The Big Misconception About Electricity

The Big Misconception About Electricity

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 https://Lutron.com/veritasium

Further analysis of the large circuit is available here: https://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: https://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: https://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: https://youtu.be/C7tQJ42nGno

Sefton, I. M. (2002). Understanding electricity and circuits: What the text books don’t tell you. In Science Teachers’ Workshop. — https://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. — https://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. — https://ve42.co/Muller2012

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

Deno, D. W. (1976). Transmission line fields. IEEE Transactions on Power Apparatus and Systems, 95(5), 1600-1611. — https://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 Iván 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

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39 Responses

  1. Andrew Dotson says:

    And here I thought all vectors were pointing.

  2. The Science Asylum says:

    I made a video about this a few years ago and I can assure you that you _will_ be told by viewers that you’re wrong (even though you aren’t). I’m glad you made the video though. The more of us that cover this topic, the more people we’ll be able to reach and educate.

    • John Collins says:

      @Joel A I think it’s less about ignorance and more about convention of teaching. We learn that current is analogous to a ‘flow’ and that voltage is the pressure of a water tap. The natural association for us to make then is that all these little e- are running down the conductor to their destination. I was fortunate that my HS physics teacher was like “Ya’ll stick out your hand…now stick out your thumb. See the direction that your fingers are curled? MAGNETISM is the real magic here.” That gave me a slightly different understanding and I think that’s really the issue. We have a complex topic of science that we try to teach to children with no other understanding and our analogies just don’t quite hold up.

    • UJason okumhlophe indoda ActsXvii says:

      @Blackfrost273 Industries the Earth Ground is a Vast potential of Negative Charge ‘think of Connecting two batteries in series, if you Center tap the series connected battery if it where 2× 12V lead acid batterys right, if your Center tap is “Neutral” your Positive connection on the battery is + and your negative connection on the battery is – the se applies with the Earth the Earth Ground is a – negative source of energy.

      If you would take a multimeter and put one probe “red” into earth ground and rais the other probe”hlack” into the air and switch your Multimeter to read potential DC you’ll read a Negative DC voltage on earth Ground

    • UJason okumhlophe indoda ActsXvii says:

      @John Collins but here on earth there’s only “ONE” magnetic Pole

      Where all Compasses point toward

      A “South pole”

      The only north poles are the one’s we as humans make, all other Natural magnets are Polarized with a South pole

      Now think about this for a minute

      If a Compass Needle where to be magnetized with both a North and a South pole, and you where thought to believe there’s a North Pole and a South pole, anywhere between the north pole amd the South Pole the Needle won’t move even the slightest because its being pulled by both poles simultaneously and you wouldn’t be able to find your direction, but because there’s only One Magnetic pole on earth the Compass that is magnetized with a North Polarity will always point South towards the Star called Polaris

    • Daniel Thomas says:

      i have watched your vdo! it blew my mind !

    • UJason okumhlophe indoda ActsXvii says:

      @John Collins They say the Magnetic fields of the Earth is Caused by the Core of the earth, that’s real funny because the Core is Molten Iron, and the last time i checked the Curie point for iron is about 700°c so at 4000°c+ there’s no Magnetic fields present in the core of the earth

      As Magnetism loses its strength when being heated

  3. Guy Gordon says:

    A good follow-up question would be “If the field, not the wire, is carrying the energy then why do you need a thicker cable to carry more power?”
    The answer is that you don’t. You only need a heavier cable to carry more Amps, not power. If you increased the power flow by increasing the voltage instead of current you could use the same size wire.

    • Santiago Montero says:

      But if you do that the wire could get so hot that it can melt (that’s the principle of fuses)

    • christopher békési says:

      @Abhishek No, current is the source of electromagnetic fields. Field strength depends on the circuit’s total impedance/resistance where the wire is one part of it. The cable itself does not determine how much energy is being transferred, not one bit.

