I thought this pinned comment could be a good place for people to add (respectfully) things in history and physics that you think I made mistakes on or need more clarification. Please nothing about sound quality or other superficials in this thread. Let me start: I wish I had added that when a battery is in a circuit the chemicals take a while to react, so that the electric potential difference from the charge distribution Delta V is less than the emf, or the chemical potential energy per charge. The equation becomes Delta V = emf - ir, where i is the current and "r" is the internal resistance. This is why a battery heats up when you have a lot of current flowing through it. 11
I sent you by email the PDF of a highly relevant paper on the very subject (Galilia and Goihbarg, 2005). You did not use it. Have you got it? BTW, I also think you misstated something about Feynman because you first agree with him and then seem you say that the same quote is nonsense. I've made a separate comment on that.
I'm currently working on a video debunking his video about the direct downwind faster than wind cart powered only by wind. I was going to do do a video about the DC electricity video. To me this two are very similar and both have to do with understanding what energy is and the fact that energy storage is as important as friction in physics but much less disused. My simplification of Derk's DC setup will be using a charged capacitor instead of the DC battery and a discharge capacitor instead of the light bulb. I used this analogy and people have a hard time understanding why after the switch is closed assuming the two capacitors are identical just one fully charged and one fully discharged why only half of the energy will be in the two capacitors as half was lost as heat in the wire then radiated from the wire to the outside. And yes the switch is a capacitor and you can transfer energy to the light bulb by only moving the contacts closer to each other without closing the switch so mechanical energy used to move the switch contacts will get dissipated as heat including in the bulb filament but no energy has left the battery if you return the switch contacts to the original distance.
The energy required to charge 30, 000 KMs of conductor, seems to be the limiting factor till quantified, the problem can continue being solved from there. Quantum is a synonym of the word magic, it only remains so till explained using correct nomenclature rather than ambiguous bucket-terms.
Why do you jump from one name to other, then continually admitting you did not understand, did not learn it and you disagree. Your only credentials is that you showed up in the class and looked at many science cartoons. Fineman put science on the map, what have you done?
Alpha's video proved, (in my view) that a transmission line is not the same thing as power supply. If the wires coming from the battery were perpendicular to the wires supplying the "bulb", you wouldn't even see much of a spike. And in any case you would not see continuous power.
@@zhoufang996that video of Voltage waves is totally amazing and stunning. It truly makes the behavior of Voltage look like water. I'm a student in Electrical Engineering and I can't stop thinking about that freaking video.
When I was studying Electrical Engineering in the early 1960's we first studied DC and Steady State AC circuits at lower frequencies. Then later we took a class in Transient Circuits and that introduced the concepts of electromagnetic waves and high speed transient effects of electrical conductors, spacing, conductor geometry, electric fields, magnetic fields and high frequency effects on circuits. Then we studied transmission lines, waves and antennas which then lead to Smith Charts and impedance matching and wave lengths, etc. I think what got Vertasium confused was conflating the 'transient' charge effects with the 'steady state' current/energy flow. Certainly an oscilloscope will see a 'pulse' of electric charge after the switch is closed but the light bulb required steady flow of electrons to create an (I^2 x R) energy flow to heat the filament and then create the light energy. Those two events don't happen at the same time. If all we wanted was to create an electromagnetic pulse then our house wiring could use hollow copper wires or 'wave guides' as microwave antennas us to move electromagnetic pulses around the house. However we need electrical energy to continuously flow to light bulbs and move motors, etc. so we must use 12 Gauge wire to move 20 amperes of current in a continuous manner to move energy without overheating the wire as the National Electric Code requires for all houses. The center of the wire as well as the outer part of wire all matter when you are transmitting DC or 60 Hz AC current flow to light bulbs, appliances, motors, etc. Of course if you are transmitting megahertz frequency signals to an antenna then the rules change but that is a different matter as I studied in college. Thanks Kathy for helping clear up the differences in electrical concepts of current flow.
The only difference between AC and DC is whether the current flows through the valence electrons or the conduction band. While the conduction band is closer to the heart of the molecule it is not the "center of the conductor". It is not like the "flow of water in a pipe" that's a blatantly false analogy. Electron drift is from negative to positive. The flow of current is from positive to negative. In the opposite direction. The charge is a virtual photon that pops in and out of existence as the electrons oscillate up and down their respective bands of energy. Most importantly the charge flows in the "holes" left behind the electrons. Not through or in the electrons themselves. That's why plasma physics requires ion's with electron-hole pairs.
@@calinbeale2634i think what everyone keeps getting at is "skin effect" which is frequency dependent depth of conduction. high frequency signaling results in charge density nearer the wire surface. the switch closure could be considered an impulse, which is all frequencies but the initial edge will likely be the high frequency portion exhibiting the skin effect followed by the quiescent dc state. when you look at the voltage signal on the wavefront it's a step function... high frequency initially followed by zero so the depth of interaction should be increasing with time. i would posit both components will raise the filament temperature. but the DC component will result in vastly more power dissipation, which makes the light.
I think Derek's imaginary circuit should have had two switches, one on each side of the battery terminals and closes the 2 switches simultaneously to see when the light bulb lights up? Of course, oscilloscope probes place after each switch, may be Veritasium just published the videos for the views only!
@@calinbeale2634 I was under the impression that valence electrons in a metal are already delocalized into a conduction band and that it is these delocalized electrons that are available to flow in a metal wire, either in a consistent direction under a DC electromotive force or in alternating directions under an AC electromotive force. At low frequencies, such as those used in utility grid transmission, I don't believe there is a distinction between the transport mechanisms for electrons through a metal conductor for AC relative to DC. At higher frequencies, we have to consider skin effect, but even then, I believe it is the same "sea" of delocalized electrons that makes conduction possible.
@gracenotes5379 the one thing I would add is that it is not just the conduction band. The CB is a shell for electron orbital closer in to the molecule. The valance band is a lower energy electron band where the "free" electrons float in a cloud. The electron oscillates between these two shells. When it goes up a band it's because it accepted a virtual photon and gained energy. If it goes down a band than it gives off the photon losing energy. It is the passing of virtual photons that is the electromagnetic wave.
@@WarrenPostma so if we have perfect circle od wire (length 300 000 km, diameter 95541 km ) and we push the switch, will that signal travel just one second ?
@@laurenpinschannelsobviously the veritasium video is already out there. I think this IS an actual example of peer review, in the same way that a response paper would be a form of peer review in the general sense of the phrase.
In order for there to be peer review, the reviewer must address the subject under discuusion, in this case the Poynting vector. All Kathy does is to profess a dislike for it and for David Jackson who includes a discussion in his book. Kathy claims to be a physicist, but seems unaware of the Poynting vector until the present discussion. I was introduced in my junior E&M course and saw it again in graduate school. The Poynting theorem is simply derived by dotting the E vector into Ampere"s Law and then rearranging to form a conservation law for electric energy. The Poynting vector certainly describes the flow of EM energy through empty space. What is needed here is a discssion of the Poynting vector in dc circuits. Kathy throws up a lot of irrelevant facts but never gets around to the real issue. She does make a glaring error by saying the the electric field is the (negative) gradient of the poential, which is only true in electrostatics. In electrodynamics, one must also have a vector potential to account for the unconservative nature of the electric field due to Faraday's law.
I was one of those electrical engineers that reacted to Veritasium's video in a manner that can be best described as "wait a minute, that explains nothing". It's true that an electromagnetic wave needs no conductor, but DC current most certainly does. A lot of debunking of this has been going on since, and lots of good ones at that, so i won't go in to more detail here, but just saying that an explanation with the transmission-line model would have made perfect sense, and that the DC (battery) was a really bad example. I can see that you have been thinking both long and hard about this, and your result is excellent! What bugged me most about Veritasium's claim was the headline "electricity doesn't flow in the wire", well how else can you explain DC current? I'm really looking forward to more of your video's since i find that the historic connection is giving me a firm foothold of understanding, it makes me more grounded, so to speak. (pun intended) :-).
Another EE here. Yes I agree the transmission line model would clarify a lot, and it would explain that the light-bulb mostly likely will slowly ramp up in steps, as you see the reflected wave going back and forth between battery and light, that each have a different impedance than the characteristic impedance of the wire pair. If you look with a scope at the end of a not-terminated T-line you see exactly that. However, the pointing vector does work, even in electrostatics. I applied it myself when I wrote a field simulator (MOM based) to calculate the energy transfer. In this case you need to integrate the pointing vector over a closed surface surrounding the battery or the lightbulb. Voltage is only defined in electro-statics, and doesn’t work well if you have changing magnetic field. When we define voltage for an AC circuit, we use a quasi-static approximation.
Nobody seems to realize that these wire pairs are in fact a networks of resistors and capacitors (transmission lines). Dave and Electroboom get it. But I think this video and Derek's video don't seem to understand it.
@@kriswillems5661 I think Kathy said she had a graduate degree in electrical engineering. If so, she definitely knows what a transmission line is. BTW, you forgot inductor. 😛
@@kriswillems5661Kathy mentions dc circuits, and steady states, but in my non-qualified opinion, the fundamental thing here that closing the switch on this battery / wire / lamp situation creates, for at least an instant, a non-steady state between the two steady states of off and on, and for that intermediate instant this arrangement behaves as an AC system, which is why transmission line theory explains what is going on. Overhead HV transmission lines have a capacitance to ground of several nF/KM, this experiment doesn’t need a light-second’s length of wires to illustrate, electricity leaking away in an AC distribution line is well understood.
Alpha Phoenix just posted a video where he measured voltage at multiple points along a wire. His animation of those voltages wonderfully shows the flow of electricity through a wire after a switch is closed.
Thank you, that was exactly the video I was thinking about when I posted my comment above about transmission lines. The theory is very well established.
Veritasium is often off the wall and somewhere out in left field for fake shock effects. People in YT just to grab a mega audience and make money doing so. You rock, Kathy. The truth wins.
Love these videos!. Earlier today, AlphaPhoenix put out a video called "Watch electricity hit a fork in the road at half a billion frames per second" with some interesting observations and visualizations on DC electricity.
@@Kathy_Loves_Physics It is wonderful. I get lost in the technical explanations, so I'm not sure Alpha Phoenix's video is directly or tangentially relevant to Derrick's video or not, but it seems so.
Part II about Feynman: I believe that he was speaking to religious zealots and other crackpots who are eternal science deniers. He was NOT claiming that you can't explain things to children. I do think you have misinterpreted his words.
in fact feynman was great at breaking things down and simplifying in order to explain them. He just was opposed to saying that the simplified way is how it works. When you simplify something in order to explain it, you should say that it's simplified.
@@tommihommi1 I totally agree, that is the point of the Feynman diagrams and the "shut up and calculate" statement, he was always trying to show that the world is strange and wonderful and how things work as opposed to how we understand things work as they can often be mutually exclusive and that is what science is about teasing those two things apart to see what is real.
@Weirdly_wonderful I think I agree with the other commenters, here, about your take on Feynman's quotes which you said were about "education." I don't view the segment that you used about education or about speaking as "handed down from on high," the way you seem to be suggesting in your video. The clip you used was from the beginning of his 1979 University of Auckland lectures describing the theory of quantum electrodynamics (for which he and others shared the Nobel prize). When viewed in the rest of the context of that video (and especially that segment of his first lecture in the series), my interpretation of what Feynman was describing in that quoted section of video was "I am not going to make a fake analogy to give you some false impression about how this theory works, but because of how crazy the calculations look, or how strange the conception of the models may seem, you may not accept the conclusions we get to draw from this model and conception of how nature works. If you don't like that, you're either welcome to move to another universe where the rules are simpler, or try your hardest to come up with a different explanation and conception that fits what we've observed." In my view, this just expresses Feynman's personality and general commitment to not taking shortcuts in trying to give explanations for how things work (according to "the human beings who have struggled as hard as they can to understand it"). He says he can't make it simpler, because at that time (and as far as I know, even now) we don't have a simpler conception of how nature works, at that level (explaining quantum electrodynamics). But in my view, it is not a general remark he is making about explaining all of physics or a general remark about the nature of education. Would you agree with that?
