Skip to main content
Loading Explore guides…
Electricity Misconceptions · Acedra
Home
Explore
Physics
Electricity Misconceptions
Sign in to save
Chat
If YouTube asks you to sign in, open the video on YouTube.
Watch on YouTube
Reload player
Transcript
43 segments
Copy
Hide video
0:00
- Hello, my name is Kathy Joseph and welcome to my video where I preview the next 12 videos, I'm planning on making. Ready? Let's go. ♪ Electricity, electricity ♪ ♪ Electricity, electricity ♪ Now I'm planning three videos with a bonus video on three different subjects. That's how I got to 12 videos. It just turned out that way. Part one, understanding current better. So, these three videos and a bonus video, you see why I call it a bonus video in a second,
0:36
are all sort of a response to this video by this man named Derek Muller whose channel is called Veritasium. See, about a year ago, Derek Muller made this video called, "Misconceptions About Electricity." And in this video he said that he thought that the energy of electricity doesn't flow in the wire, it flows outside the wire, which is a statement that many, many people, including me, disagreed with. But his questions, the reasons why he came up with this
1:16
were really profound and really good I thought. The first one was, well if the energy is in the current, then how does it jump from one coil to the other in a transformer? - For one thing, the there is no continuous conducting wire that runs all the way from a power station to your house. No, there are physical gaps. There are breaks in the line, like in transformers where one coil of wire is wrapped on one side, a different coil of wire is wrapped on the other side.
1:45
So, electrons cannot possibly flow from one to the other. - And the second thing was, if the energy is in the current and alternating current goes back and forth, how does the energy go from the power station to our home? - Plus, I mean if it's the electrons that are carrying the energy from the power station to your device, then when those same electrons flow back to the power station, why are they not also carrying energy back from your house to the power station?
2:15
I mean, if the flow of current is two ways, then why does energy only flow in one direction? - And the third part was in DC current, how does the signal go almost at the speed of light, whereas the electrons are drifting at like 0.1 millimeter per second.
2:36
- [Derek] Let's say we have a simple circuit with a battery and a bulb operating at steady state. If you zoom in on the light bulb filament you'd see a lattice of positively charged cores of atoms; the nucleus and lowest shells of electrons, surrounded by a sea of negative electrons which are free to move around the lattice. The actual speed of these electrons is very fast, around a million meters per second but all in random directions. The average drift velocity of an electron
3:03
is less than 0.1 millimeters per second. Now, frequently an electron will bump into a metal ion and transfer some or all of its kinetic energy to the lattice. The electron slows down and the metal lattice starts wiggling more. It heats up and ultimately this is what causes the filament to glow and emit light. So, a lot of people will look at this and conclude the electron carried the energy from the battery to the bulb where it dissipated its kinetic energy as heat. But consider
3:35
where did the electron get its kinetic energy from, before the collision? It didn't carry that energy from the battery. In fact, if the circuit has only been on for a short time that electron hasn't been anywhere near the battery. - So, that is why I ended up with three video responses to this. The first one is about the transformer. And the short answer to his problem with the transformer is that the energy of it is not just in the current, it's in the current times the voltage.
4:06
Actually, that's the power. Power is current times voltage, but the power is the change in energy over time. So, the energy also depends on the current times the voltage. And if you have a changing current and a coil, it induces a voltage in a second coil and that voltage creates its own alternating current, which transmits through the rest of the wires and into your home. So, that's how the energy is in the wires but still jumps from one wire to the next. But it also brings up another issue,
4:45
which is how do step up transformers get more voltage and less current at the same time. As we are often taught that voltage is like water pressure and current is like water flow. How do you get more water pressure and get less water flow? And the answer is voltage is not water pressure. It's an analogy and it's a pretty bad one. And so we need better analogies and better understandings of what voltage is and what current is. And for my mind, the easiest way to understand voltage
5:23
is understand how we measure voltage, which is by how much shock it gives us. Well, that was originally how we measured it. So, what did people do with Volta's battery, before the invention of the LED light bulb? Well, they could give them so shocks. If you wet your hands, you could even feel a shock through your whole body.