    • Carlos Falcão says:

      @christopher békési misunderstood your comment sorry

    • Larry P says:

      Due to the resistance of the wire, the electric field is not exactly perpendicular to the surface of the wire, so the Poynting vector points slightly into the wire, supplying the energy that heats the wire.

    • Adrian Wilson says:

      You assuming what’s going on in the wire affects the field. What if it’s the field affecting the wire. Think of the field carrying the power also effecting the wire so you need a wire hefty enough to dissipate the waste heat. Also no real wire is 0 resistance so all normal wire is also a energy sink.

  4. Carl Corey says:

    If you emphasized the “Lightbulb has to turn on immediately when current passes through it” part by saying “any current passes though it” and making clear the fact that this is very necessary for this thought experiment to work at all, not as a simplifying assumptions for sake of experiment, less people would argue with you. Also, that part is the actually necessary part of the experiment. It actually would have worked with normal resistive wire too. Emphasizing the resistive wire was a major red herring because it makes it sound like some reasonably large amount of energy has to be transferred before the light turns on, not that the light turns on at any non zero energy though it.

    • bmw123ck says:

      @The idiot said: Yes! That is why, to bring electric power over long distances the voltage is increased. P=V*I, for the same power, the more you increase the voltage, the less current flows, and thus the losses on wire resistance (Pwr=I^2*R) are minimized. Note: “I” is the same in both equations.

    • PleaseDontWatchThese says:

      Thanks your comment helped. Basically just saying electromagnetic does not need a medium like how a transformer works.

    • Carl Corey says:

      @The idiot said: There would be voltage drop, but no amount of voltage drop other than infinite would cause the bulb to not turn on by the assumption given in the video. If there is even a minuscule, undetectable by current technology, level of current flowing though that bulb, it would turn on by the assumptions given, and as long as the conductors are conductive by any amount other than 0, and the rest of the world is less conductive in a significant amount compared to the conductor, the bulb will still turn on in very small fraction of 1 second.

    • Gustavo T B dos Santos says:

      ​@The idiot said: resistance increase with distance and decreases with width (more larger decrease resistance)
      more longer increase resistance​ ,
      every material have some resistance but the point was about how it flow in eletromagnetic field

    • Carl Corey says:

      @PleaseDontWatchThese Yeah, exactly. In my understanding, the experiment is sort of acting like a transformer unwound in to a straight line until around 1 second mark ish (I think it depends on conductors and other stuff but I don’t feel like digging though simulation software)

  5. windgrins says:

    I’m an electrical engineer and I’m not really sure this is the correct answer although I could be wrong. Forget light bulbs and just use a 100 meter wire and a time interval counter with the time interval measurement across two sampling resistors (one close to the source and the other at the end of the line) (since a conventional bulb is just a resistor). I’m pretty sure the signal has to propagate all the way through the 100 meters of wire to have the current flow across the second resistor to produce the measured signal in that device. Otherwise how would TDR (Time domain Reflectometers) work which measure the length of time that a signal takes to get to a discontinuity in a line?

    A really explosive test of this was the nuclear fission plutonium bomb! Each segment of High Explosive surrounding the core had to have matched delay lines to bring the firing signal to each segment at the same time to get a uniform implosion to compress the plutonium to fission. If the energy of the detonator circuit just went through space, how did the segments on the far side of the bomb from the detonator (which were further away from the trigger source) get a correctly timed (and not delayed) signal?

    I really think you need to test this theory out with real world measurement devices because this sounds all wrong and your eyeball and an LED is not going to measure properly any reasonable length of wire. A good Time interval counter can make this measurement easily and you don’t need the light second of wire. Just scale the results appropriately for 1 meter of separation of battery and source and 100 meters of wire to the load and I’ll be easily convinced.

    I’m guessing that it is the propagation time of the fields through the line even though the Poynting vector is correct in terms of energy magnitude but it is not giving you the time information. I have no issue that the energy is in the fields but I think the value of the local field is going to be from the conductor, not the intervening space. There may be an issue if the conductors are radiating into space but a shielded conductor for a turn on transient will only carry the signal at the normal speed of the conductor. The issue of reflection changing the value of the current is a different issue but that also reflects signal propagation time through the conductor.