Totally agree. Wasn't it Feynman that said "if you can't explain it to a child, then you don't understand it yourself" (or something to that effect)? So no, I don't agree with Kathy in her view on Feynman.
Eric L Michelsen touched the right point. I suggest reading Oleg D. Jefimenko’s Electricity and Magnetism, topic 9-5. Displacement Field and Static Charge in Current-Carrying Conductors for clarifications about the static fields in conductors when steady current densities are present. Jackson’s 1996 paper indicates this when saying: “With the early notable exception of Jefimenko’s book, intermediate or advanced texts are no better”.
Another very good response to Veritasium's videos. One of Derek's reasons to make the original video was to spark discussion. I think you misinterpretted Richard Feyman's comment about keeping it simple. Einstein once said "God does not play dice" The response was "Eistein, you cannot tell God how to make the rules". One of Feynman's strengths was, "if at first you don't understand what you are looking at, then don't say physics doesn't make sense. Try looking at it differently till it does ".
Thanks; I was very confused by the Veritasium video which I was never able to digest. AlphaPhoenix just posted a series of videos that made much more sense in which he modeled charge as waves as it moves through wires. It struck me as logical and well presented, and so is a strong recommend.
I think Feynman's quote to be one not about education but one about the scientific community. I like this take quite a lot. To me it's in the same vein as Tyson's "The universe is under no obligation to make sense to you"
Agree. Feynman was very much in favor of education and explaining and there is much evidence for that view. Here he is pointing out that he's going to be brutally honest in giving an explanation and won't oversimplify it for the listener, which would be dishonest. He says the same when explaining quantum mechanics of light. I love your history lessons Kathy !
@@fotrj No, he wanted people to accept the concepts of modern physics even if those concepts go against our intuition. If some lay person tells him "time dilation is absurd, your math must be wrong, come back with something better", then he will tell that person to go somewhere else.
Yeah - there is just one problem. Shinola gets 20Million views and a $100K check from youtube. Science gets 2000 views and lucky if it gets to million.
I thought seriously. about creating lots of new accounts so I could like this video a bunch more times... Kathy, thank you so much, I still have tears on my face because of your kindness and humility, not to mention all of your hard work.
...and I think I can reconcile two of my favorite science educators in my mind. Feynman frequently tried to be dramatic in order to engage his listeners and at heart is a theoretical physicist. Kathy is, at heart, a teacher, and to you, it is the teaching and communicating. Feynman wants the student to already have a complete grasp deep within maths. Kathy, is happy to explain in simpler terms. I like Feynman. I love Kathy. I have Feynman's lectures. I watch and re-watch Kathy's TH-cam stuff to refresh my mind and reeducate myself for all the stuff I forget or forgot. Thank you, Kathy, for making me very happy. Thank you, Richard, for your contributions to science, too.
Feynman is happy to explain physics. He does that in his lectures. But he will (very obviously) refuse to bend physics just for the sake of people who reject concepts that contradict their intuition. That was his whole point. It had nothing to do with how to teach physics. Kathy misunderstands Feynman completely on this point.
I love these historical perspectives! Much of modern science communication is so difficult exactly because it is unaware of the original progression of discoveries that made us understand these processes in the first place. I think we should teach most topics by repeating the original discovery, with newer information only added in where they really make it easier to understand.
Well, I made some work about Poynting vector especially in quasi-static cases (in the circuit frame). According to me, there is nothing wrong with the present theories, only a poor understanding of the Poynting theorem I am afraid. The Poynting theorem doesn't say anything about the actual flow of electrical energy. Worse it gives infinite possibilities to define the energy flow through a vector field, all leading to the same balance. I have shown in one of my articles (published in the AFLB journal), that you may define an energy flow in a capacitor not going outside radially but axially (parallel to the wires) as your intuition suggest, with the same overall balance. More technically, you can add any rotational field to the Poynting vector without modifying the energy balance. Discussing where the energy flows from one point to another point is pointless :-) both in Maxwell frame and in the QED frame (In the quantum frame, the trajectory of a photon is not more defined). You may consider the flow of energy in the wire, or outside it like Derek and many others, or in circles as Feynman introduced in its course to illustrate the idea of the indetermination of the energy flow (you should have followed the entire course instead of extracting only a short portion of it !). If people generally use the cross product definition it is because it is clearer to describe waves propagation in vacuum, and also because its a relativistic invariant, but this is another problem we may discuss another day. The philosophical question about the actual path of electrical energy flow remains open I am afraid !
I'm Eric L Michelsen, but Google is scrambling my name. To clarify, I'm affiliated with the University of California, San Diego (and my last name is spelled "...sen"). There is much interesting and useful material in this video. For example, I have given a talk describing simple experiments which show that power does NOT flow along the Poynting vector, and that is fully compatible with electromagnetic theory. For reference (but not claiming infallibility), I have a BSEE, and a PhD in physics, and decades of experience in laboratories and measurements; I teach this material at the upper-division college level. However, I think it is well established that the electric field inside a current carrying wire does, indeed, drive the current, and that this field is created by surface charges. Conductors can expel E-fields only in a static (or quasi-static) system. In contrast, a DC circuit is a steady-state dynamic equilibrium, and though the charges in the conductor move to reduce the E-field, the battery is constantly "pulling" them out of (and "pushing" them in) the wire, so they can never cancel the E-field completely. It takes only a tiny E-field in a good conductor to drive a significant current. This is established by extensive experiment, and organized into the detailed theory of electromagnetism (with no deference to anyone's authority). I have a detailed discussion of the speed of electricity and the Poynting vector in my "Funky Electromagnetic Concepts" (at the bottom of my web page), starting around page 69 (as of this writing). I performed (the moral equivalent of) Derek's experiment, and confirmed that in some very realistic situations (but not all situations), the bulb turns on nearly full brightness, nearly instantly (as expected from theory). My document includes photographs of my setup and results, and a discussion of the theory, but is written at the upper-division college-physics level. This is all well-established science, and fully consistent with relativity. (In Dr. Muller's follow-up video, I think he actually didn't give himself enough credit for his prediction.)
The fact that people are STILL posting responses to that video gives me faith in humanity. I watch them all and every one teaches me something new, a slightly different perspective for thinking of how electricity works. Great one from Kathy here, with an illuminating historical perspective. For all the problems of that original video, hats off to Derek for pushing many of us to look beyond the elementary school depictions of electricity.
Have you seen AlphaPhoenix's recent video? Especially his second channel further explanations about impedence matching? I find it a great explanation as well.
You confused me when you first present Feynman as rejecting the Poynting vector theory, but then state that you reject Feynman's material on the Poynting vector. After checking the Feynman text in its proper context, I noticed that he gives further explanations why it "isn't so terribly puzzling" after all, with the right way of looking at it. Btw, in the "go somewhere else" video Feynman was NOT saying that some people may just be too dumb to learn physics. He is just criticizing people who have decided to reject stuff like quantum mechanics and relativity because it is "too crazy". Feynman's reply is that if you don't like this crazy stuff, go to a universe where the rules are simpler. And it mystifies me why you should even consider discounting the physics work of Feynman just because you (falsely) believe you disagree with him on a point of pedagogy. All in all, this video does not paint you in a very good light at all.
If you listen to Feynman he actually says that the theory (Poynting vector for energy flow radially into a DC carrying wire, etc.) is correct. He further says that our intuition does not match the theory but this is ok. Poynting (1884) shows that the energy (per unit time) flowing radially into the wire is actually the same as the power given by the much simpler, V*I. V*I is just much easier to calculate than the Poynting vector but it doesn't say anything about where the energy comes from (the E and B fields). All electromagnetic theory has to be expressed in terms of fields, the 'flow of electrons' is just a sideline. A full treatment would of course use Quantum Electrodynamics whuch brings us back to Feynman 😁 (Melrose's Quantum Plasmadynamics, may be a better jumping off point for someone interested enough to do the full calculation or at least draw the Feynman diagrams).
I've looked at almost all the comments. It seems Kathy doesn't want to respond to critiques that the Poynting vector is correct for DC circuits. She took Feynman out of context. Her rationales for not trusting the Poynting theorem are not strong enough and don't stand up to scrutiny.
I am a BSChE about ready to retire in 15 mos. Going back to my alma mater to get a degree in physics. Been watching MIT OCW (diff eq to refresh after 40 years) and Elliot and ViaScience... and you... and some others but your videos are fantastic. Thanks Kathy!!!
Love the actual experiments you’ve done! Great channel that I have frequently used before giving lectures to give some human interest to where these equations come from in the first place. Great book too!
I admire your videos. But now, i'm in love into them. You're great communicator and reinventor of old wonders and stories. Thank you for the great work. Looking forward to more videos
With dc it's the electric field IN the wire that drive current and power IN wire and ac will be totally different. Sounds like you are correct. Great video. Thank you
What Feynman was saying is that the universe has no need to be simple ---in terms of linear, intuitive to human understanding etc---and that one must accept experimental evidence over a neat simple concise but wrong theory. In terms of his views on education, there were two main sentiments expressed: 1) If you can express something in a way that ordinary people can understand,,then the likelihood is that you don't understand it as well as you think (that's his famous meme on learning) 2) Somethings in nature cannot be explained without first explaining a whole gamut of mathematics except by analogy. The second sentiment was expressed in an interview where the interviewer had asked him to explain how magnets work and why. Feynman could go only so far before he needed to upgrade the individuals maths skills. I think that your notion is entirely true in that: anyone should in theory be able to understand anything scientific; however, the depth of understanding does depend upon having or possessing mathematical ideas once you go beyond certain levels of knowledge.
Kathy, I bought your book and wow, so much good dope, kudos! I love history, and electronics has been a hobby of mine since 5th grade! I am self-taught in engineering, as I have no aptitude for a school environment, exams and drinking lectures as if from a fire hose.
I love your videos, I used to have electronics as a teenage hobby and one of my uncles was working as a microwave electronics consultant in the 1970s here in Australia. I identify with all that you say. Lots of love from David Newton x
Actually, as you well know, Feynman did a a great deal to make physics understandable to people. Who is perfect across all areas at all times in their life.
Honestly, I don’t understand your confusion. I don’t think it’s good for someone to put something that they think is obviously nuts and crazy in a textbook. Also, I do not know that he did “a great deal to make physics understandable to people”, as I’ve never seen a single example of that. I’m not asking for perfection, I’m asking for kindness. But I have not watched/ read everything that he did. Maybe he was kind and relatable in other areas. I just haven’t seen them. Also, we are allowed to have different opinions. I’m allowed to think negative thoughts about Feynman and still be a physicist right?
@@Kathy_Loves_Physics absence of evidence is not evidence of absence. Seeing involves looking. Maybe you have a responsibility to investigate properly, as you do for the characters you write about, before making such a public statement. Feynman did not have the attitude you claim, quite the reverse. Disappointed.
Warren, I am particularly interested in your use of the word quixotic. Quixotic is a reference to one of my favorite novels Don Quixote where a poor farmer decides that he is a knight, and a windmill is a dragon that he cannot defeat. But I don’t get what that means in reference to my video. I mean, you could be saying that I am not really a physicist, just as Don Quiote was not really a knight. But if that’s the case, then my complaints about Richard Feman are quixotic means that Richard Feinman wasn’t a physicist either, he’s just a windmill. Care to clarify?
It is hard to separate what Feynman did and what he claimed he did. The guy was an extremely good story teller and had a sizeable ego. That and he had a very poor attitude towards women. Kathy has every right to be suspicious of him, I can only imagine the amount of sexism she has put up with in this field.
I remember when his first video on this came out and there was a big reaction and discussion to it. I feel it was the perfect educator situation, since it forces someone to really start pondering how all of it works before they can even start to come to some conclusion of their own. In the end, the places where he was wrong seem mainly to be from oversimplifying for pedagogical reasons, and slips of wording that were wrong or make it debatable what was meant, all of which allow for misunderstanding (since I am sure Derek himself understands this, it is more a matter of presentation). It is great that even after all this time, people are still making responses to it, and getting people engaged with the details of how it all works.
