1 00:00:00,012 --> 00:00:05,948 Today we're going to be continuing on our energy conversion. 2 00:00:05,948 --> 00:00:13,538 And we're going to dive a little deeper into the first law of energy conversion 3 00:00:13,538 --> 00:00:18,232 that I covered very briefly in the last lecture. 4 00:00:18,232 --> 00:00:23,767 And show some examples and try to get a little better understanding of what we're 5 00:00:23,767 --> 00:00:29,083 talking about and what the, what the limitations do to us regarding the first 6 00:00:29,083 --> 00:00:33,398 law of energy conversion. That say's you cannot create or destroy 7 00:00:33,398 --> 00:00:36,666 energy. and we're dealing with the middle box 8 00:00:36,666 --> 00:00:41,884 here, where we're, converting energy from one form that we find in it's natural 9 00:00:41,884 --> 00:00:47,353 state, to the form that society Needs and wants they're willing to pay for. 10 00:00:47,353 --> 00:00:53,130 We've already been over this diagram, looking at all the infrastructure that we 11 00:00:53,130 --> 00:00:56,863 have in order to carry out this conversion process. 12 00:00:56,863 --> 00:01:02,715 And repeating the 1st law, total energy cannot be created or destroyed, it is the 13 00:01:02,715 --> 00:01:08,643 1st law and That, that sometimes comes a little surprising, because a lot of times 14 00:01:08,643 --> 00:01:14,070 in the press, and the media, and the public, we talk about producing energy. 15 00:01:14,070 --> 00:01:20,362 but when we produce energy, we're always using energy on the other side somewhere. 16 00:01:20,362 --> 00:01:25,297 There's got to be an energy input before we can produce it from our hot air 17 00:01:25,297 --> 00:01:30,637 furnace or from our, with our automobile or for our wind turbine or something. 18 00:01:30,637 --> 00:01:34,813 There's got to be an energy source in order to produce energy. 19 00:01:34,813 --> 00:01:39,875 So we're not, we're never creating energy, we're only converting it again 20 00:01:39,875 --> 00:01:43,712 from one form to the other. So I can't say that enough. 21 00:01:43,712 --> 00:01:49,278 Now there, to dive a little deeper we need to understand what types and forms 22 00:01:49,278 --> 00:01:54,926 of energy we're talking about here. What all, are some of the different forms 23 00:01:54,926 --> 00:02:00,157 that we typically deal with. Well work is one of the, one of the most 24 00:02:00,157 --> 00:02:06,437 valuable forms that we have and that is, as an example, is a turning shaft that 25 00:02:06,437 --> 00:02:12,197 turns the axle to our car with a torque on it that drives our car or when we 26 00:02:12,197 --> 00:02:18,717 pedal our bicycle, we're turning a shaft that powers the rear wheel that pushes us 27 00:02:18,717 --> 00:02:25,426 up a hill or against the wind resistance as we ride our bicycle electricity is 28 00:02:25,426 --> 00:02:29,988 another form of energy. And there of course, that's a current and 29 00:02:29,988 --> 00:02:34,862 voltage that's carried over a wire. Electricity is a very nice form of 30 00:02:34,862 --> 00:02:38,285 energy. Because it's one that can be transported 31 00:02:38,285 --> 00:02:43,322 over long distances very efficiently. Work, you got to have a shaft. 32 00:02:43,322 --> 00:02:46,917 And to carry that work from one place to another. 