The Big Misconception About Electricity

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Published 2021-11-19
The misconception is that electrons carry potential energy around a complete conducting loop, transferring their energy to the load. This video was sponsored by Caséta by Lutron. Learn more at Lutron.com/veritasium

Further analysis of the large circuit is available here: ve42.co/bigcircuit

Special thanks to Dr Geraint Lewis for bringing up this question in the first place and discussing it with us. Check out his and Dr Chris Ferrie’s new book here: ve42.co/Universe2021

Special thanks to Dr Robert Olsen for his expertise. He quite literally wrote the book on transmission lines, which you can find here: ve42.co/Olsen2018

Special thanks to Dr Richard Abbott for running a real-life experiment to test the model.

Huge thanks to all of the experts we talked to for this video -- Dr Karl Berggren, Dr Bruce Hunt, Dr Paul Stanley, Dr Joe Steinmeyer, Ian Sefton, and Dr David G Vallancourt.

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References:
A great video about the Poynting vector by the Science Asylum:    • Circuit Energy doesn't FLOW the way y...  

Sefton, I. M. (2002). Understanding electricity and circuits: What the text books don’t tell you. In Science Teachers’ Workshop. -- ve42.co/Sefton

Feynman, R. P., Leighton, R. B., & Sands, M. (1965). The feynman lectures on physics; vol. Ii, chapter 27. American Journal of Physics, 33(9), 750-752. -- ve42.co/Feynman27

Hunt, B. J. (2005). The Maxwellians. Cornell University Press.

Müller, R. (2012). A semiquantitative treatment of surface charges in DC circuits. American Journal of Physics, 80(9), 782-788. -- ve42.co/Muller2012

Galili, I., & Goihbarg, E. (2005). Energy transfer in electrical circuits: A qualitative account. American journal of physics, 73(2), 141-144. -- ve42.co/Galili2004

Deno, D. W. (1976). Transmission line fields. IEEE Transactions on Power Apparatus and Systems, 95(5), 1600-1611. -- ve42.co/Deno76

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Special thanks to Patreon supporters: Luis Felipe, Anton Ragin, Paul Peijzel, S S, Benedikt Heinen, Diffbot, Micah Mangione, Juan Benet, Ruslan Khroma, Richard Sundvall, Lee Redden, Sam Lutfi, MJP, Gnare, Nick DiCandilo, Dave Kircher, Edward Larsen, Burt Humburg, Blake Byers, Dumky, Mike Tung, Evgeny Skvortsov, Meekay, Ismail Öncü Usta, Crated Comments, Anna, Mac Malkawi, Michael Schneider, Oleksii Leonov, Jim Osmun, Tyson McDowell, Ludovic Robillard, Jim buckmaster, fanime96, Ruslan Khroma, Robert Blum, Vincent, Marinus Kuivenhoven, Alfred Wallace, Arjun Chakroborty, Joar Wandborg, Clayton Greenwell, Michael Krugman, Cy 'kkm' K'Nelson,Ron Neal


Written by Derek Muller and Petr Lebedev
Animation by Mike Radjabov and Ivy Tello
Filmed by Derek Muller and Emily Zhang
Footage of the sun by Raquel Nuno
Edited by Derek Muller
Additional video supplied by Getty Images
Music from Epidemic Sound
Produced by Derek Muller, Petr Lebedev and Emily Zhang