When you close the switch, positive charges start to spread on the plus pole, and negative charges start to spread on the negative pole. These charges cause on electric field. On the positive side, with the positive charges, the field pushes away positive charges in the parallel wire, on the negative side the field pushes negative charges away in the parallel wire. So an unbalance is created in the parallel wire and a current flows and the light goes on. This happens after 1/c seconds, because the field only need to travel 1 meter. It's pretty simple, both wire pairs act as capacitors. And DC pulse passes the capacitors (but a continuous DC voltage does not). The continuous flow of current happens only later when the electron flow in the wire starts. This happens much later. So, the bulb flashes after 1/c seconds, but it is only stable much later on.
The electric field inside a wire is only zero when there is no current in it. If it's carrying a current and it has resistance, there will be a charge gradient along it and therefore an electric field.
Very interesting video. I'm curious if you have seen Nick Lucid's "Science Asylum" video from about 4 years ago titled "Circuit Energy Doesn't Flow the Way You Think" and what your thoughts might be about it.
Great video!! Im interested if the cucit, but instead treated like a large circle and not two paralell conductors (EMP travel at light speed.) will this relate back to Cosinus to f ,and electrical motors?
I'm sorry but that's really not how batteries work. All chemical cells are based on specific redox reactions occurring within them. Some of these do use acids or bases and metal electrodes as their reagents but others do not. Their common element is that half of the reaction (reduction, which consumes electrons) occurs on one electrode and the other half (oxidation, which generates electrons) occurs on the other electrode. The simplest cells will achieve this by making the electrodes from the reagents, but _there are_ plenty of cases where one, or both electrodes take no part in the reaction. You can keep the electrodes in two different solutions connected via some sort of an ion exchanger. You can cover the electrodes with a catalyst. There are plenty of options. And second of all, when the battery is not yet part of the circuit, the reaction indeed isn't occurring. But that doesn't mean it can't give you current right away - as soon as you complete the circuit. The reaction isn't progressing precisely because it has progressed the furthest it could get, building up charge on the electrodes, internal wires and the terminals. And finally, the heat generated from resistance is frankly negligible. The vast majority of heat will be produced in the chemical reaction itself.
I appreciate the time and effort you put into your videos, but my utmost appreciation is towards your tone. I love how measured and thoughtful your videos are. You make the topic very approachable for the newcomer, but also have enough detail and complexity for a well-rounded presentation. Your respectful response to his video is how such videos should be handled.
I agree fully with Feynman's statement. My interpretation of it, based on some wider context, is that he saw simplification as inherently untruthful. He was well documented happily spoon-feeding complex topics to any level of audience. The important semantic detail is that simplification of a complex thing is an arbitrary modification of the thing, and not equal to dividing the thing into manageable components for learning. Simplifications taught to children are very often a major source of trouble later in their education, and even in general life, because you have constructed a faulty foundation and now the entre first floor needs a complete tear down and rebuild before the second floor can be added. (This applies to any introduction level education, not limited to children.) In short incomplete (building blocks) and incorrect (simplified) are different things.
It was like engineers arguing with physicists. In Electronics, we have a number of models and tools to design our gear including conventional current which is opposite to conventional flow. As a tech, I was first taught electron flow and regret it to this day. It’s like learning imperial system instead of metric. I learned about skin effect in AC but I see there’s a lot more to this than I realize even though I really don’t need to know it for my daily tasks. Socratic method of asking and answering questions to arrive at a truth…like the Paper Chase. I enjoy the deep dive down the rabbit hole to Wonderland by all the creators on this subject.👍
I started as an electronics tech in the Marine Corps, and they taught electron flow. It seemed odd that current would flow against the arrow of a diode symbol. However, that was still the era when vacuum tubes were in use, so there is some sense to talking about electron flow. That school was pretty basic, and raised enough questions in my mind to motivate me to become an electronics engineer.
@@SkyhawkSteve There was... at least some... American profs writing textbooks using electron flow (versus conventional current flow)... but, AFAIK... and apparently... it never caught on. Eventually, I think, everybody promoting electron flow gave up trying to change it.
Electricity, Magnetism, Heat, light / Color, Mass / Weight are different manifestations of Gravity and Continually convert to each other. Gravitational Particles (GPs) move by means of CONDUCTIVITY towards the CENTER of the GRAVITY. Turbines convert the Gravity Force to Magnetic > Electrical > Heat > Light and everything in between. When GP moves in the Air (4N1O) Atoms are manifested as Magnetism, therefore Magnetism exists only in the Atmosphere and is absorbed by Compass measured in Air Gap and Magnetic Flux context. When GP moves in Solid it is observed as Electricity and measured by its Power/Force/Voltage and its Current/Amps and their combination total Quantity of GPs in a unit of time as Wattage. GPs move at a 90 Degrees Angle relative to their path in [side] Steps, therefore the GPs manifested as Electricity, Magnetism, Heat and Light transit to the Outer Edges of the Medium/Matter.
Thank you for the video, I unsubbed from Veritasium because Derrick lacks Veritas - he writes too much clickbait, which we already have way too much of.
I think veritasium video mixes two topics, the steady state and the EM pulse. EM pulse: you have to treat it like a transmission line. It will move some electrons in the light bulb about 1/c seconds later, but not enough to light it up. Bulb will light up only after the signal will be able to "check" the continuity of the whole circuit (otherwise superluminal messaging would be possible). Regarding the steady state, once all the oscillations of the initial EM pulse have been dampened out: to me it seems only a matter of modeling. The most common model is that of electrons pushed through wires. The moving charges then cause EM (static) fields as a consequence, and, curious coincidence, a Poynting vector appears. But, you could easily say that, lying the conductor in a certain way, you put some constraint on the shape of EM fields, which carry the energy and, as a curious coincidence, electrons in the conductor start to move. Either way, you can't have moving charges without fields and viceversa. Choose the model that fits best, especially, the one that is easier to apply.
My initial comment was blocked (maybe this one won’t be). I would be delighted to debate … but I can do so only through e-mail. Huge respect and admiration from Romania.
I'm only 1:15 in, but I love you already Kathy. I am not a scientist, but when I first watched the video at Veritasium, I was deeply disappointed by his simplistic approach. I am reminded of the fact that science progresses because good theories get replaced by better theories. NOT because of bad theories being replaced by good ones. It is a process I refer to as "Continual Refinement" and I try to apply that process to myself. And of course we must understand that Kuhnian paradigm shifts take place in science, and how messy they can be, because science is performed by humans with big egos.
I avoided watching Derek's click-baity piece and the responses for all this time, waiting for your take. AlphaPhoenix's careful measurements are also very fun and clear emperical evidence. You rock.
I think energy is just an accounting thing in physics. Energy is defined as the ability of a system to do work. If a system do work then its energy is decreasing, and the energy increases on the other system that the work is done on. This continues until both systems are in equilibrium and neither system can do any work on the other. The physical thing here is work and not energy. Like in accounting, my work is the physical thing and the money I get for it is just an abstract accounting number. So energy doesn't really "flow" as in something physical like water flowing in a river. Something physical must do work. "Energy doesn't flow in wires" is really nonsense, energy doesn't flow. What happens is that a field is created, that field is doing work, pushing the charges, those charges collide with other charges, change the orbitals in the bulb, those orbitals decay releasing a photon (which is also work) and the light bulb lights up. Mass as a form energy comes also from work done. About 99% of mass comes from the complex interactions of quarks and gluons in the proton, which is work. 1% of mass comes from the interaction with the Higgs field, which is also work.
I think this wholly comes down to semantics and what it means to "light up" the bulb. It also seems to have some relationship with the difference between the maximum speed of causality and the propagation speed of "meaningful" events in the physical world.
I give you 2 thumbs up! I don't really understand all things electric but I do have a great fascination with them. When I watched Derick's video on how long it would take to light a bulb I felt uneasy with his explanation although I wouldn't have been able to verbalize it. Your video helped my understanding of my original unease. I also greatly appreciate your definition and comparison of true science vs psudeo-science. Thanks for posting.
The timing on this video is perfect as Alpha Phoenix just released a video about a similar thing, but his explanation of what’s happening felt a bit lacking to me.
As a lay person I've noticed that no matter the subject, a lack of historical perspective can be fatal to clear thinking. I think anyone who wants to study a science needs to retrace the path of those that went before us. Thanks for applying that principle to physics.
You said, "It was because of Feynmann's comments on education that I started discounting all of Feynmann work." This betrays a fundamental principle of science that we look at the science, not the source. Anti-scientists use this technique. "Oh, he believes in climate change, so I won't take his studies in geology seriously." Feynmann's improtant physics work was peer reviewed. So, you are also discounting peer reviewed science, including I suppose quantum electrodynamics. I also have to point out that the lecture you showed a clip of was Feynmann at a QED lecture. The audience would be expected to understand his point. Facts (and observations) are the proper test of theory. It was completely irrelevant as to education of children. So, clearly taken out of context. Real context: In April 1966, Feynman delivered an address to the National Science Teachers Association, in which he suggested how students could be made to think like scientists, be open-minded, curious, and especially, to doubt. (From Wikipedia)
Well, people often make the mistake of confusing the message with the messenger. It's actually a logical fallacy. If you want to attack an argument, attack the argument - not the one who is putting it forward. However, confusing ideology with how the world actually works is often producing this result. Which is a pity, because by very nature any ideology is internally inconsistent.
When I was in college, the professors acknowledged that the electrons flow from - to +, but to keep the math easier, we engineers cleverly came up with hole-flow theory... as an electron moves, it leave a gap, so the one behind that comes in to fill that spot, but it left a hole and the next one behind that moved to fill that gap, and so on. If you look at this gap, or "hole", it is moving from + to -, hence hole-flow theory.
Albert Einstein is said to have stated “If you cannot explain your theory to a seven year old, you do not understand it yourself”. I agree that anyone can understand any of the concepts in science if they are properly and concisely presented. I enjoy the presentations on this channel because they are presented so.
Maybe Einstein wasn't right about that. But your later statement is patently false - there are scientific concepts that are outside the reach of some humans. This is true also for me, there are things in science I know I csnnot fully grasp.
Finally someone who explain it. It bothered my mind all these years because it's illogical. As you describe, if we move the switch in any measure, the result will be changed.
I'll have to study all these video's to see how it stacks up to what I've been taught and also to adequately know what everyone is posing. Fortunately the subject at hand doesn't make any difference to current carrying capacity as we know it, but is interesting as I have been taught differing things throughout my life. 43 years ago 1980 at high school everything current, field, electron flow all went at the speed of light. As an Electrical technician doing a physics refresher course over a year in 2008 to keep the brain cells firing we were taught the electrical field is created at the speed of light but the electrons themselves move in a sporadic motion as they bounce and collide with atoms in the whole conductor and as such the actual distance travelled along the conductor is very low with out getting into differing variables, voltages etc. I'll have to watch the the original video in question but was confused when Cathy brought static electricity into the video. I love your video's Cathy they are a real treasure.
I thought that in the condition where the bulb is very close to the switch that the bulb would light immediately, similar to the time it would take if the circuit were of small size rather than half way to the moon (or whatever the distance was). I assumed this based on the circuit would be in a steady state prior to closing the switch and there would be a difference of charge potential across the switch, and the charge in the wire on the long end would be constant along it's length. When the switch closes, current begins to flow immediately because of this difference in potential and as the current moves along the wire it continues to provide difference of potential as the charge from the far end of the long wire eventially catches up. OK maybe I did a poor job of explaining that. It's late and I'm tired. It was fun to think about though. And no, I don't recall any mention of Poynting Vectors during my education either.
As a Master Electrician and keen viewer of your videos, can you please tell me if you think electrons go forward and backwards in an ac circuit. If so, how far backwards and forward do they travel. I've looked in my text books and spoken to my associates, but no one has a definite proof. Please help , thank you . John M French.
Yes I think you are correct Kathy. Poynting Theory does not distinguish between potential and kinetic energy so flow that seems unphysical will probably be potential energy. With dc there will be energy flow inside the wire.