5:43
And still how you measure today if you have a nine-volt battery, you can lick it and you can get a little shock, then you know it's still live. That's how we know the voltage and the current is the flow of electrons but they measured it by how much magnetic force it had on a magnetic needle in a compass. So, the way step up transformers work is the more coils you have, the more shocking voltage you get. But due to something called self-inductance, the less current you get.
6:15
And physicists use a different equation for this than engineers do. And I wanna go over all of that in the video. So, that's gonna be my first video which is like about 80% done. So, I'm hoping that will be out in about a week. But if you know me, I tend to be an optimist. So well, I will get it done when I get it done but that will be exciting. And then the next video is answering his second question which is, if alternating current goes back and forth,
6:45
how does energy transfer from one point to another? And my answer is, it's analogous to the motion of sound. Like when I speak, I move air molecules and those air molecules bump into other air molecules that bump into other air molecules that eventually go to my microphone. But the air molecules just go back and forth. They don't travel from my mouth to the microphone. And it's very similar with alternating current. It doesn't go from one place to the other, they just vibrate back and forth.
7:18
But the energy goes from one place to another and with alternating current generators, it goes on both wires at the same time. And I'll go into the little bit, about the history of generators and three phase and the like. And that brings me to my third video, which is on how direct current travels and direct current moves very differently than most people think. For example, it moves in the entire wire. It does not happen on the surface. There's no extra charges on the surface.
7:53
And then I'm gonna discuss how if you have an open circuit, the extra charges collect on the edges, like with the parallel plate capacitor. And then if you have a closed circuit, you have no excess charges anywhere, but you do have a flow of charges drifting. And like Derek's image, tons of electrons are in the wire and each push or pull their neighbors. So, though I agree with Derek that the electrons are moving, because of an electric field, I don't agree with him
8:28
that the electric field is outside the wire. As Maxwell wrote in his equations that the electric field in the wire is related to the current density in the wire by the conductivity of the wire. And that leads me to my bonus video. And the reason it's called a bonus video is it's not very deep, it's just that I've been watching this show, called "Schmigadoon!", which I adore. And there was a song in it where they're trying to encourage this girl to talk to her father
9:01
and they tell this story about a girl who keeps on ignoring her father, and she gets a letter that her father is dead and the thing goes, dead dead dead dead dead dead. ♪ Got one last letter and the letter said ♪ ♪ We're sorry to inform you that your father's dead ♪ ♪ Dead, dead, dead, dead, dead, dead dead, dead, dead ♪ ♪ So talk to daddy, talk, talk to daddy ♪ And I'd said how funny it would be if I said how do you know nine-volt battery is dead
9:32
and then played dead, dead, dead, dead, dead, dead. And my son looks up and goes, "Give me power, give, give me power." And I ended up writing a whole physics song, about electrical power and it has accurate physics and it hopefully will teach you a lot about physics and be useful for teaching physics. But it also fits the song and it rhymes or it, what do they call it? Imperfectly rhymes. - Imperfect rhymes. - Yeah, you know like when you rhyme time with fine.
10:08
- Oh, well come on, that doesn't really matter. - It matters a lot. - I'm probably gonna sing it with someone who can actually sing. So, it's not that painful. That brings me to my next set of videos, part two, three videos and a bonus video on Maxwell's equations. Okay, so I've made a lot of videos on Maxwell's equations, but in that process, I've realized some very important truths. The first thing is that Maxwell made a very big mistake when he wrote his equations
10:40
and it ended up confusing everyone. See, Maxwell wrote his first set of equations in 1856
10:49
and in that paper he didn't do the four Maxwell's equations. He sort of did one and a half of them. He came up with the equation for electric potential and electric field and he came up with the equation for Gauss's Law and he came up with Ampere's Law, but he didn't add Maxwell's edition and he didn't add Faraday's Law. So, in his next paper, he actually started with Ampere's Law, and then he just added that derivative of D to the equation, Maxwell's edition.
