voltage on this wire which assures that our losses of electricity, losses of energy on heat are smaller. That's not the case. Much more complex situation. Now obviously when we are transferring electrical energy on a big distance, we do have to have this high voltage. Now our devices which we are using, like electricity or electric motors etc., are not designed for such a high voltage. They are always designed for a lower voltage with higher current. And it means that we have to have transformers. Also generators are not generating the high voltage. We need transformers to bring the voltage up to the level used on a long transmission lines. But now as soon as we have covered this long distance, let's say we have reached a city, we can't really put a transformer in front of every device which consumes the electricity obviously. That's just impractical. And the transformer which transforms a very high voltage. And high voltage means basically hundreds of thousands of volts used along the long transmission lines. So transformer which transforms this high voltage into lower like a couple of hundred volts are big, bulky, expensive. So you can't really attach such a transformer in front of each device obviously. So what do we do? Well we do it in steps basically. Let's do it differently. Let's have this grid which we were talking about before, like a high voltage grid where big power producers are connected to be one thing. And then we will make another grid inside the city which is also a grid basically. And it's connected to one transformer between the high voltage grid used for transmission and lower, not low, but lower voltage which is then distributed in the city. So let's say these are your power producing electric power stations, generators, whatever it is. Now there is a high voltage coming to this. So this is one and this is another. Okay and this is going further. So these are two generators which basically produce electricity and they are connected parallel to each other. And I have to have this little thing like this. They are connected parallel to each other and this is the main transmission wire and it's a long one. Then we have a city. So what I'm suggesting is let's put a transformer here and lower the voltage from whatever the high voltage is in this transmission line into another and then make a grid within the city. Okay that's an idea. Now within the city we have already lower voltage here than there and higher current. But these are smaller distances so we can actually think about what is the most economically viable way, what kind of voltage is the most beneficiary from the cost perspective most likely. And then we can distribute it in the city along the streets. So you have one street, you have another street and you have another street. Now these are going to streets but now we have buildings on the streets. Buildings might have a certain number of apartments or it's a private house, doesn't really matter. Whatever it is we might actually need again lowering the voltage. So what makes sense is the street voltage, let's call it this way, street voltage which is produced here might have in front of the building one particular transformer which transforms street electricity into building electricity voltage which is even lower and that one is already fit for devices. So these are in this particular case it's a three levels. So one level is high voltage then you have a well let's call it city voltage and then we have a building voltage. In any case it doesn't really matter how we call them. What matter is that we are gradually reducing the voltage from the very very high to acceptable level for devices which we are using. And that's basically the general design of real distribution to consumers. It might be more than three levels, in this case it's three, maybe it's four, maybe it's one for like a big region and then within the region there is another little grid. So what my point is that grid is not something which is like everything is interconnected that's not the case. Grid is actually a combination of many grids localized which are connected among themselves to bigger grids or high voltage grids through transformers. So there is no real connection. Transformer is not a connection. Transformer is some kind of a way we transform energy from one grid to another grid and that other grid can have lower or higher energy, lower or higher voltage. So this is energy distribution. So electricity by itself as it is electrons which are produced here are not going there. They are ending their way here and then other electrons are started moving here because of the alternating current will produce alternating magnetic field in the transformer and that induces the electricity in the secondary wire, right? So basically there are not physically connected wires. Electrons are not moving all the way to consumers but we have one grid and then we have another grid and then another grid etc etc. All grids are connected among themselves. Through transformers not physically connected like wires, wires to wire, but transformers through the magnetic field which is basically circulating inside the transformer's core. Now what is important however that within each grid, let's say the big grid or a building grid or anything whatever, all the devices must be in sync with themselves. So in this particular case what's important is that if we are introducing another, well if there are no producers of electricity here, if only consumers are, then we don't have to worry about synchronization or anything else because this transformer for instance is producing one particular frequency, whatever frequency comes in, there is a frequency which comes out, maybe with a shift in the phase but doesn't really matter but everything else is just consuming this electricity. But if we want to put another, let's say lower power or something like this, another generator, for instance a group of buildings can have their own small electric power station and produce electricity only for these buildings