The Poynting vector itself does not represent energy flow. If you integrate the P. v. around a closed surface, the result is the net energy entering or leaving (depending on sign) the enclosed volume. Alternatively, the divergence of the Poynting vector indicates if a locality is sourcing or sinking electromagnetic energy. Feynman was addressing the view that the vector itself represents energy flow.
But note that Feynman does agree with the theory which is "obviously nuts". His point is that the theory goes against our intution, but that does not make it wrong (and if you don't like it, then I guess he'd say you can go somewhere else). Feynman also points out that the practical consequences are near zero, and I very much doubt that it has any real relevance to Derek's question. "Energy" is anyway mostly a bookkeeping device.
@@ronald3836There is this one experiment that you could theoretically do where you measure the gravitational field generated by the energy and energy flux distribution. However carrying such experiment in a lab is beyond current technological capabilities and as far as I know no one has postulated a way to do it with astronomical observations. This video was clearly convinced out of ignorance tho, she only ever appeals to intuition and doesn't provide any real argument against poyntings theorem being applicable in a physically meaningful way to DC circuits.
@@marcossidoruk8033 That would be a very interesting experiment indeed. I guess "energy is just a bookkeeping device" might not sit so well with general relativity. But I do think it is correct to say that we can't help to think about physics in terms of abstractions which the universe itself does not necessarily care about. And of course that is why we do experiments to find out how far our abstractions can take us. There are these videos about "gravity is not a force", but that presumes that the Newtonian notion of "force" is more than a very helpful abstraction.
What a great video. Honest, Respectful and Fearless. In many ways, I hold yourself in the same regard as Sabine Hossenfelder, for whom like yourself I have a special admiration. I should add that similarly I have the upmost respect for Derek Muller who is without doubt a great mind, if (IMO) a tad arrogant, which is a quality I'm not overly fond of. End of my unsolicited 2 cents. /s:)
Derek could've saved himself a lot of grief if he'd just used correct units. 1/c seconds doesn't make sense, it doesn't solve for time. Without showing where the "1" comes from, the answer appears to be the inverse of c, regardless of the wires proximity. In units, his answer is 1/(m/s)=m/s, a measure of speed. If 1meter is used then m/(m/s)=s, a measure of time.
I had the great misfortune of having to useJackson's Classical Electrodynamics book in my graduate classes in the 1970s. It was impenetrable then, and it''s impenetrable now. Like gravity, I think we still don't really understand EM.
Thank you for the fascinating video. Wondering if we change the switch with the transistor (I guess transistors do not emit emp pulses) will it affect outcome of Veritasium experiment?
TH-camr Alpha Phoenix just did a pair of absolutely brilliant videos where he tracked the progress of electrical pulses down a twisted pair; it’s by far the best explanation (and demonstration!) of transmission line theory I’ve ever seen. Check them out, I think you’ll find them as interesting as I did!
Has no one ever used an oscilloscope? A scope especially with storage will show the transients and provide an way to measure them. Modern scopes can go well over100MHz and can easily capture nanosecond events. It might also be interesting to use coax instead of bare wire.
It feels like you are taking Feynman’s comments on the Poynting vector out of context. The Poynting vector is a measure of energy flux, and that’s by definition, there isn’t anything to argue about there. What he was talking about is a bar magnet next to a battery, where no power is either provided or dissipated, but the Poynting vector is non zero, seemingly indicating that energy is flowing in circles, which is not intuitive, but is still true. To say that the Poynting vector doesn’t work at DC, or that it isn’t accurate is wrong, it works because it is defined to work, it is an extension of Maxwell’s equations.
Kathy, I love your work! I have watched all your videos and bought your book. As an electrical engineer (no degree, self taught. As you say, kids can learn anything!) I was quite upset with Derek's video. (I call him my cousin because we have the same last name, but we are unrelated.) I agree with you that the answer to Derek's video is E) None of the above. As you say, it depends on the characteristics of the light bulb, battery and wires. The problem is, the long wires going to the Moon, and the opposite direction, form transmission lines. A transmission line can be modeled by inductors in series and capacitors in parallel. As the switch is closed, current instantly flows into the first inductor, and charges the first capacitor. Then it flows from the first capacitor through the second inductor into the second capacitor. The pulse of current and voltage propagates down the transmission line, through each inductor and across each capacitor, until it gets to the other end. Then it reflects back. In reality, there are an infinite number of capacitors and inductors in the transmission line, but the circuit can be simulated by using a finite quantity and still get good results. The point is, the cable has so many picofarads of capacitance per meter, and so many microhenries of inductance per meter. The transmission line has a characteristic impedence, which is determined by the ratio of the capacitance per meter to the inductance per meter. Let's say you use a coax cable, like my TV antenna does, for the two wires going in opposite directions. The cable on my TV has an impedence of 75 ohms. And let's say the cable has no DC resistance. The transmission line will act just like a resistor with the same 75 ohm impedence, until the reflected pulse comes back from the other end. And let's say the light bulb has an impedence of 150 ohms. So, the instant you close the switch, the battery and switch is in series with the cable going to the left, the lightbulb, and the cable going to the right, for a total impedence of in the cables equal to 150 ohms. Because the light bulb's impedence is also 150 ohms, the voltage across the lightbulb will be 1/2 of the battery voltage, instantly. Note that the speed of the pulse through the cables is also determined by the inductance and capacitance per meter. That is how Maxwell determined the speed of light from his famous equations. And that is because empty space itself has a capacitance per meter and and inductance per meter. They are called the permittivity and permeability of the vacuum, and they can be measured easily. (Einstein knew that the speed of light in a vacuum is constant, because there is no reason why the measured permittivity and permeability of space should change based on the rate your spaceship was coasting through space. The rest of us had to wait for Michelson and Morley to measure the ether wind and find out there wasn't one.) Note also that space has an impedence too, just like a cable. The impedence of space is about 377 ohms. Now, what happens when the pulse reflects off the other ends of the long cables? If the ends of the cables were terminated by 75 ohm resistors, the pulse would be totally absorbed. Because the resistance of our cables is 0 ohms, the only resistance in the circuit would be the 75 ohm resistors at the ends of the cables. The light bulb would still see the 150 ohms total resistance, and it would stay half lit. If the ends of the cables were shorted out, as in Derek's video, the pulse would reflect back and reinforce the voltage pulse going out. When it came back to the bulb, the bulb would see the 0 resistance, then get the full voltage. If the ends of the cables were open circuit, the voltage pulse would be refelected out of phase and cancel the outgoing voltage pulse. When it came back to the bulb, the bulb would see the open circuit ends of the cable and turn off. The whole story is told by the inductance per meter, capacitance per meter, and impedences of the cables and the bulb. Anything regarding Poynting vectors or fields on the outsides of the cables is not needed. Of course, the properties of inductance and capacitance are due to the magnetic and electric fields around the wires, but once those are understood as bulk properties, the operation of the circuit can be easily explained. I think Derek was a little disengenuous in this video. There is a quick shot of one of his electrical engineer experts showing him a graph of the step functions in voltage his light bulb would see when the switch was first closed, and when the pulse returned from the ends of the cables. I know Derek is capable of understanding the theory and math, so I presume he kept that part of the story to himself to make it seem more magical than it really is. Derek is a showman, just like all of us to some extent. We have a duty to our audiences to keep our stories interesting! So, the phenomenon of the transient travelling through transmission lines when the switch is closed is not so mysterious. In your video, you show how sparks from the wires can induce interference in the radio. That is related, because your sparky wires are inducing EM waves into space. But in Derek's circuit, closing the switch is inducing the transient down the transmission line--there won't be any sparks becaue the current is limited by the impedence in the transmission lines. It should also be noted that when the switch is opened and closed, it is no longer a DC circuit. Only after the transients have all settled down can it be analyzed like a DC circuit. Finally, I just want to say that my favorite video of yours is about Georg Ohm, the guy who discovered Ohm's law. I loved how was proven right, and the pompous Ampere was shown to be wrong. I have used Ohm's law many thousands of times throughout my career, and never realized the rich story behind it. Thank you! And my favorite Veriassium video is the one on "How Imaginary Numbers Were Invented." More excellent storytelling! I also loved his video on chaos theory "This Equation Will Change How You See The World". True magic needs no enhancement.
5:57 "Static charges do not affect the electric field in a conductor" That is *remarkably* false. What Michael faraday discovered and whats actually true is that the electric field inside a conductor in electrostatic equilibrium is Zero. The simple reason is that a conductor can be seen to a fair degree of accuracy as a material with free electrons in it, this means that if there was an electric field inside these would feel a force and therefore they would move and that wouldn't be electrostatic equilibrium. For a conductor that's not in equilibrium this statement is completely false, in fact, for a conductor to not be at equilibrium there MUST be a force moving the electrons inside it. This is such a major mistake it undermines the credibility of the whole video, and not the only such mistake btw.
Re Feynman, as a fellow New Yorker (but uh, not a fellow genius) I think he was just getting at there being a level of irreducible complexity where intuition cannot take you and you have to rely on the math, stated in kind of a sarcastic way. Its ok if you take issue with that, but I don’t think he was insulting children there, just that… like, if you want a 5 year old to understand the path integral formulation of quantum mechanics, the 5 year old will need to be a 6, 7, 8 , 10, 15, 20 year old that learns all the intervening math, and classical physics. Feynman is just saying he can’t do that work for you - thats my interpretation.
Delighted Joy!! Keep em coming. Why wasn’t the resistance in the wire mentioned; perhaps because it is a constant (so long as the material in the wire is homogenous-:)?
Thank you very much for doing these well researched video topics with a lot of thought experiments that have been invested in them. Keep this going and take care of yourself. Cheers.
I thought this pinned comment could be a good place for people to add (respectfully) things in history and physics that you think I made mistakes on or need more clarification. Please nothing about sound quality or other superficials in this thread. Let me start: I wish I had added that when a battery is in a circuit the chemicals take a while to react, so that the electric potential difference from the charge distribution Delta V is less than the emf, or the chemical potential energy per charge. The equation becomes Delta V = emf - ir, where i is the current and "r" is the internal resistance. This is why a battery heats up when you have a lot of current flowing through it. 11
I sent you by email the PDF of a highly relevant paper on the very subject (Galilia and Goihbarg, 2005). You did not use it. Have you got it?
BTW, I also think you misstated something about Feynman because you first agree with him and then seem you say that the same quote is nonsense. I've made a separate comment on that.
I'm currently working on a video debunking his video about the direct downwind faster than wind cart powered only by wind. I was going to do do a video about the DC electricity video. To me this two are very similar and both have to do with understanding what energy is and the fact that energy storage is as important as friction in physics but much less disused.
My simplification of Derk's DC setup will be using a charged capacitor instead of the DC battery and a discharge capacitor instead of the light bulb. I used this analogy and people have a hard time understanding why after the switch is closed assuming the two capacitors are identical just one fully charged and one fully discharged why only half of the energy will be in the two capacitors as half was lost as heat in the wire then radiated from the wire to the outside.
And yes the switch is a capacitor and you can transfer energy to the light bulb by only moving the contacts closer to each other without closing the switch so mechanical energy used to move the switch contacts will get dissipated as heat including in the bulb filament but no energy has left the battery if you return the switch contacts to the original distance.
The energy required to charge 30, 000 KMs of conductor, seems to be the limiting factor till quantified, the problem can continue being solved from there.
Quantum is a synonym of the word magic, it only remains so till explained using correct nomenclature rather than ambiguous bucket-terms.
Why do you jump from one name to other, then continually admitting you did not understand, did not learn it and you disagree. Your only credentials is that you showed up in the class and looked at many science cartoons. Fineman put science on the map, what have you done?
A worked example with known values would have been a good way to round off the video I think.
Excellent comment, Kelly, you have pull this out of my lips - “real science makes you think and pseudo science makes you obey”.
Thank you
AlphaPhoenix actually tried to do Derek's experiment practically titled "I bought 1000 meters of wire to settle a physics debate"
Alpha's video proved, (in my view) that a transmission line is not the same thing as power supply. If the wires coming from the battery were perpendicular to the wires supplying the "bulb", you wouldn't even see much of a spike. And in any case you would not see continuous power.
Yes, his videos are very interesting, including the recent ones where he measured and visualised the "waves" of voltage propagating down the wire.