33 00:02:46,917 --> 00:02:52,787 Of course, you don't want to have a mile off shaft to carry work from one place to 34 00:02:52,787 --> 00:02:56,249 another. But we can produce electricity at one 35 00:02:56,249 --> 00:02:59,678 place and carry it over a mile long power line. 36 00:02:59,678 --> 00:03:04,012 And then use it to power an electric motor on the other end. 37 00:03:04,012 --> 00:03:08,582 And that can produce our work. So electricity is one that. 38 00:03:08,582 --> 00:03:14,464 That is a very nice form of energy. But, of course, we don't find it in a 39 00:03:14,464 --> 00:03:18,654 natural state. We always have to generate it from some 40 00:03:18,654 --> 00:03:22,098 other source. Kinetic energy is one that we're 41 00:03:22,098 --> 00:03:27,862 probably, fairly familiar with in, that regarding a moving car. 42 00:03:27,862 --> 00:03:34,104 you have to put energy into the car from when you're at a stop light in order to 43 00:03:34,104 --> 00:03:39,314 accelerate it to 25 mph to get to the next stop light in, in traffic. 44 00:03:39,314 --> 00:03:45,618 so it has kinetic energy and then if, unless you're dealing with a hybrid car, 45 00:03:45,618 --> 00:03:51,511 you put your brakes on which produces friction and turns that kinetic energy 46 00:03:51,511 --> 00:03:55,193 into heat. That heats up the breaks and dissipate 47 00:03:55,193 --> 00:04:00,457 that energy, that kinetic energy. Dissipate it into thermal energy or into 48 00:04:00,457 --> 00:04:03,618 the atmosphere. So it's wasted, so to speak. 49 00:04:03,618 --> 00:04:09,085 we put it into the card to create the kinetic energy but then we don't get it 50 00:04:09,085 --> 00:04:12,412 back out. The hybrid car uses a generator to. 51 00:04:12,412 --> 00:04:17,594 link into the brakes, and the braking is done with a generator that generates 52 00:04:17,594 --> 00:04:22,488 electricity then and stores it in the battery to accelerate when we get ready 53 00:04:22,488 --> 00:04:28,275 to start back up, from the stop light. thermal energy is and, and that's 54 00:04:28,275 --> 00:04:33,235 sometimes we call heat. This one that a warm cup of coffee is 55 00:04:33,235 --> 00:04:37,496 contains thermal energy. Any kind of, of object that has a 56 00:04:37,496 --> 00:04:43,466 temperature above ambient temperature. Whatever the ambient atmospheric 57 00:04:43,466 --> 00:04:49,121 temperature is at that point in time. If you have any substance at a 58 00:04:49,121 --> 00:04:55,423 temperature higher than that, that's what we call thermal energy or heat. 59 00:04:55,423 --> 00:04:59,058 Hot air, hot coffee, or warm house inside. 60 00:04:59,058 --> 00:05:04,663 All that's thermal energy. And it's another form of energy that we 61 00:05:04,663 --> 00:05:09,270 want and like. Hot water to shower with is another place 62 00:05:09,270 --> 00:05:14,057 where we have thermal energy or heat, as sometimes we call it. 63 00:05:14,057 --> 00:05:20,709 chemical energy is one that's in the, the chemical make up with our, our electrons 64 00:05:20,709 --> 00:05:27,641 bonded to the other molecules into the nucleus of our atoms and molecules and, 65 00:05:27,641 --> 00:05:34,136 we can carry out a chemical reaction and release that, chemical energy, or we can 66 00:05:34,136 --> 00:05:39,803 create more chemical energy by putting energy into it driving the chemical 67 00:05:39,803 --> 00:05:45,106 reaction to increase the chemical energy. So gasoline is 1 that is an example 68 00:05:45,106 --> 00:05:48,103 there. Gasoline has chemical energy in it. 69 00:05:48,103 --> 00:05:53,354 And we carry out a chemical reaction of that gasoline with oxygen in the air. 70 00:05:53,354 --> 00:05:59,289 As we saw the formula when we Talking about oil and, that releases, that 71 00:05:59,289 --> 00:06:05,107 chemical energy as thermal energy, or heat and can, and produces a very high 72 00:06:05,107 --> 00:06:11,222 temperature flame, that when can use to heat homes or to heat hot water or Drive 73 00:06:11,222 --> 00:06:14,980 a power plant. Radiation is the final example that I 74 00:06:14,980 --> 00:06:20,726 give you and that's of course the best example