    I really don’t think you have interpreted the professor’s statements correctly in regards to this problem but I’m happy to learn differently.

    • bmw123ck says:

      I am an electric engineer and I just need him to rephrase all electric theory usig thjs concept of the power transmitted by the fields… You still need the wires to propagate the fields in the direction you want them to propagate. The wire still plays the major rol transmitting the energy downstream.
      I suppose then that resistance can be then redifined as the “non-uniformity” of the fields around the wire.
      I’m starting to think about this as a change in perspective and not a completely game changer.
      Yes wires do radiate EM but, the most part is kept close to the wire, otherwise electric arcs would be all over the place…
      To sum up, I think the hughest mistake on the video is not making any reference at magnitudes of energy transmitted in every direction

    • brendon wood says:

      The problem is in the definition of lit. Technically at the point you turn on the switch there is a current spike and that will capacitively/inductively couple to the lightbulb on the other side causing it to experience a flow of electricity. This would happen to another identical bulb that was not in the same circuit though so is not a particularly useful or illustrative example to explain the actual concept in a helpful way.
      They are “technically correct” which I believe is the best kind…

    • Peter Warasila says:

      I am also unconvinced by his explanation- but not of the result. 1/c (ish, since it not a vacuum) makes sense for how long it takes to see some effect, but clearly not steady state.

      I’m not sure how much high speed PCB design you’ve done but I’m rationalizing it as similar to return current under a trace that has a step function propagating down it and it makes sense that there would be effects from the field nearly instantly across 1m.

      This explanation is *not* good though. Definitely doesn’t get across the true idea that the energy is in the field effectively. There are other demonstrations which are easier to see and rationalize the results from.

    • The Wizard says:

      @Jesse nyffenegger Nice try North Korean Dictator Kim Jong… _Yo?_ (What letter are we on now… 🤔)

      “Remember Kids, ‘Loose Lips Sink Ships.” 🙊

      “Always ask your Wholesome American Parents before you never talk about how you were taught to make even the most outdated, rudimentary, and elementary school level WMD’s in the YouTube Kids Comment Section.” 😉

    • rev.c.russell says:

      @Jesse nyffenegger Definitely electrical signals in the bombs. They used very precise vacuum tubes.

  6. Josh Barclay says:

    As an electronics technician (radar, radios, antenna systems, etc.) this was very enlightening. Thank you for this. I will definitely be watching this again. Studying how electronics work is a continual process for me.

  7. Coolaid says:

    What I still don’t understand is this scenario: What would happen if there was an additional light placed at the 0.5 Lightyear mark (where the cable turns around), and the original light was 0.25 light years below the battery instead of 1m as shown. Which light would turn on first?

  8. Zeek says:

    *_Use this one simple physics trick that the power companies don’t want you to know._*

    This is why you can pull electricity out of the air near any power line; the magnetic fields extend much further than even the base of the posts.
    _(Also don’t actually siphon from power lines, people have been sued for theft, even though it’s leakage.)_

    • Parvesh Khatri says:

      My village has 765000 volts AC power line going, and one place is high enough to go with 10 meters to the wires. When I stand there, my body hairs stands up. And when I lift one of my hands up and touch any person sitting below on ground, we feel a zapp

    • Le Rui says:

      Isn’t it because all things conduct, it’s just that air is one of the worst ones, and once you get too close to a power line, the high voltage makes the “circuit” work like a capacitor? Don’t judge me, I’m taking electrical engineering and I just decided to make my life harder by watching a video that tells me it’s all lies :p

  9. hardstylaz101 says:

    I’ve solved hundreds if not thousands of electrical questions, but this video and concept absolutely blew my mind. Thank you once again for the excellent video!

  10. Jaime says:

    This does not explain why some metals – copper, gold, silver – are better conductors than other metals. Care to explain? Thanks for the (always) excellent presentation.

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