@@zhoufang996that video of Voltage waves is totally amazing and stunning. It truly makes the behavior of Voltage look like water. I'm a student in Electrical Engineering and I can't stop thinking about that freaking video.
And did an amazing job showing precisely how veritasium's argument is nonsensical
We know
When I was studying Electrical Engineering in the early 1960's we first studied DC and Steady State AC circuits at lower frequencies. Then later we took a class in Transient Circuits and that introduced the concepts of electromagnetic waves and high speed transient effects of electrical conductors, spacing, conductor geometry, electric fields, magnetic fields and high frequency effects on circuits. Then we studied transmission lines, waves and antennas which then lead to Smith Charts and impedance matching and wave lengths, etc. I think what got Vertasium confused was conflating the 'transient' charge effects with the 'steady state' current/energy flow. Certainly an oscilloscope will see a 'pulse' of electric charge after the switch is closed but the light bulb required steady flow of electrons to create an (I^2 x R) energy flow to heat the filament and then create the light energy. Those two events don't happen at the same time. If all we wanted was to create an electromagnetic pulse then our house wiring could use hollow copper wires or 'wave guides' as microwave antennas us to move electromagnetic pulses around the house. However we need electrical energy to continuously flow to light bulbs and move motors, etc. so we must use 12 Gauge wire to move 20 amperes of current in a continuous manner to move energy without overheating the wire as the National Electric Code requires for all houses. The center of the wire as well as the outer part of wire all matter when you are transmitting DC or 60 Hz AC current flow to light bulbs, appliances, motors, etc. Of course if you are transmitting megahertz frequency signals to an antenna then the rules change but that is a different matter as I studied in college. Thanks Kathy for helping clear up the differences in electrical concepts of current flow.
The only difference between AC and DC is whether the current flows through the valence electrons or the conduction band. While the conduction band is closer to the heart of the molecule it is not the "center of the conductor". It is not like the "flow of water in a pipe" that's a blatantly false analogy. Electron drift is from negative to positive. The flow of current is from positive to negative. In the opposite direction. The charge is a virtual photon that pops in and out of existence as the electrons oscillate up and down their respective bands of energy. Most importantly the charge flows in the "holes" left behind the electrons. Not through or in the electrons themselves. That's why plasma physics requires ion's with electron-hole pairs.
@@calinbeale2634i think what everyone keeps getting at is "skin effect" which is frequency dependent depth of conduction. high frequency signaling results in charge density nearer the wire surface.
the switch closure could be considered an impulse, which is all frequencies but the initial edge will likely be the high frequency portion exhibiting the skin effect followed by the quiescent dc state. when you look at the voltage signal on the wavefront it's a step function... high frequency initially followed by zero so the depth of interaction should be increasing with time.
i would posit both components will raise the filament temperature. but the DC component will result in vastly more power dissipation, which makes the light.
I think Derek's imaginary circuit should have had two switches, one on each side of the battery terminals and closes the 2 switches simultaneously to see when the light bulb lights up? Of course, oscilloscope probes place after each switch, may be Veritasium just published the videos for the views only!
@@calinbeale2634 I was under the impression that valence electrons in a metal are already delocalized into a conduction band and that it is these delocalized electrons that are available to flow in a metal wire, either in a consistent direction under a DC electromotive force or in alternating directions under an AC electromotive force. At low frequencies, such as those used in utility grid transmission, I don't believe there is a distinction between the transport mechanisms for electrons through a metal conductor for AC relative to DC. At higher frequencies, we have to consider skin effect, but even then, I believe it is the same "sea" of delocalized electrons that makes conduction possible.
@gracenotes5379 the one thing I would add is that it is not just the conduction band. The CB is a shell for electron orbital closer in to the molecule. The valance band is a lower energy electron band where the "free" electrons float in a cloud. The electron oscillates between these two shells. When it goes up a band it's because it accepted a virtual photon and gained energy. If it goes down a band than it gives off the photon losing energy. It is the passing of virtual photons that is the electromagnetic wave.
Kathy is electrifying and totally awesome! No shock there. She illuminates this topic beautifully. ❤🎉😊
Yeah this video is great. I wish I had science educators teaching me when I was in shool that were half as good as Kathy is at talking about this.
@@WarrenPostma so if we have perfect circle od wire (length 300 000 km, diameter 95541 km ) and we push the switch, will that signal travel just one second ?
Three sentences: Three puns. Three grΩns.
She's a bright spark.
This comment has a high potential to be punny.
This is the peer review process in action. Love it.
No, this wasn't equivalent to peer review, this was equivalent to response papers. Peer review works very badly compared to replications.
@@laurenpinschannelsobviously the veritasium video is already out there. I think this IS an actual example of peer review, in the same way that a response paper would be a form of peer review in the general sense of the phrase.
It is just an example of people creating controversy out of nothing.
In order for there to be peer review, the reviewer must address the subject under discuusion, in this case the Poynting vector. All Kathy does is to profess a dislike for it and for David Jackson who includes a discussion in his book. Kathy claims to be a physicist, but seems unaware of the Poynting vector until the present discussion. I was introduced in my junior E&M course and saw it again in graduate school. The Poynting theorem is simply derived by dotting the E vector into Ampere"s Law and then rearranging to form a conservation law for electric energy. The Poynting vector certainly describes the flow of EM energy through empty space. What is needed here is a discssion of the Poynting vector in dc circuits. Kathy throws up a lot of irrelevant facts but never gets around to the real issue. She does make a glaring error by saying the the electric field is the (negative) gradient of the poential, which is only true in electrostatics. In electrodynamics, one must also have a vector potential to account for the unconservative nature of the electric field due to Faraday's law.
I was one of those electrical engineers that reacted to Veritasium's video in a manner that can be best described as "wait a minute, that explains nothing".
It's true that an electromagnetic wave needs no conductor, but DC current most certainly does.
A lot of debunking of this has been going on since, and lots of good ones at that, so i won't go in to more detail here, but just saying that an explanation with the transmission-line model would have made perfect sense, and that the DC (battery) was a really bad example.
I can see that you have been thinking both long and hard about this, and your result is excellent!
What bugged me most about Veritasium's claim was the headline "electricity doesn't flow in the wire", well how else can you explain DC current?
I'm really looking forward to more of your video's since i find that the historic connection is giving me a firm foothold of understanding, it makes me more grounded, so to speak. (pun intended) :-).
Energy doesn't flow in the wire...
Another EE here. Yes I agree the transmission line model would clarify a lot, and it would explain that the light-bulb mostly likely will slowly ramp up in steps, as you see the reflected wave going back and forth between battery and light, that each have a different impedance than the characteristic impedance of the wire pair. If you look with a scope at the end of a not-terminated T-line you see exactly that. However, the pointing vector does work, even in electrostatics. I applied it myself when I wrote a field simulator (MOM based) to calculate the energy transfer. In this case you need to integrate the pointing vector over a closed surface surrounding the battery or the lightbulb. Voltage is only defined in electro-statics, and doesn’t work well if you have changing magnetic field. When we define voltage for an AC circuit, we use a quasi-static approximation.
Nobody seems to realize that these wire pairs are in fact a networks of resistors and capacitors (transmission lines). Dave and Electroboom get it. But I think this video and Derek's video don't seem to understand it.
@@kriswillems5661 I think Kathy said she had a graduate degree in electrical engineering. If so, she definitely knows what a transmission line is. BTW, you forgot inductor. 😛
@@kriswillems5661Kathy mentions dc circuits, and steady states, but in my non-qualified opinion, the fundamental thing here that closing the switch on this battery / wire / lamp situation creates, for at least an instant, a non-steady state between the two steady states of off and on, and for that intermediate instant this arrangement behaves as an AC system, which is why transmission line theory explains what is going on. Overhead HV transmission lines have a capacitance to ground of several nF/KM, this experiment doesn’t need a light-second’s length of wires to illustrate, electricity leaking away in an AC distribution line is well understood.
Alpha Phoenix just posted a video where he measured voltage at multiple points along a wire. His animation of those voltages wonderfully shows the flow of electricity through a wire after a switch is closed.
Incredible video!
Thank you, that was exactly the video I was thinking about when I posted my comment above about transmission lines. The theory is very well established.
@@philkarn1761which video
This video and Alpha Phoenix's helped me understand the topic. Derek OTOH seemed to try to "bewilder and amaze", for the view count.
@@webherringSadly Derek has become a shill capitalizing on sensationalism.
Veritasium is often off the wall and somewhere out in left field for fake shock effects. People in YT just to grab a mega audience and make money doing so. You rock, Kathy. The truth wins.
Love these videos!. Earlier today, AlphaPhoenix put out a video called "Watch electricity hit a fork in the road at half a billion frames per second" with some interesting observations and visualizations on DC electricity.
That sounds amazing
Funny, I saw alphaPhoenix' video just be for this one.
I just watched about half of the AlphaPhoenix video. He talks more about the flow of information than anything else. That is all pseudo science.
@@davidhomer78because he gives you all the information to follow the scientific method and repat his findings, it wouldn't be pseudo science.
@@Kathy_Loves_Physics It is wonderful. I get lost in the technical explanations, so I'm not sure Alpha Phoenix's video is directly or tangentially relevant to Derrick's video or not, but it seems so.
Part II about Feynman: I believe that he was speaking to religious zealots and other crackpots who are eternal science deniers. He was NOT claiming that you can't explain things to children. I do think you have misinterpreted his words.
in fact feynman was great at breaking things down and simplifying in order to explain them.
He just was opposed to saying that the simplified way is how it works.
When you simplify something in order to explain it, you should say that it's simplified.
@@tommihommi1 I totally agree, that is the point of the Feynman diagrams and the "shut up and calculate" statement, he was always trying to show that the world is strange and wonderful and how things work as opposed to how we understand things work as they can often be mutually exclusive and that is what science is about teasing those two things apart to see what is real.
@Weirdly_wonderful I think I agree with the other commenters, here, about your take on Feynman's quotes which you said were about "education." I don't view the segment that you used about education or about speaking as "handed down from on high," the way you seem to be suggesting in your video. The clip you used was from the beginning of his 1979 University of Auckland lectures describing the theory of quantum electrodynamics (for which he and others shared the Nobel prize).
When viewed in the rest of the context of that video (and especially that segment of his first lecture in the series), my interpretation of what Feynman was describing in that quoted section of video was "I am not going to make a fake analogy to give you some false impression about how this theory works, but because of how crazy the calculations look, or how strange the conception of the models may seem, you may not accept the conclusions we get to draw from this model and conception of how nature works. If you don't like that, you're either welcome to move to another universe where the rules are simpler, or try your hardest to come up with a different explanation and conception that fits what we've observed."
In my view, this just expresses Feynman's personality and general commitment to not taking shortcuts in trying to give explanations for how things work (according to "the human beings who have struggled as hard as they can to understand it"). He says he can't make it simpler, because at that time (and as far as I know, even now) we don't have a simpler conception of how nature works, at that level (explaining quantum electrodynamics). But in my view, it is not a general remark he is making about explaining all of physics or a general remark about the nature of education. Would you agree with that?
Totally agree. Wasn't it Feynman that said "if you can't explain it to a child, then you don't understand it yourself" (or something to that effect)?
So no, I don't agree with Kathy in her view on Feynman.
ps. Seems like it's a quote by Einstein... maybe I just remembered it spoken by Feynman...
Eric L Michelsen touched the right point. I suggest reading Oleg D. Jefimenko’s Electricity and Magnetism, topic 9-5. Displacement Field and Static Charge in Current-Carrying Conductors for clarifications about the static fields in conductors when steady current densities are present.
Jackson’s 1996 paper indicates this when saying: “With the early notable exception of Jefimenko’s book, intermediate or advanced texts are no better”.
This is a very useful comment. Thank you.
Thanks for your interest, Gianmario.
Kathy. I just found your videos. I like learning from passionate women and I like your teaching style. Many thanks.
Another very good response to Veritasium's videos. One of Derek's reasons to make the original video was to spark discussion.
I think you misinterpretted Richard Feyman's comment about keeping it simple.