is the sun's rays that, radiation 75 00:06:20,726 --> 00:06:26,603 coming from the sun is radiation energy. You also feel it in front of a fireplace, 76 00:06:26,603 --> 00:06:31,202 if you have a. Wood burning fireplace then, and you have 77 00:06:31,202 --> 00:06:35,851 a lot of hot coals. Those coals radiate that, and that's 78 00:06:35,851 --> 00:06:40,995 thermal radiation we call it. But the sun rays of course, that 79 00:06:40,995 --> 00:06:47,267 radiation is 1 that we use in solar energy to produce electricity or produce 80 00:06:47,267 --> 00:06:53,382 hot water to heat our pools and. The things, so those are just some of the 81 00:06:53,382 --> 00:06:59,357 forms of energy and we can convert these forms from one to the other, as is shown 82 00:06:59,357 --> 00:07:02,862 here. So we put energy into some kind of energy 83 00:07:02,862 --> 00:07:07,752 conversion system that would design to take that form of energy. 84 00:07:07,752 --> 00:07:14,450 Work, electricity, heat, chemical energy kinetic energy, potential energy, etc., 85 00:07:14,450 --> 00:07:20,240 and, and convert it to some other form of work, eletric, that is one of the work, 86 00:07:20,240 --> 00:07:24,428 electricity, heat, chemical, kinetic, potential, etc. 87 00:07:24,428 --> 00:07:30,261 for instance, you can take you can take work, and put it into a generator, 88 00:07:30,261 --> 00:07:34,777 electric generator and electricity comes out of the generator. 89 00:07:34,777 --> 00:07:38,382 So that's one of the energy conversion processes. 90 00:07:38,382 --> 00:07:42,653 That we do a lot in, to produce electricity. 91 00:07:42,653 --> 00:07:50,751 we might put heat in by burning coal in a power plant, and dry, and boil steam and 92 00:07:50,751 --> 00:07:57,574 go through a cycle that produces electricity also kinetic energy is I 93 00:07:57,574 --> 00:08:02,332 already mentioned, an automobile is one of the best examples of that. 94 00:08:02,332 --> 00:08:08,001 Potential energy, if the automobile is high on a mountain then it has potential 95 00:08:08,001 --> 00:08:11,392 energy. As it, and gives up that potential energy 96 00:08:11,392 --> 00:08:17,144 as it comes down the mountain or comes down the hill and you can Easily convert 97 00:08:17,144 --> 00:08:22,156 kinetic energy from the dropping potential energy as you coast down the 98 00:08:22,156 --> 00:08:26,626 hill with a bicycle or a car. So we got potential energy coming in on 99 00:08:26,626 --> 00:08:32,030 the left hand side and kinetic energy as a vehicle, or bicycles speeds up as you 100 00:08:32,030 --> 00:08:35,787 come down the hills. So all of these, these are energy 101 00:08:35,787 --> 00:08:40,093 conversion processes. Some of them are more complicated than 102 00:08:40,093 --> 00:08:43,048 others. Some of them are more difficult to 103 00:08:43,048 --> 00:08:47,145 execute than others. But they're very important to use the 104 00:08:47,145 --> 00:08:50,696 energy forms that we find available to us on Earth. 105 00:08:50,696 --> 00:08:54,265 To. produce the forms of energy that we want 106 00:08:54,265 --> 00:09:00,903 in order to make life more comfortable. taking an example, and I mentioned the 107 00:09:00,903 --> 00:09:06,647 bicycle coasting down a hill, That converts the potential energy to kinetic 108 00:09:06,647 --> 00:09:11,437 energy and I just put some numbers on here to show, you don't need to know how 109 00:09:11,437 --> 00:09:15,687 to make the calculations. Some of you probably do but just as an 110 00:09:15,687 --> 00:09:20,527 example, if you have a 10 ft high hill and you coast, coast down a hill this 10 111 00:09:20,527 --> 00:09:26,349 ft high and you have no wind drag or wheel friction, varying friction and 112 00:09:26,349 --> 00:09:29,645 rolling friction of the tire on the surface. 