 Hi, I'm Zor. Welcome to Inezor Education. Today we will talk about how electricity is going from the source where it's produced, generated, like a power plant, to consumers. Manufacturing, lighting on the streets, apartment buildings, houses, etc. So, this is the transit, basically, how this transfer of energy is arranged. Well, we don't have any other way to transfer electricity but through the wires. So, basically it's about wires, this lecture. Okay, now this lecture is part of the course called Physics 14 presented on Unizor.com. I do suggest you to watch this lecture and all others actually from the website because the website basically has a course, which means there is a menu, there is a certain sequence, there is order of lectures. All the lectures have very detailed notes like a textbook, basically. So, you have a live presentation and you have the text with basically the same information. Also, the website has exams for certain topics. Everything is completely free, there are no ads, no advertisement, so no financial strings attached. You don't have to put any information about yourself. If you sign in, it will give you an opportunity to save the history of your exams. If you don't sign in, you can just do it without signing in, no problem. Alright, so, back to business. We are talking about delivery of electricity to consumers through the wires. So, basically we can imagine that we have some kind of a power plant, which usually generates alternating current. And we have some kind of a consumer, let's say it's an electric motor which pumps up the water up to the roof of the building, so people have water in their apartments, just for example. Which means it should actually work on a 24x7 basis all the time. And we have obviously wires, so we have two wires, a pair of wires. Which goes to and back, or considering this is alternating current, it goes to and back the other way. And it's alternating like 50 or 60 times per second. Alright, great. For a small scale, it works without any problems. Now, let's talk about the reality. In reality, this is a power plant and this is, let's say, a building in the city, which is definitely far away. It can be hundreds of kilometers away from the power plant. So, these wires are pretty long. Now, obviously everything has electric resistance. There is an electric resistance inside the wiring in the generator. There is obviously electric resistance in the wiring of the motor and the resistance of the wires. Now, the resistance is basically, it's not good. I mean, this is what produces the waste of electricity. It's converted into heat. And, you know, the main formula for producing heat by electric current is basically something like this, times t. And if you're talking about unit of time, so per second, let's say, this is what happens every second. We are wasting that much of energy to heat, which we don't really need here. We need energy to rotate the motor. Heat is waste. So, we have to think about how much we are actually wasting and maybe minimize it somehow. Well, the construction of generators and the construction of motors are pretty fixed actually, not too much. I mean, we have to put more wires to get more energy basically, right? Nothing we can do about this. Now, speaking about this wiring, again, length is fixed basically. Now, what is the resistance of the wire as it relates to the length? Well, it should be proportional, right? Twice as long would be twice as resistive. Now, it's also inversely proportional to area of the cross-section of the wire, the thicker the wire. The more room electrons have to go through, right? So, the area of the cross-section is very important, the greater the area, the less resistance. So, basically, it's like this. Raw is basically a characteristic of material the wire is made of, let's say. Copper has different coefficient raw than, let's say, aluminum. L is a length and A is area. All right. Now, so we know this, we know R in this formula. Now, what is I? Well, let's just think about a very simple thing. The motor in the building where I live, I just know it has a power of about 2.2. It has a 2 actually, they say 2, but I'm using 2.2, it will be easier to divide by 220 volts. So, this is kilowatt. And the voltage is 220 volts. Now, obviously, power is equal to voltage times amperage from which amperage is equal to P divided by U, which is 2,200 volts divided by 220, it's 10 ampere. And this is kind of a normal thing. For a good powerful motor, 10 amperes is practical. All right, fine. So, we have numbers. So, let's just calculate how much energy we are wasting for, let's say, L is equal to... Well, let's just have 1 kilometer, which is really very, very close to a power plant. 1 kilometer. 1000 meters. So, what do we have here? I is 10, so I squared is 100 times R. Now, R is... Now, we need rho. Rho is 1.7 times 10 to the minus 8. Rho is 1.4 meters. Okay. Times L, L is 1000 meters. So, it's 1.710 minus 8, it will be 1.710 minus 5. And divided by A area. Okay, so let's have, for instance, diameter of the wire is 2 millimeters. Again, quite practical. 2 millimeters. Now, with 2 millimeters, I have the area, therefore, it's pi G squared divided by 4. So, this is 2 millimeters. Millimeters is 10 to the minus 3rd meter, right? So, 2 squared is 4 divided by 4, 1, so we have 10. But it's a square, so it's 10 minus 6. So, it's 3.14 times 10 minus 6. Okay, we divide it. Right? So, minus 5 minus 6 goes there, so it's 17 divided by 3.14. Well, it's about 5, more or less. 5.4. Okay, 5.4 ohm. That's the resistance of the wire. By the way, there are 2 wires here. I said 1 kilometer, that's the total length, which means it's like 500 meters apart, basically. Very close. And even in this case, let's just calculate how much energy we are wasting. So, R is 5.4, I squared is 100. So, we have 540 watts. Well, approximately half a kilowatt. We are wasting every second. Well, let's multiply it by, so, 0.5 kilowatt, a little more. Times 3,600 seconds in the hour. So, that's what it's half. So, it's 1,800 kilowatt. Right? And times 24 hours per hour. So, that's an hour. Right? That's per hour. And multiplied by 24 hours, we have... What do we have? I think I have these calculations. Something like 4 to 3,000, something like this, right? 1,000, yes, 4 to 3,000 approximately. Kilowatt hours. Now, if you take, for instance, the price, let's say, 10 cents, 1,200 cents per kilowatt hour, whatever. 