Einstein once said "God does not play dice" The response was "Eistein, you cannot tell God how to make the rules".
One of Feynman's strengths was, "if at first you don't understand what you are looking at, then don't say physics doesn't make sense. Try looking at it differently till it does ".
Thanks; I was very confused by the Veritasium video which I was never able to digest. AlphaPhoenix just posted a series of videos that made much more sense in which he modeled charge as waves as it moves through wires. It struck me as logical and well presented, and so is a strong recommend.
I think Feynman's quote to be one not about education but one about the scientific community. I like this take quite a lot. To me it's in the same vein as Tyson's "The universe is under no obligation to make sense to you"
Tyson certainly has never made sense of it.
Agree. Feynman was very much in favor of education and explaining and there is much evidence for that view. Here he is pointing out that he's going to be brutally honest in giving an explanation and won't oversimplify it for the listener, which would be dishonest. He says the same when explaining quantum mechanics of light. I love your history lessons Kathy !
Feynman was an elite teacher. He wanted people to understand the concept, not just accept it because a bigshot scientist told them so.
@@fotrj No, he wanted people to accept the concepts of modern physics even if those concepts go against our intuition. If some lay person tells him "time dilation is absurd, your math must be wrong, come back with something better", then he will tell that person to go somewhere else.
I have to go with science, which is why I assiduously follow your channel. You're a hero.
Yeah - there is just one problem. Shinola gets 20Million views and a $100K check from youtube. Science gets 2000 views and lucky if it gets to million.
That's why I don't view the crank channels. Arvin Ash and Sabine are straight-shooters.@@joeboxter3635
@@joeboxter3635true
I thought seriously. about creating lots of new accounts so I could like this video a bunch more times... Kathy, thank you so much, I still have tears on my face because of your kindness and humility, not to mention all of your hard work.
...and I think I can reconcile two of my favorite science educators in my mind. Feynman frequently tried to be dramatic in order to engage his listeners and at heart is a theoretical physicist. Kathy is, at heart, a teacher, and to you, it is the teaching and communicating. Feynman wants the student to already have a complete grasp deep within maths. Kathy, is happy to explain in simpler terms. I like Feynman. I love Kathy. I have Feynman's lectures. I watch and re-watch Kathy's TH-cam stuff to refresh my mind and reeducate myself for all the stuff I forget or forgot. Thank you, Kathy, for making me very happy. Thank you, Richard, for your contributions to science, too.
Exactly. They're really in violent agreement here.
Feynman is happy to explain physics. He does that in his lectures. But he will (very obviously) refuse to bend physics just for the sake of people who reject concepts that contradict their intuition. That was his whole point. It had nothing to do with how to teach physics. Kathy misunderstands Feynman completely on this point.
@@ronald3836 Exactly.
Can't believe we are equating a TH-cam creator to Feynman. It's just laughable.
@@CMHandle That's unfair. Everybody has their contribution to make to education.
I love these historical perspectives!
Much of modern science communication is so difficult exactly because it is unaware of the original progression of discoveries that made us understand these processes in the first place.
I think we should teach most topics by repeating the original discovery, with newer information only added in where they really make it easier to understand.
Well, I made some work about Poynting vector especially in quasi-static cases (in the circuit frame). According to me, there is nothing wrong with the present theories, only a poor understanding of the Poynting theorem I am afraid.
The Poynting theorem doesn't say anything about the actual flow of electrical energy. Worse it gives infinite possibilities to define the energy flow through a vector field, all leading to the same balance. I have shown in one of my articles (published in the AFLB journal), that you may define an energy flow in a capacitor not going outside radially but axially (parallel to the wires) as your intuition suggest, with the same overall balance.
More technically, you can add any rotational field to the Poynting vector without modifying the energy balance. Discussing where the energy flows from one point to another point is pointless :-) both in Maxwell frame and in the QED frame (In the quantum frame, the trajectory of a photon is not more defined).
You may consider the flow of energy in the wire, or outside it like Derek and many others, or in circles as Feynman introduced in its course to illustrate the idea of the indetermination of the energy flow (you should have followed the entire course instead of extracting only a short portion of it !).
If people generally use the cross product definition it is because it is clearer to describe waves propagation in vacuum, and also because its a relativistic invariant, but this is another problem we may discuss another day. The philosophical question about the actual path of electrical energy flow remains open I am afraid !
I'm Eric L Michelsen, but Google is scrambling my name. To clarify, I'm affiliated with the University of California, San Diego (and my last name is spelled "...sen"). There is much interesting and useful material in this video. For example, I have given a talk describing simple experiments which show that power does NOT flow along the Poynting vector, and that is fully compatible with electromagnetic theory. For reference (but not claiming infallibility), I have a BSEE, and a PhD in physics, and decades of experience in laboratories and measurements; I teach this material at the upper-division college level.
However, I think it is well established that the electric field inside a current carrying wire does, indeed, drive the current, and that this field is created by surface charges. Conductors can expel E-fields only in a static (or quasi-static) system. In contrast, a DC circuit is a steady-state dynamic equilibrium, and though the charges in the conductor move to reduce the E-field, the battery is constantly "pulling" them out of (and "pushing" them in) the wire, so they can never cancel the E-field completely. It takes only a tiny E-field in a good conductor to drive a significant current. This is established by extensive experiment, and organized into the detailed theory of electromagnetism (with no deference to anyone's authority).
I have a detailed discussion of the speed of electricity and the Poynting vector in my "Funky Electromagnetic Concepts" (at the bottom of my web page), starting around page 69 (as of this writing). I performed (the moral equivalent of) Derek's experiment, and confirmed that in some very realistic situations (but not all situations), the bulb turns on nearly full brightness, nearly instantly (as expected from theory). My document includes photographs of my setup and results, and a discussion of the theory, but is written at the upper-division college-physics level. This is all well-established science, and fully consistent with relativity. (In Dr. Muller's follow-up video, I think he actually didn't give himself enough credit for his prediction.)
Could you please give us a link to your website?
google for: eric's physics web page
The fact that people are STILL posting responses to that video gives me faith in humanity. I watch them all and every one teaches me something new, a slightly different perspective for thinking of how electricity works. Great one from Kathy here, with an illuminating historical perspective. For all the problems of that original video, hats off to Derek for pushing many of us to look beyond the elementary school depictions of electricity.
Have you seen AlphaPhoenix's recent video? Especially his second channel further explanations about impedence matching? I find it a great explanation as well.
You confused me when you first present Feynman as rejecting the Poynting vector theory, but then state that you reject Feynman's material on the Poynting vector. After checking the Feynman text in its proper context, I noticed that he gives further explanations why it "isn't so terribly puzzling" after all, with the right way of looking at it.
Btw, in the "go somewhere else" video Feynman was NOT saying that some people may just be too dumb to learn physics. He is just criticizing people who have decided to reject stuff like quantum mechanics and relativity because it is "too crazy". Feynman's reply is that if you don't like this crazy stuff, go to a universe where the rules are simpler.
And it mystifies me why you should even consider discounting the physics work of Feynman just because you (falsely) believe you disagree with him on a point of pedagogy.
All in all, this video does not paint you in a very good light at all.
If you listen to Feynman he actually says that the theory (Poynting vector for energy flow radially into a DC carrying wire, etc.) is correct. He further says that our intuition does not match the theory but this is ok.
Poynting (1884) shows that the energy (per unit time) flowing radially into the wire is actually the same as the power given by the much simpler, V*I. V*I is just much easier to calculate than the Poynting vector but it doesn't say anything about where the energy comes from (the E and B fields).
All electromagnetic theory has to be expressed in terms of fields, the 'flow of electrons' is just a sideline. A full treatment would of course use Quantum Electrodynamics whuch brings us back to Feynman 😁
(Melrose's Quantum Plasmadynamics, may be a better jumping off point for someone interested enough to do the full calculation or at least draw the Feynman diagrams).
I've looked at almost all the comments. It seems Kathy doesn't want to respond to critiques that the Poynting vector is correct for DC circuits. She took Feynman out of context. Her rationales for not trusting the Poynting theorem are not strong enough and don't stand up to scrutiny.
Your videos are very informative. Please keep posting on regular basis.
I am a BSChE about ready to retire in 15 mos. Going back to my alma mater to get a degree in physics. Been watching MIT OCW (diff eq to refresh after 40 years) and Elliot and ViaScience... and you... and some others but your videos are fantastic. Thanks Kathy!!!
Love the actual experiments you’ve done! Great channel that I have frequently used before giving lectures to give some human interest to where these equations come from in the first place. Great book too!
I admire your videos. But now, i'm in love into them. You're great communicator and reinventor of old wonders and stories. Thank you for the great work. Looking forward to more videos
Awesome channel. Perfect balance between accuracy, sources worth learning more from, and an engaging presentation. Chapeau!
With dc it's the electric field IN the wire that drive current and power IN wire and ac will be totally different. Sounds like you are correct. Great video. Thank you
What Feynman was saying is that the universe has no need to be simple ---in terms of linear, intuitive to human understanding etc---and that one must accept experimental evidence over a neat simple concise but wrong theory. In terms of his views on education, there were two main sentiments expressed:
1) If you can express something in a way that ordinary people can understand,,then the likelihood is that you don't understand it as well as you think (that's his famous meme on learning)
2) Somethings in nature cannot be explained without first explaining a whole gamut of mathematics except by analogy.
The second sentiment was expressed in an interview where the interviewer had asked him to explain how magnets work and why. Feynman could go only so far before he needed to upgrade the individuals maths skills.
I think that your notion is entirely true in that: anyone should in theory be able to understand anything scientific; however, the depth of understanding does depend upon having or possessing mathematical ideas once you go beyond certain levels of knowledge.
Kathy, I bought your book and wow, so much good dope, kudos! I love history, and electronics has been a hobby of mine since 5th grade! I am self-taught in engineering, as I have no aptitude for a school environment, exams and drinking lectures as if from a fire hose.
Bravo for summarizing the most important elements of disagreement before you even got to the table of contents.
I love your videos, I used to have electronics as a teenage hobby and one of my uncles was working as a microwave electronics consultant in the 1970s here in Australia. I identify with all that you say. Lots of love from David Newton x
Actually, as you well know, Feynman did a a great deal to make physics understandable to people. Who is perfect across all areas at all times in their life.
Right. I don't get the anti-Feynmann slant in this video here, it's quixotic and unexplained.
Honestly, I don’t understand your confusion. I don’t think it’s good for someone to put something that they think is obviously nuts and crazy in a textbook.
Also, I do not know that he did “a great deal to make physics understandable to people”, as I’ve never seen a single example of that.
I’m not asking for perfection, I’m asking for kindness. But I have not watched/ read everything that he did. Maybe he was kind and relatable in other areas. I just haven’t seen them.
Also, we are allowed to have different opinions. I’m allowed to think negative thoughts about Feynman and still be a physicist right?
@@Kathy_Loves_Physics absence of evidence is not evidence of absence. Seeing involves looking. Maybe you have a responsibility to investigate properly, as you do for the characters you write about, before making such a public statement. Feynman did not have the attitude you claim, quite the reverse. Disappointed.
Warren, I am particularly interested in your use of the word quixotic. Quixotic is a reference to one of my favorite novels Don Quixote where a poor farmer decides that he is a knight, and a windmill is a dragon that he cannot defeat.
But I don’t get what that means in reference to my video. I mean, you could be saying that I am not really a physicist, just as Don Quiote was not really a knight. But if that’s the case, then my complaints about Richard Feman are quixotic means that Richard Feinman wasn’t a physicist either, he’s just a windmill.
Care to clarify?
It is hard to separate what Feynman did and what he claimed he did. The guy was an extremely good story teller and had a sizeable ego. That and he had a very poor attitude towards women. Kathy has every right to be suspicious of him, I can only imagine the amount of sexism she has put up with in this field.
I really enjoyed this, and especially your insistence on positivity in the approach, it has given me a lot to think about.