11:28
And that's where he made what I think is his big mistake, which is that he said the thing he called the displacement field was a displacement and the derivative of that was a type of current. But in the previous paper, he had the same variables, meaning something completely different. And he didn't change Gauss's Law, he just changed the meaning of Gauss's Law. And I think if you go back to his original meaning for Gauss's Law, all of Maxwell's equations are so much easier to understand.
12:04
So, I'm really excited about this video. So, the first video is gonna be Maxwell's big mistake. The next one's gonna be about Maxwell's biggest success which is not what you might think. Maxwell's biggest success in my mind is actually what's called the vector potential A. Now, when I learned about the vector potential A, I thought it was the stupidest thing I've ever heard and I'm not alone in this. Oliver Heaviside said it was like evil and he wanted to murder the whole body. And most people,
12:36
he really hated it. And most people have ignored it ever since Heaviside, but it's actually profound and wonderful and interesting and I'm really excited about that one too. And then that leads me finally to Oliver Heaviside and the development of Maxwell's four equations. Now, this is an interesting one, because I'm going to talk a lot, about how Oliver Heaviside is famous for doing things he totally didn't do but it's not a takedown of Heaviside. In fact, the more I learn about Maxwell's laws,
13:10
the more I read him and his book, the more I learn about quaternions, the more I learn about all of this, the more impressed I am with Oliver Heaviside. And it's sort of by saying, "Oh, Oliver Heaviside creative vector analysis "and all you need is vectors." And then suddenly Maxwell's equations are four equations, that's denigrating both Maxwell and Heaviside. Heaviside was so much more important than that but also on the surface he did a lot less than that, because it was just so complicated,
13:49
that he was the only one who got anywhere near understanding it, if that makes any sense. All those brilliant people at the time and one guy with the basically a high school education who never took calculus or even trigonometry, taught himself quaternions, taught himself calculus, figured this stuff out. After Heinrich Hertz discovered radio waves to validate the Faraday Maxwell equations. So like once Hertz did that, everyone's like, "Okay," let's read Maxwell. And they opened up his book
14:26
and they said, "Let's not read Maxwell. "This is way too hard. "Let's read Oliver Heaviside." And so that's how it developed. Oliver Heaviside did not write the four equations. He wrote two equations. That's why he called it the Duplex Equations. But he was super influential. And one of the weird ways he's influential is my bonus feature, which is he was influential for creating SI units,
14:55
the units we use, not meters, not seconds and not kilograms, but adding amps to that. That was because of an argument Heaviside made which influenced another person to push for that and that's how we ended up with SI units. So, it's a fascinating story. So, my bonus feature is going to be the history of SI units. And I'm really excited about this, because many years ago I read in the "Short History of Nearly Everything" by Bill Bryson a little bit I think it was in that book,
15:30
about the history of measuring the meter and the second and the kilogram. And it was a fascinating story and I really wanna dig into that more, find out more about it and then add on a bit more about like how they added on amps and why we have these different units. So, I think that's gonna be really cool. And that leads me to my third set of videos, part three, the evolution of relativity in E equals MC square. Now, when I talk about how Oliver Heaviside was really influential
16:03
but didn't actually make the four equations of Maxwell, I end up talking about how Lorentz, ended up making the four equations of Maxwell and he did it to create relativity. And so that leads me directly to how relativity evolved from Lorentz's relativity,
16:27
which was created to explain a way in an experiment that was done the Michelson-Morley Interference experiment, I think I said that right, where they're trying to prove the existence of an aether which goes all the way back to Maxwell doing that strange displacement current thing. Anyway, Maxwell did the strange displacement current, made everyone think that you had to have an aether. So they did this Michelson-Morley Interference experiment to try to prove that there was an aether
17:03
and it didn't work to prove that there was an ether. So then Lorentz made these equations to explain why that experiment didn't work. And so that's gonna be the first video and then the next video is gonna be on how Einstein was like, "Oh, isn't this funny? "You can also say, 'Hey, if we just make the speed of light, 'the maximum speed that you can go at 'and only light can go at the speed of light, 'then you get the same equations that Lorenz get 'and isn't that amusing and seductive?'"