but it can produce more which means the rest of the electricity which we're not consuming must actually go back to the grid which means it's supposed to be synchronized because again as you remember from the previous lecture, if we have many different producers of electricity connected to the same wire, the same physical wire, the same grid basically, they have to be of the same voltage, of the same frequency and of the same phase so they don't really work against each other. So let me just give a real example of the voltage for instance. The voltage here might be something like 600 000 volts. The voltage which is converted from one to from this ultra high voltage to let's say called city voltage whatever can be something like 7200 volts. You see it's significantly smaller like almost a thousand, ratio almost a thousand to the less. Then each transformer which is transforming energy here should actually go even lower let's say it's 240 volts which goes to the building and that's distributed through the building and actually it can convert into two or three different voltages with two or three different basically physical wires for instance 120 volts. So for instance in the apartment buildings where I live every apartment has two inputs basically one is 240 volts and another is 120 volts. All the smaller devices like a lamp for instance are connected to 120. If I have a big air conditioner I have a special outlet which has 240 volts in it. So basically that's a general picture. Now let's talk about one more thing. The generators are not really generating this type of a voltage. For instance I've heard that Niagara Falls for instance power station I think it has 13 000 volts producing which means that we have to have here another transformer which actually is raising the voltage. So this transformer is increasing the voltage and decreasing the current. So the small current goes along the long lines and these are decreasing the voltage back to the level acceptable for the street sides and the buildings. So for instance in the city you have wiring along the streets which basically are street wires. In this particular case it's 7200 volts but then in front of the building you have some kind of a transformer. Well in front of my building for instance there is a transformer it looks like a big barrel which transforms for instance 7200 into 240 and 120 into two different ways. And another complication which I did mention but I didn't really exemplify it. Let's say you have decided to put a solar panel on your roof. Well it actually a solar panel produce direct current it's not alternating current but all your devices in your house or your apartment they are usually AC alternating current. So what's the complication? Well number one you have to convert DC into AC direct current into alternating current which is not such a simple thing. Actually alternating to direct is much easier. But anyways there are special devices called inverters which can invert direct current into alternating current. Now you're feeding your lamps your refrigerator from the solar panel okay fine but in many cases solar panels produce excessive electricity which can be returned back to the grid which means they have to be connected to the grid somewhere here this is the building right. So if there is a solar panel here which generates certain electricity converted into alternating for DC and then into AC we have to synchronize it with this grid because these are physically connected things. So at least within the building we have to really do it or if you want to connect it to a street level we have to synchronize it with the street level which means voltage which means frequency and phase. Actually voltage is easy because you just put a transformer. Frequency is also easy it's always constant like in 50 or 60 Hertz there is no problem but to adjust transformer sorry inverter to adjust inverter which is producing the electricity from the DC to AC to adjust it in some way so it's in phase with the electricity which is in the grid that's not an easy thing and it requires certain skills. So that's just small complication let's put it this way. I was trying to make this point in the previous lecture that grid is not something which we have just made and it's there basically and doesn't really require anything. It's a very complicated number of interrelated devices which require constant attention, constant maintenance and it's also not fixed in the way that we are producing. We are manufacturing new generators, new equipment, new power stations are coming into the whole grid so basically there are a lot of things which we have to do all the time so it requires a lot of time, a lot of attention, a lot of money. It's very expensive but the purpose is to make an uninterrupted energy supply to the whole country basically to the economy of the whole country. So what else did we cover? Yeah basically that's it. Yeah I was talking even about solar panels. All right so this lecture basically completes the distributions of electricity, a few lectures and again the grid is the most important component of it. So next couple of lectures will be about usage of electricity and that's basically when it's already reached to the consumer so we'll talk about consumers and the whole basically the whole chapter is not really very mathematical. It's all explanatory kind of things. I would like you to understand that the whole thing has certain structure, it has certain components and what kind of components basically that's the purpose. So that's it for today. Thank you very much. Oh by the way I forgot in the notes for this lecture on unizor.com there are much prettier pictures than this one basically of more or less a model of a grid how it looks like. So I do suggest you to go to the website and look at the notes for this lecture. You have to go through physics 14, electromagnetism and then distribution of electricity. It's one of the lectures in the distribution thing. All right that's it. Thank you very much and good luck.