All Comments (21)
  • @hdezoo
    I’m so glad this video exists. I use to completely not even understand how electricity worked, and now I still don’t.
  • @ElectroBOOM
    Well well well, stepping into my territory, eh?! I shall make a video about this!!
  • @coconutmilch2351
    when i lived on land like a normal person, i never thought about this stuff. now that i live on a sailboat, i'm obsessed with how absolutely "normal" things work and electricity is my favorite topic because it's so MYSTERIOUS!!! i loved this video :D
  • @YThome7
    Very interesting. You brought me back to my years at the ninth grade at high school when I asked myself this question and made some reasonable guesses. I wish I had a teacher like you. By strange coincidence on my entry exams to Moscow University I had to explain electromagnetic induction and during rather detailed examination a professor asked me about behavior of electrons in a conductor. I presented my "reasonable guesses". Those days exams were blind - they didn't know anything about me. But the professor smiled: "You are not from a big city?" I said, "No, I'm from Ukrainian provincial town". "Did you read a book by Zhdanov recommended as an extra material for AP physics?" I said, "No, there were no such a book in our library". He smiled again: "So you figure out yourself". I got A and was accepted.
  • @DeSinc
    but wait.. how can that be possible? what if someone cut the wire at the end and then at the same time you turn it on? does it still turn on instantly, but then "realises" 1 second later that the wire got cut and turns off again? I guess from your perspective, you would be turning it on first, and then from your frame of reference you would PERCEIVE the other person cutting the wire only 1 second later, despite them doing it a second earlier from their frame of reference.. edit: but what about signal reflections? what are they then? what the heck was I dealing with with ADSL ports having the signal reflected back to the first wall socket from the disconnected wire leading to the 2nd wall socket? and why do RAM traces on motherboards suffer from reflection?
  • As an electrical engineer and faculty, I knew it but never told students. The charges do not flow. It is electromagnetic energy transfer as explained here.
  • @paradossoDFermi
    There seem to be two distinct claims here: 1. the energy from power plants to homes is carried by EM field around wires, which I find clear. 2. But, if a bulb is 1m from a battery and the wires are much longer, the time for the switch signal to reach the bulb depends on the battery-bulb distance only and takes just (1 meter/c) seconds, irrespectively to wires' length. Wires are necessary (putting a bulb near a battery does not light it up without wires); however, their length seem irrelevant for the system's response. This seems to give a superluminal signal speed for any wire longer than 1 meter?
  • @dylandailey3191
    EE here; I think most of this info is technically correct, but potentially misleading in some areas. For one, while it's true that energy is transferred in the space around a conductor, as opposed to through the conductor, the vast majority of that transfer is taking place extremely close to the conductor (we're talking millimeters, typically), due to both the magnetic and electric field strengths decreasing exponentially with distance from the conductor. So in reality, the energy being transferred actually decreases superexponentially with distance from the conductor. Now, in power lines, the ground is still a concern because it's a very long conductor, carrying very high voltage, at very high currents; it's a somewhat extreme case. Yet, even though the cable is miles long, we only need to separate it from the ground by tens of meters to significantly reduce losses over that long distance. Furthermore, the ground is only a problem because power lines are AC. If they were DC, you could lay the cable right on the ground, and you wouldn't get any significant energy loss. Edit: see below, the dropoff is not actually superexponential, but the general idea that energy transfer is greater closer to the conductor is still accurate. For two, the analogy of electron flow being like water through a tube is actually still accurate in the case of the undersea transmission line. The metal rings around the cable cause a change in electrical impedance for that section of the cable. In the case of water in a tube, this would be analogous to having an air bubble trapped in your tube. As a pressure wave travels through the water, it will suddenly hit this air pocket, which is far more compressible than the water (i.e. has a different impedance), which will cause the waveform to distort in precisely the same manner as the electric wave does in the cable. Some energy will pass through the bubble, creating your distorted (attenuated) waveform, and the rest of the energy will actually become a wave reflected back in the other direction. This is precisely what's causing the distortions in the undersea transmission line. There's a bunch of reflected waves bounding back and forth between all the iron rings that stretch and distort the original signal. (for the real electrical nerds, check out "time domain reflectometry", which uses this principle to precisely detect where a fault exists on a power line) Third; yes, energy transfer from the switch to the bulb will occur in 1/c time (by the way, I think you could clarify this by representing it as d/c time, where d is distance from the switch to the bulb. You never really state where the 1 comes from in that equation (at first I thought you were implying it was a constant value, unrelated to this distance)). And yes, you do clarify that it will only be a fraction of the steady state energy. But I think you should stress that this would be an extremely small portion of that steady state energy. The initial energy that the bulb receives will only be due to the capacitive and magnetic coupling between the two long portions of the conductor. And in the case of wire separated by 1 meter, both the capacitive and magnetic coupling would be practically zero. This again is due in part to the exponentially decaying electrical and magnetic field strengths with distance from the conductor, as well as the poor electric and magnetic permiativity of the dielectric (air) between the conductors. Fourth; addressing your question about "why is energy transferred during one half cycle, but not returned back to the plant in the other half of the cycle", I think your physical demonstration actually explains that perfectly. No matter which end of the chain you pull, there's something down the line offering resistance to the motion of the chain. Heck, you even get friction between the chain and the tube, which is like resistance in electrical conductors. However, if you attached a sort of clock spring to your wheel (such that the spring always worked to return the wheel to its at-rest position), you would indeed see some energy returned to the power plant (you) on the second half of the cycle. This is analogous to powering a capacitive load with AC.
  • @besmart
    I feel like a baby who just realized mom and dad don’t really disappear during peek-a-boo
  • @JamesSmith-ig7gw