17:36
If you combine that result with Maxwell's equations again you get how energy is related to mass. And so how E equals MC squared evolved. And then the third video is gonna be basically what does E equals MC squared mean? And in my mind, it doesn't mean you have a train and you're going faster and faster and it gets heavier. Like that's not what it means. It means that if you have a proton or a neutron, it has a different mass, depending on how many other protons or neutrons,
18:14
are stuck with it in the nucleus, which is bonkers. I know quantum mechanics is bonkers, but apparently true, so that if you smush some stuff together, like we do in the sun in fusion, you end up with a smaller mass at the end than you did the beginning and that all converts into energy. And the same thing is you had something big and it splits up, because the mass it's a curve. If you have a big thing and it splits up with fission, also, you get energy.
18:50
So, that not only explains why we get the energy of nuclear bombs and nuclear reactions but also how we get the energy from the sun and much of the energy from the center of the earth. And basically most of the energy that we have is from E equals MC squared. So, it's gonna be on how Marie Curie's radium
19:16
and Einstein's E equals MC squared, change our view of reality. And that is also going to be the subtitle of my next book. It's gonna be called, "The Radium Revolution: How Marie Curie's Radium "and Einstein's E Equals MC Squared Change Our View "of Reality." I just repeated myself. Anyway, so that one is coming out sometime. (presenter laughing) I'm making no predictions of how long it's gonna take me to get this stuff done. Then the bonus feature is why so many people seem to think relativity,
19:53
not E equals MC squared for some reason, they're fine with that one, but relativity is often called pseudoscience and why so many people are particularly focused on that which unfortunately brings me back to talking about Nazis again, which is a little stressful. So, we'll see if I feel like doing that. And then after that, I'm gonna go back to my evolution of wireless thing. About four years ago, I promised to do a video on the history of television
20:24
and then I'm gonna get to radar and cell phones and microwaves, all sorts of cool stuff. Now, some of you might have noticed, it's been a long time since I last made a science video and some of you might notice that I have a brand new set and those two things are related, because about three weeks ago, I moved about 15 miles south of San Francisco and although I love my new home and I love my new set, I did not love moving and it's a good thing I love my new house, because if I didn't,
20:59
I still wouldn't move because moving was horrible. You might think that with all that stress, I didn't get much done, but that actually wasn't the case. I did a lot of research and a lot of writing and a lot of preparing, but what I didn't do is finish anything. And I thought, "Well, I'll just be extra creative. "And then the second I'm done moving, "I'll be extra productive." After trying to be extra productive for about a week, I realized that's a way to go extra insane.
21:31
Okay, well, I hope you liked that preview. Also, I have a lot of other videos to entertain you. If you hadn't read my book, "The Lightning Tamers" about the history of electricity and how it got into the homes, please read it. I have a GoFundMe to make a audiobook, which is about I dunno, halfway, three quarters way through which I'm fine with because I'm so busy. But I also really wanna make an audiobook, because I know a lot of people prefer reading that way
22:04
and I've never done an audiobook before, so I do not know how long it's gonna take but that's in the works as well. I hope you are excited as I am. Well, you're probably not as excited as I am about all these and because I'm so excited. It's gonna be so much fun and I'm so happy to be back making videos. Okay, stay safe and curious my friends. Oh, and I forgot to thank my patrons. Thank you patrons for putting up with me. If you wanna join their ranks
22:37
and have me thank them for putting up with me. I have a link down below. Okay, thanks a lot, bye.
Here to help you learn
Sign in to keep a private conversation with your course tutor.
Ask me anything about the material…
Sign in to chat