10 cents, let's say 10 cents. So, it's about 10 of a dollar. So, we have 430 dollars every day. So, to feed this motor, we have to spend almost like half a thousand dollars every day. That's expensive. And we have to really reduce this cost somehow. Now, as I was saying, the reducing wiring here or there is really counterproductive. Because if we are reducing the number of wires here, we will have less power produced. If we will have less wiring here, it will be less power consumed. So, this is kind of fixed. And it's defined by the functionality. We need certain power to pump the water. And we need certain power here to generate this energy. So, how can we reduce the amount of energy which we spend here? Well, let's just go back to this formula. It's either reducing R or reducing I. Reducing R and R depends on, as we know, on two factors basically. This length is fixed. I mean, we have to cover the length, right? So, this is, rho is the quality of the material. Well, copper is one of the best in this particular case. Maybe aluminum. They have a very low resistance. Well, silver has even less. But that would be very expensive to have silver wiring. So, increasing area, well, that's a possibility. But let's just think about how can we increase the area. We can make a thicker wire. There are some practical limitations to the thickness of the wire. I mean, we can use many wires, actually, and put it in a cable parallel to each other. Yes, we can. But, again, it will be heavy. We have to put it somewhere, we have to install it. That's very, very difficult. On such a length, I mean, the length can be, instead of, you know, 500 meters, it can be 500 kilometers. So, not practical. What is practical is reducing I. Here comes transformers. What does the transformer do? Let's just go back to something which we were discussing before. The transformer has two solenoids. One with, let's say, a smaller number of loops. Another with a bigger number of loops. So, this is source of electricity, which is producing certain voltage and amperage. In this circuit. Then this will be induced current. Why it will be induced? Because it's an alternating current. And alternating current creates alternating magnetic field. And alternating magnetic field creates an alternating current. Right? The U here, this is U1, I1, U2, I2. The power should be the same. Because there is no, there is a law of conservation of energy, right? Voltage times amperage is the power produced. So, it's amount of energy per unit of time. So, this is the same. Now, if number of loops here greater, then correspondingly proportionally U2 will be greater than U1. And, therefore, I2 will be proportionally less than I1 by the same factor. So, if I will increase the voltage by factor of 10, my amperage will be reduced by factor of 10. I mean, obviously, there are some losses again, waste exists everywhere. But, approximately, we can just consider this is. So, this is the way how we can reduce I by increasing the voltage. So, what we do is we put transformer here. And instead of direct connection, we will have one solenoid. And this is much greater number of loops. And we will do the same here. We'll put another transformer with big number of loops and smaller number here. So, what will happen? Immediately before going into the wire, this direction or this direction doesn't really matter. We will increase the voltage. And immediately after, we will decrease the voltage. But the voltage between these two will be very, very high. Well, how high it depends, obviously. But let me tell you, the voltage which is produced by the generator is not really very high. I mean, obviously, it depends on, again, number of loops of the wires inside the generator, etc. But it's not very high. This voltage, which is used to transmit energy to a very, very long distance, can be very high. And it basically depends on us. Now, in real life, the voltage in the long lines can be, I think, 1000 volts is one of the lowest transmitting voltages. On the higher end, when we are transmitting the energy to a very, very, very long distance, it can be up to 800,000 volts or even larger. It's called ultra-high voltage lines. So, obviously, they should be properly insulated, etc., etc. But what's important is that we have electricity transmitted between these two, between the consumer and the source. We have this voltage very, very high. And now, again, by reducing the amperage by the factor of 10, we are reducing the waste of energy by the factor of 10 square, which is 100, which is great. And we definitely can have this increase of the voltage much more than 10 times. We are increasing maybe by 100 times, and that would be 10,000 smaller waste. That's the key to transmitting electricity to a very long distance. What's very important, by the way, is to have alternating current, because only with alternating currents we can have the transformers. Direct current doesn't work this way. There is no variable magnetic field. There was a very interesting movie, actually, DC AC or something like this. It's called, between these two technologies, one technology, which was basically pushed by Tesla, which is alternating current. And Edison was pushing the direct current, Tesla 1. Smart guy. So, basically, it's alternating current, and it's a very, very high voltage, and that's how we transmit energy. Now, what's other thing is very important is we need some reliability. We need energy to be constantly available for us. So, if I have just this direct connection between energy producer and energy consumer, even if there are many energy consumers here, we can really connect something else here, right? Reliability depends on this generator. If it goes out of business, we lose electricity everywhere. We need this reliability, and for this, we are arranging a network of energy producers connected to each other, and they're basically like ensuring that there is always energy in the grid. So, it's called the grid, and I'll talk about this in the next lecture, how it's arranged, but basically, all the energy producers are connected and they're contributing to the common energy supply. So, every consumer can have the energy, electric energy from somewhere they don't even know actually where it came from, because it's a grid, something maybe came from the nearest source, but if nearest source is not working, then it will be actually pumped from another source, and it's all automatically rearranged somehow. So, the grid is very, very important, and that actually gives you the reliability of energy supply, and that will be the subject of the next lecture. All right, that's it for today. Thank you very much. I suggest you to go to the website, Unizor.com, read the text for this lecture, and basically that's it. Good luck.