    Had I thought about it more than a half second, I would have gotten it right, but for the wrong reason. 😂 I answered D. None of the above, believing the light to come on nearly instantaneously, but C. 1/c IS nearly instantaneously. I, too, was taught(and very much under the impression) that it was the movement of the electrons that "powered" the device, so that it doesn't matter how many you have stacked in line, the moment you push/pull the first, the movement travelled through each one instantaneously. I'm glad that I now know how electricity is actually transferred! Thank you!
  • @TheLeftistOwl
    The thing about this explanation is that it makes so much sense when you consider how you can tap into electronics without ever physically plugging into them. You can hijack the RF frequencies emitted and recreate what's the displayed by the device. This is why the government has a specially designed devices that are made to trap those emissions and prevent signals from penetrating.
  • I teach physics at the University of California, San Diego, including this very topic. Within an hour of watching this, I set up the experiment, and got the result. I have photographs of the experimental setup, and of the oscilloscope traces. I discussed the results at length with a physics professor friend, and we agree on the explanation. In fact, the load gets (nearly) the full voltage (almost) immediately; there is no (visible) ramp-up time, nor delay through the long wires (delay < 10 ns). This is fully consistent with transmission line theory that is well established for about a century. Dr. Muller's Veritasium series is great, but in this case, there are several claims that are incorrect, or at least misleading. There are many subtleties, and I cannot do them justice in a comment. I would enjoy talking with Dr. Muller to clear these up. For reference, I have a BS in Electrical Engineering, a PhD in physics, and I am author of "Quirky Quantum Concepts", an upper-division/graduate quantum mechanics text supplement. This is my first Youtube comment ever. Update: I love the Veritasium series, and I have learned a lot from it. To respond to some replies: I chose the simplest case, which I think illustrates the point that power can reach the load without going the whole length of the "wings." The analysis link below the video covers the more-complicated case. My "wings" are 50' hardware store extension cords. My propagation test confirms that coiling them doesn't matter, as expected. My analysis is fully transient, and the circuit transits to steady-state DC over time. Resistance can safely be approximated as zero, but inductance and capacitance cannot, as expected by theory. My load is 270 ohm, roughly the on-resistance of a 50 W incandescent bulb. The characteristic impedance Z ~53 ohm, which is substantially less than the load; that's what's needed for the simple case of near full response nearly immediately (the load is not matched to Z). In this case, the wing capacitance dominates the behavior. Consolidating my previous reply: Examples of subtleties: Do two electrons repel each other? (a) Most people would say yes, and I agree. But one could argue (b) No, one electron creates an electric field, and that field pushes on the other electron. This is also correct; it's slightly more detailed, and from a somewhat different viewpoint, but (a) is still correct, as well. But (c) In calculating the force of (b), we use only the E-field from one electron, even though we know both produce E-fields. To use the full E-field, we have to compute force with the Maxwell stress tensor; this is also correct. There are multiple correct views one can take. The video's chain analogy is very good, and correct. Separately, a few replies have hit on the most-direct (IMO) explanation: the capacitance in the wires provides an immediate, physically short path for the electricity to reach the load. The path of current changes over time. Your gut might tell you that the capacitance is too small, but a quantitative transient analysis using standard circuit theory matches the experiment. Special Relativity still stands. More subtleties: characteristic impedance, etc. I do similar demonstrations in class, so I happen to have all the equipment and experience ready to go.
  • @MattMGK
    After watching this video I can confidently say I understand less about how electricity works than I did before.
  • @pff1974
    I love the field and poynting vector visuals in this video, makes understanding the direction of energy flow clear.
  • @ramontan7620
    Until I saw this video, I was of the [flawed] understanding that electrons are responsible for the work done. My education gave me the [wrong] impression that because current flows through a conductor, then it must be the electrons in the current that are "doing the work". Where else could it be? The mechanical analogues with water tanks also added to the incorrect understanding. I could (and should) have also convinced myself that Work = Energy, and that current or charge are NOT units of work, so it has to come from somewhere else. But why is something that is so fundamental to a student's learning not explicitly stated in lectures and textbooks? Thank You Veritasium and the author, for this excellent and enlightening video. And may our teachers and writers of textbooks also take note.
  • I'm 66 years old. As a child, we lived near large transmission lines in a rural area of CA. They passed over one of our pastures. We had a small water pump shed near the base of one of the towers. I "helped" my dad bury the power wires to the pump shed, 400 ft. from our barn/shop when he was installing a new pump. My dad used pipe strapping tape to mount some fluorescent tubes inside and outside of the shed. Everynight the lights were always on and I asked him why. He took me out to the shed, and asked me if I felt anyything... I realized that the hairs on my arms felt tingly, and I felt something in my ears. He explained about how such high voltage cables as above "induce" a magnetic field way around the big cables, that's what gives me the feelings, and what makes the tubes glow like they were wired to something. That had to have been 1960 /61- as I had just started 1st grade. He drew some sketches to show how "he thought" it worked. He gave me a basic electricity book and quizzed me every once in awhile. His sketches looked just like your graphics. I guess my dad WAS a lot smarter when I was younger. LOL
  • Of course I find this video now… around 6 months ago I got into a small debate with my electrical engineering professor over a topic very similar to this. Everyone in the class seemed to be on the professors side which I guess makes sense but then the following week our professor walks into class and tells me he thought about what I was asking and had looked into it. He walked up to the board and showed some of the similar stuff you did in this video and proclaimed I had actually been correct and my original question that countered his previous discussion he admitted to the class he was in fact wrong. This was the first time in my life I had such a crystallized idea of what someone that was truly intelligent acted like. He wasn’t upset, frustrated or hurt that his initial statement was wrong because he didn’t care about being right, he cared about the truth. I know it sounds corny to say seeing someone look for confirmation instead of affirmation changed my outlook on life but it really did. Never before had I seen some so openly question their very own view and search for the truth rather than search for what backs up their view or idea. Great video, as always
  • @junlee7293
    Best explanation on energy from electricity I've encountered, especially ac vs dc
  • @Eden-is-Here
    This makes so much more sense than the model taught in schools.