I remember when his first video on this came out and there was a big reaction and discussion to it. I feel it was the perfect educator situation, since it forces someone to really start pondering how all of it works before they can even start to come to some conclusion of their own. In the end, the places where he was wrong seem mainly to be from oversimplifying for pedagogical reasons, and slips of wording that were wrong or make it debatable what was meant, all of which allow for misunderstanding (since I am sure Derek himself understands this, it is more a matter of presentation). It is great that even after all this time, people are still making responses to it, and getting people engaged with the details of how it all works.
When you close the switch, positive charges start to spread on the plus pole, and negative charges start to spread on the negative pole. These charges cause on electric field. On the positive side, with the positive charges, the field pushes away positive charges in the parallel wire, on the negative side the field pushes negative charges away in the parallel wire. So an unbalance is created in the parallel wire and a current flows and the light goes on. This happens after 1/c seconds, because the field only need to travel 1 meter. It's pretty simple, both wire pairs act as capacitors. And DC pulse passes the capacitors (but a continuous DC voltage does not). The continuous flow of current happens only later when the electron flow in the wire starts. This happens much later. So, the bulb flashes after 1/c seconds, but it is only stable much later on.
The electric field inside a wire is only zero when there is no current in it. If it's carrying a current and it has resistance, there will be a charge gradient along it and therefore an electric field.
Thanks Kathy! The world is round again!
Very interesting video. I'm curious if you have seen Nick Lucid's "Science Asylum" video from about 4 years ago titled "Circuit Energy Doesn't Flow the Way You Think" and what your thoughts might be about it.
Great video!!
Im interested if the cucit, but instead treated like a large circle and not two paralell conductors (EMP travel at light speed.)
will this relate back to Cosinus to f ,and electrical motors?
I'm sorry but that's really not how batteries work.
All chemical cells are based on specific redox reactions occurring within them. Some of these do use acids or bases and metal electrodes as their reagents but others do not. Their common element is that half of the reaction (reduction, which consumes electrons) occurs on one electrode and the other half (oxidation, which generates electrons) occurs on the other electrode.
The simplest cells will achieve this by making the electrodes from the reagents, but _there are_ plenty of cases where one, or both electrodes take no part in the reaction. You can keep the electrodes in two different solutions connected via some sort of an ion exchanger. You can cover the electrodes with a catalyst. There are plenty of options.
And second of all, when the battery is not yet part of the circuit, the reaction indeed isn't occurring. But that doesn't mean it can't give you current right away - as soon as you complete the circuit. The reaction isn't progressing precisely because it has progressed the furthest it could get, building up charge on the electrodes, internal wires and the terminals.
And finally, the heat generated from resistance is frankly negligible. The vast majority of heat will be produced in the chemical reaction itself.
I appreciate the time and effort you put into your videos, but my utmost appreciation is towards your tone. I love how measured and thoughtful your videos are. You make the topic very approachable for the newcomer, but also have enough detail and complexity for a well-rounded presentation. Your respectful response to his video is how such videos should be handled.
I agree fully with Feynman's statement. My interpretation of it, based on some wider context, is that he saw simplification as inherently untruthful. He was well documented happily spoon-feeding complex topics to any level of audience. The important semantic detail is that simplification of a complex thing is an arbitrary modification of the thing, and not equal to dividing the thing into manageable components for learning.
Simplifications taught to children are very often a major source of trouble later in their education, and even in general life, because you have constructed a faulty foundation and now the entre first floor needs a complete tear down and rebuild before the second floor can be added. (This applies to any introduction level education, not limited to children.)
In short incomplete (building blocks) and incorrect (simplified) are different things.
A fantastic video. Well presented and very informative. I love the level of detail and how everything is explained. Great stuff! Thank you!
Love this! Finally a "fight" with reason. I'm waiting for Derek's response :)
I hate those "I'm an expert on everything channels" They're usually riddles with false information. I appreciate these kinds of videos
Thank you once more, Kathy........just commenting to tweak the algorithm.
Derek knew exactly what he was doing when he created this passionate debate, catering to the algorithm and justifying it for education.
A shill selling sensationalism? I’m shocked! /s
This is great that we are finally having a discussion about this. I think people think that electricity is like water and flows in the pipes.
It was like engineers arguing with physicists.
In Electronics, we have a number of models and tools to design our gear including
conventional current which is opposite to conventional flow.
As a tech, I was first taught electron flow and regret it to this day.
It’s like learning imperial system instead of metric.
I learned about skin effect in AC but I see there’s a lot more to this than I realize even though
I really don’t need to know it for my daily tasks.
Socratic method of asking and answering questions to arrive at a truth…like the Paper Chase.
I enjoy the deep dive down the rabbit hole to Wonderland by all the creators on this subject.👍
I started as an electronics tech in the Marine Corps, and they taught electron flow. It seemed odd that current would flow against the arrow of a diode symbol. However, that was still the era when vacuum tubes were in use, so there is some sense to talking about electron flow. That school was pretty basic, and raised enough questions in my mind to motivate me to become an electronics engineer.
@@SkyhawkSteve There was... at least some... American profs writing textbooks using electron flow (versus conventional current flow)... but, AFAIK... and apparently... it never caught on. Eventually, I think, everybody promoting electron flow gave up trying to change it.
Electricity, Magnetism, Heat, light / Color, Mass / Weight are different manifestations of Gravity and Continually convert to each other. Gravitational Particles (GPs) move by means of CONDUCTIVITY towards the CENTER of the GRAVITY.
Turbines convert the Gravity Force to Magnetic > Electrical > Heat > Light and everything in between.
When GP moves in the Air (4N1O) Atoms are manifested as Magnetism, therefore Magnetism exists only in the Atmosphere and is absorbed by Compass measured in Air Gap and Magnetic Flux context.
When GP moves in Solid it is observed as Electricity and measured by its Power/Force/Voltage and its Current/Amps and their combination total Quantity of GPs in a unit of time as Wattage.
GPs move at a 90 Degrees Angle relative to their path in [side] Steps, therefore the GPs manifested as Electricity, Magnetism, Heat and Light transit to the Outer Edges of the Medium/Matter.
@@ShonMardani No.
No to what? @@willthecat3861
You’re reminding me of how I learned about ignition coils in high school auto shop. The transformer in an arc welder demonstrates these principles.
Thank you for the video, I unsubbed from Veritasium because Derrick lacks Veritas - he writes too much clickbait, which we already have way too much of.
I think veritasium video mixes two topics, the steady state and the EM pulse.
EM pulse: you have to treat it like a transmission line. It will move some electrons in the light bulb about 1/c seconds later, but not enough to light it up. Bulb will light up only after the signal will be able to "check" the continuity of the whole circuit (otherwise superluminal messaging would be possible).
Regarding the steady state, once all the oscillations of the initial EM pulse have been dampened out: to me it seems only a matter of modeling. The most common model is that of electrons pushed through wires. The moving charges then cause EM (static) fields as a consequence, and, curious coincidence, a Poynting vector appears. But, you could easily say that, lying the conductor in a certain way, you put some constraint on the shape of EM fields, which carry the energy and, as a curious coincidence, electrons in the conductor start to move. Either way, you can't have moving charges without fields and viceversa. Choose the model that fits best, especially, the one that is easier to apply.
My initial comment was blocked (maybe this one won’t be). I would be delighted to debate … but I can do so only through e-mail. Huge respect and admiration from Romania.
I'm only 1:15 in, but I love you already Kathy.
I am not a scientist, but when I first watched the video at Veritasium, I was deeply disappointed by his simplistic approach.
I am reminded of the fact that science progresses because good theories get replaced by better theories.
NOT because of bad theories being replaced by good ones.
It is a process I refer to as "Continual Refinement" and I try to apply that process to myself.
And of course we must understand that Kuhnian paradigm shifts take place in science, and how messy they can be, because science is performed by humans with big egos.
I avoided watching Derek's click-baity piece and the responses for all this time, waiting for your take. AlphaPhoenix's careful measurements are also very fun and clear emperical evidence. You rock.
Congratulations on your book! Cheers...
Shots fired! You're amazing keep it up.
I think energy is just an accounting thing in physics. Energy is defined as the ability of a system to do work. If a system do work then its energy is decreasing, and the energy increases on the other system that the work is done on. This continues until both systems are in equilibrium and neither system can do any work on the other. The physical thing here is work and not energy. Like in accounting, my work is the physical thing and the money I get for it is just an abstract accounting number. So energy doesn't really "flow" as in something physical like water flowing in a river. Something physical must do work. "Energy doesn't flow in wires" is really nonsense, energy doesn't flow. What happens is that a field is created, that field is doing work, pushing the charges, those charges collide with other charges, change the orbitals in the bulb, those orbitals decay releasing a photon (which is also work) and the light bulb lights up. Mass as a form energy comes also from work done. About 99% of mass comes from the complex interactions of quarks and gluons in the proton, which is work. 1% of mass comes from the interaction with the Higgs field, which is also work.
I think this wholly comes down to semantics and what it means to "light up" the bulb. It also seems to have some relationship with the difference between the maximum speed of causality and the propagation speed of "meaningful" events in the physical world.
I give you 2 thumbs up! I don't really understand all things electric but I do have a great fascination with them. When I watched Derick's video on how long it would take to light a bulb I felt uneasy with his explanation although I wouldn't have been able to verbalize it. Your video helped my understanding of my original unease. I also greatly appreciate your definition and comparison of true science vs psudeo-science. Thanks for posting.
The timing on this video is perfect as Alpha Phoenix just released a video about a similar thing, but his explanation of what’s happening felt a bit lacking to me.
As a lay person I've noticed that no matter the subject, a lack of historical perspective can be fatal to clear thinking. I think anyone who wants to study a science needs to retrace the path of those that went before us. Thanks for applying that principle to physics.
Worth noting that "the Jackson" is a well regarded textbook. That's one I've opened in my undergrad studies.
Jackson is THE bible in classical ED. If someone says Jackson is wrong on something, they better be prepared to bring proof.
Yes, it's a masterpiece: written by someone deeply passionate about the subject.
I have your book, Kathy, and I admire it very much. You're doing good work.
You said, "It was because of Feynmann's comments on education that I started discounting all of Feynmann work." This betrays a fundamental principle of science that we look at the science, not the source.
Anti-scientists use this technique. "Oh, he believes in climate change, so I won't take his studies in geology seriously." Feynmann's improtant physics work was peer reviewed. So, you are also discounting peer reviewed science, including I suppose quantum electrodynamics.
I also have to point out that the lecture you showed a clip of was Feynmann at a QED lecture. The audience would be expected to understand his point. Facts (and observations) are the proper test of theory. It was completely irrelevant as to education of children. So, clearly taken out of context.
Real context: In April 1966, Feynman delivered an address to the National Science Teachers Association, in which he suggested how students could be made to think like scientists, be open-minded, curious, and especially, to doubt. (From Wikipedia)
Well, people often make the mistake of confusing the message with the messenger. It's actually a logical fallacy. If you want to attack an argument, attack the argument - not the one who is putting it forward. However, confusing ideology with how the world actually works is often producing this result. Which is a pity, because by very nature any ideology is internally inconsistent.
When I was in college, the professors acknowledged that the electrons flow from - to +, but to keep the math easier, we engineers cleverly came up with hole-flow theory... as an electron moves, it leave a gap, so the one behind that comes in to fill that spot, but it left a hole and the next one behind that moved to fill that gap, and so on. If you look at this gap, or "hole", it is moving from + to -, hence hole-flow theory.
Thanks for Poynting out the mistakes.
Albert Einstein is said to have stated “If you cannot explain your theory to a seven year old, you do not understand it yourself”. I agree that anyone can understand any of the concepts in science if they are properly and concisely presented. I enjoy the presentations on this channel because they are presented so.
Maybe Einstein wasn't right about that. But your later statement is patently false - there are scientific concepts that are outside the reach of some humans. This is true also for me, there are things in science I know I csnnot fully grasp.
Finally someone who explain it. It bothered my mind all these years because it's illogical. As you describe, if we move the switch in any measure, the result will be changed.