113 00:09:29,645 --> 00:09:35,357 Then you could, the vehicle, the bicycle would accelerate 17 miles per hour. 114 00:09:35,357 --> 00:09:39,467 And that would be true for a car as well as for a bicycle. 115 00:09:39,467 --> 00:09:45,661 It would be, it's irrelevant of the mass. in the metric system, if it's a 3 meter 116 00:09:45,661 --> 00:09:51,621 high hill And you coast down it, you'll can ideally create 28 kilometer per hour 117 00:09:51,621 --> 00:09:55,160 speed. but that's the ideal, that's the upper 118 00:09:55,160 --> 00:09:58,358 limit. If somebody comes to me and says he can 119 00:09:58,358 --> 00:10:03,943 do better than that, then I am very skeptical about something because, it, 120 00:10:03,943 --> 00:10:08,502 it's, it someway energy is being created from something else. 121 00:10:08,502 --> 00:10:14,037 Are created from nothing, so this is the upper limit if we have a friction-less 122 00:10:14,037 --> 00:10:19,759 process, ideal friction-less process with no wind drag and no rolling friction. 123 00:10:19,759 --> 00:10:25,348 but total energy is not created. Energy is merely converted from potential 124 00:10:25,348 --> 00:10:30,696 energy to kinetic in this, so this a, a good practical example, one that you 125 00:10:30,696 --> 00:10:37,063 could probably intuitively understand. But of course, we do the opposite when 126 00:10:37,063 --> 00:10:42,646 we, when we climb back up the hill. We're adding potential energy to 127 00:10:42,646 --> 00:10:47,162 ourselves and to the bicycle so that we can coast down. 128 00:10:47,162 --> 00:10:52,021 On the other side. Another example is we take natural gas 129 00:10:52,021 --> 00:10:56,905 chemical energy and we burn it with the oxygen in the air. 130 00:10:56,905 --> 00:11:03,635 Furnace is shown on the right hand side, that's a typical warm air furnace as we 131 00:11:03,635 --> 00:11:08,300 call it in the US. The European Western European and in 132 00:11:08,300 --> 00:11:12,222 other countries. Don't have as many of the warm air 133 00:11:12,222 --> 00:11:18,007 furnaces, they have more water radiators. But this one burns natural gas and 134 00:11:18,007 --> 00:11:23,397 releases a chemical energy into a flame and that warm thermal energy is then 135 00:11:23,397 --> 00:11:29,237 transferred to the air that's circulated from the house and fed, then blown with a 136 00:11:29,237 --> 00:11:33,797 fan back into the house. So warm air heat is added back to the air 137 00:11:33,797 --> 00:11:38,502 in the house. from the chemical start what, the energy 138 00:11:38,502 --> 00:11:42,917 that started off as chemical energy in the natural gas. 139 00:11:42,917 --> 00:11:47,677 So, the gas furnace is a nice energy conversion device. 140 00:11:47,677 --> 00:11:52,132 Converting chemical energy to chemical energy or heat. 141 00:11:52,132 --> 00:11:58,066 [SOUND] so those are some examples and trying to get a little better handle on 142 00:11:58,066 --> 00:12:01,738 what we mean when we talk about energy is conserved. 143 00:12:01,738 --> 00:12:07,252 Total energy conserved not kinetic energy is conserved or potential energy is 144 00:12:07,252 --> 00:12:10,350 conserved or chemical energy is conserved. 145 00:12:10,350 --> 00:12:15,490 But total energy of all of the those added together of the Earth are in our 146 00:12:15,490 --> 00:12:20,687 box that we're dealing with. you can't, can have more energy coming 147 00:12:20,687 --> 00:12:23,587 out than you have going in. Okay, thank you. 148 00:12:23,587 --> 00:12:28,162 Next time we'll deal with the second law in a little bit more detail. 149 00:12:28,162 --> 00:12:28,800 Thank you.