All of your videos are a treasure
I'll have to study all these video's to see how it stacks up to what I've been taught and also to adequately know what everyone is posing. Fortunately the subject at hand doesn't make any difference to current carrying capacity as we know it, but is interesting as I have been taught differing things throughout my life. 43 years ago 1980 at high school everything current, field, electron flow all went at the speed of light. As an Electrical technician doing a physics refresher course over a year in 2008 to keep the brain cells firing we were taught the electrical field is created at the speed of light but the electrons themselves move in a sporadic motion as they bounce and collide with atoms in the whole conductor and as such the actual distance travelled along the conductor is very low with out getting into differing variables, voltages etc. I'll have to watch the the original video in question but was confused when Cathy brought static electricity into the video. I love your video's Cathy they are a real treasure.
I thought that in the condition where the bulb is very close to the switch that the bulb would light immediately, similar to the time it would take if the circuit were of small size rather than half way to the moon (or whatever the distance was). I assumed this based on the circuit would be in a steady state prior to closing the switch and there would be a difference of charge potential across the switch, and the charge in the wire on the long end would be constant along it's length. When the switch closes, current begins to flow immediately because of this difference in potential and as the current moves along the wire it continues to provide difference of potential as the charge from the far end of the long wire eventially catches up.
OK maybe I did a poor job of explaining that. It's late and I'm tired. It was fun to think about though.
And no, I don't recall any mention of Poynting Vectors during my education either.
As a Master Electrician and keen viewer of your videos, can you please tell me if you think electrons go forward and backwards in an ac circuit. If so, how far backwards and forward do they travel. I've looked in my text books and spoken to my associates, but no one has a definite proof. Please help , thank you . John M French.
Yes I think you are correct Kathy. Poynting Theory does not distinguish between potential and kinetic energy so flow that seems unphysical will probably be potential energy. With dc there will be energy flow inside the wire.
The Poynting vector itself does not represent energy flow. If you integrate the P. v. around a closed surface, the result is the net energy entering or leaving (depending on sign) the enclosed volume. Alternatively, the divergence of the Poynting vector indicates if a locality is sourcing or sinking electromagnetic energy.
Feynman was addressing the view that the vector itself represents energy flow.
But note that Feynman does agree with the theory which is "obviously nuts". His point is that the theory goes against our intution, but that does not make it wrong (and if you don't like it, then I guess he'd say you can go somewhere else).
Feynman also points out that the practical consequences are near zero, and I very much doubt that it has any real relevance to Derek's question. "Energy" is anyway mostly a bookkeeping device.
@@ronald3836There is this one experiment that you could theoretically do where you measure the gravitational field generated by the energy and energy flux distribution.
However carrying such experiment in a lab is beyond current technological capabilities and as far as I know no one has postulated a way to do it with astronomical observations.
This video was clearly convinced out of ignorance tho, she only ever appeals to intuition and doesn't provide any real argument against poyntings theorem being applicable in a physically meaningful way to DC circuits.
@@marcossidoruk8033 That would be a very interesting experiment indeed.
I guess "energy is just a bookkeeping device" might not sit so well with general relativity. But I do think it is correct to say that we can't help to think about physics in terms of abstractions which the universe itself does not necessarily care about. And of course that is why we do experiments to find out how far our abstractions can take us.
There are these videos about "gravity is not a force", but that presumes that the Newtonian notion of "force" is more than a very helpful abstraction.
You know who's electric? Kathy is electric. You rock!
What a great video. Honest, Respectful and Fearless. In many ways, I hold yourself in the same regard as Sabine Hossenfelder, for whom like yourself I have a special admiration. I should add that similarly I have the upmost respect for Derek Muller who is without doubt a great mind, if (IMO) a tad arrogant, which is a quality I'm not overly fond of.
End of my unsolicited 2 cents. /s:)
Thank you Kathy! I love your videos. "Electricity!"
Derek could've saved himself a lot of grief if he'd just used correct units.
1/c seconds doesn't make sense, it doesn't solve for time.
Without showing where the "1" comes from, the answer appears to be the inverse of c, regardless of the wires proximity.
In units, his answer is 1/(m/s)=m/s, a measure of speed.
If 1meter is used then m/(m/s)=s, a measure of time.
I had the great misfortune of having to useJackson's Classical Electrodynamics book in my graduate classes in the 1970s. It was impenetrable then, and it''s impenetrable now. Like gravity, I think we still don't really understand EM.
I think it's a masterpiece. It's meant to be read chapter by chapter.
@@BarriosGroupieyeah, but so is the bible.. which reads about the same. Lol
Thank you so much for making this. Real, useful power that will turn on and maintain a load takes time to do work.
I agree with your conclusion.
Beautiful: Thank you.
Thank you for the fascinating video. Wondering if we change the switch with the transistor (I guess transistors do not emit emp pulses) will it affect outcome of Veritasium experiment?
Great vlog & explanations! Do you have a video on memristors or Chua's circuit? If so, it would be awesome.
TH-camr Alpha Phoenix just did a pair of absolutely brilliant videos where he tracked the progress of electrical pulses down a twisted pair; it’s by far the best explanation (and demonstration!) of transmission line theory I’ve ever seen. Check them out, I think you’ll find them as interesting as I did!
Has no one ever used an oscilloscope? A scope especially with storage will show the transients and provide an way to measure them. Modern scopes can go well over100MHz and can easily capture nanosecond events. It might also be interesting to use coax instead of bare wire.
I don't think you sounded angry, and I really appreciate your attitude towards education.
You come across like a very nice and reasonable person. ❤
Kathy,thank goodness you are here to keep us right. 😊
She got the basics wrong.
It feels like you are taking Feynman’s comments on the Poynting vector out of context. The Poynting vector is a measure of energy flux, and that’s by definition, there isn’t anything to argue about there. What he was talking about is a bar magnet next to a battery, where no power is either provided or dissipated, but the Poynting vector is non zero, seemingly indicating that energy is flowing in circles, which is not intuitive, but is still true. To say that the Poynting vector doesn’t work at DC, or that it isn’t accurate is wrong, it works because it is defined to work, it is an extension of Maxwell’s equations.
Kathy, I love your work! I have watched all your videos and bought your book. As an electrical engineer (no degree, self taught. As you say, kids can learn anything!) I was quite upset with Derek's video. (I call him my cousin because we have the same last name, but we are unrelated.)
I agree with you that the answer to Derek's video is E) None of the above. As you say, it depends on the characteristics of the light bulb, battery and wires.
The problem is, the long wires going to the Moon, and the opposite direction, form transmission lines. A transmission line can be modeled by inductors in series and capacitors in parallel. As the switch is closed, current instantly flows into the first inductor, and charges the first capacitor. Then it flows from the first capacitor through the second inductor into the second capacitor. The pulse of current and voltage propagates down the transmission line, through each inductor and across each capacitor, until it gets to the other end. Then it reflects back. In reality, there are an infinite number of capacitors and inductors in the transmission line, but the circuit can be simulated by using a finite quantity and still get good results. The point is, the cable has so many picofarads of capacitance per meter, and so many microhenries of inductance per meter. The transmission line has a characteristic impedence, which is determined by the ratio of the capacitance per meter to the inductance per meter.
Let's say you use a coax cable, like my TV antenna does, for the two wires going in opposite directions. The cable on my TV has an impedence of 75 ohms. And let's say the cable has no DC resistance. The transmission line will act just like a resistor with the same 75 ohm impedence, until the reflected pulse comes back from the other end. And let's say the light bulb has an impedence of 150 ohms. So, the instant you close the switch, the battery and switch is in series with the cable going to the left, the lightbulb, and the cable going to the right, for a total impedence of in the cables equal to 150 ohms. Because the light bulb's impedence is also 150 ohms, the voltage across the lightbulb will be 1/2 of the battery voltage, instantly.
Note that the speed of the pulse through the cables is also determined by the inductance and capacitance per meter. That is how Maxwell determined the speed of light from his famous equations. And that is because empty space itself has a capacitance per meter and and inductance per meter. They are called the permittivity and permeability of the vacuum, and they can be measured easily. (Einstein knew that the speed of light in a vacuum is constant, because there is no reason why the measured permittivity and permeability of space should change based on the rate your spaceship was coasting through space. The rest of us had to wait for Michelson and Morley to measure the ether wind and find out there wasn't one.) Note also that space has an impedence too, just like a cable. The impedence of space is about 377 ohms.
Now, what happens when the pulse reflects off the other ends of the long cables? If the ends of the cables were terminated by 75 ohm resistors, the pulse would be totally absorbed. Because the resistance of our cables is 0 ohms, the only resistance in the circuit would be the 75 ohm resistors at the ends of the cables. The light bulb would still see the 150 ohms total resistance, and it would stay half lit.
If the ends of the cables were shorted out, as in Derek's video, the pulse would reflect back and reinforce the voltage pulse going out. When it came back to the bulb, the bulb would see the 0 resistance, then get the full voltage. If the ends of the cables were open circuit, the voltage pulse would be refelected out of phase and cancel the outgoing voltage pulse. When it came back to the bulb, the bulb would see the open circuit ends of the cable and turn off.
The whole story is told by the inductance per meter, capacitance per meter, and impedences of the cables and the bulb. Anything regarding Poynting vectors or fields on the outsides of the cables is not needed. Of course, the properties of inductance and capacitance are due to the magnetic and electric fields around the wires, but once those are understood as bulk properties, the operation of the circuit can be easily explained.
I think Derek was a little disengenuous in this video. There is a quick shot of one of his electrical engineer experts showing him a graph of the step functions in voltage his light bulb would see when the switch was first closed, and when the pulse returned from the ends of the cables. I know Derek is capable of understanding the theory and math, so I presume he kept that part of the story to himself to make it seem more magical than it really is. Derek is a showman, just like all of us to some extent. We have a duty to our audiences to keep our stories interesting!
So, the phenomenon of the transient travelling through transmission lines when the switch is closed is not so mysterious. In your video, you show how sparks from the wires can induce interference in the radio. That is related, because your sparky wires are inducing EM waves into space. But in Derek's circuit, closing the switch is inducing the transient down the transmission line--there won't be any sparks becaue the current is limited by the impedence in the transmission lines. It should also be noted that when the switch is opened and closed, it is no longer a DC circuit. Only after the transients have all settled down can it be analyzed like a DC circuit.
Finally, I just want to say that my favorite video of yours is about Georg Ohm, the guy who discovered Ohm's law. I loved how was proven right, and the pompous Ampere was shown to be wrong. I have used Ohm's law many thousands of times throughout my career, and never realized the rich story behind it. Thank you!
And my favorite Veriassium video is the one on "How Imaginary Numbers Were Invented." More excellent storytelling! I also loved his video on chaos theory "This Equation Will Change How You See The World". True magic needs no enhancement.
5:57 "Static charges do not affect the electric field in a conductor"
That is *remarkably* false. What Michael faraday discovered and whats actually true is that the electric field inside a conductor in electrostatic equilibrium is Zero. The simple reason is that a conductor can be seen to a fair degree of accuracy as a material with free electrons in it, this means that if there was an electric field inside these would feel a force and therefore they would move and that wouldn't be electrostatic equilibrium.
For a conductor that's not in equilibrium this statement is completely false, in fact, for a conductor to not be at equilibrium there MUST be a force moving the electrons inside it. This is such a major mistake it undermines the credibility of the whole video, and not the only such mistake btw.
Yes - it's the confusion between electric statics and electric dynamics.
Re Feynman, as a fellow New Yorker (but uh, not a fellow genius) I think he was just getting at there being a level of irreducible complexity where intuition cannot take you and you have to rely on the math, stated in kind of a sarcastic way. Its ok if you take issue with that, but I don’t think he was insulting children there, just that… like, if you want a 5 year old to understand the path integral formulation of quantum mechanics, the 5 year old will need to be a 6, 7, 8 , 10, 15, 20 year old that learns all the intervening math, and classical physics. Feynman is just saying he can’t do that work for you - thats my interpretation.
Delighted Joy!! Keep em coming. Why wasn’t the resistance in the wire mentioned; perhaps because it is a constant (so long as the material in the wire is homogenous-:)?
They were imagining the wire had zero resistance for this thought experiment.
Thank you very much for doing these well researched video topics with a lot of thought experiments that have been invested in them. Keep this going and take care of yourself. Cheers.