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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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
Does it mean it takes 1s to light up if the wires are shielded?
A little more love for Heaviside is requested 😉 He reformulated Maxwell’s equations to what we use nowadays which is a central point about knowing-not-knowing something we use everyday. Thanks for the vid, interesting.
OK. So here is my summary more thought out. The answer is B and D ( sort of). Other people are assuming the only way the energy can transfer from the battery to the light bulb in 1m/c seconds is thru magnetic induction or capacitive coupling thru the wires in close proximity of the battery and the light bulb.
1. Capacitive coupling. Since the Battery is a DC source, the only induced current via capacitive coupling will occur right at the time the switch is turned on and there is a transient (t = 0). However, after the switch is thrown (t > 0), the source is DC and the capacitance will act as an open circuit. So there will only be a brief blip of capacitively induced current to the light bulb. However, it won’t be sustained.
2. The scenario that Veratasium shows is a two parallel wire pretty much infinitely long. So you can use Ampere’s Law to determine the B field and force on the wire with the light bulb with respect to the current running thru the wire at the battery. I = (1/mo)*(B*2*pie*r). The B field that the wire that the bulb is on is inversely proportional to the distance between the wires. In this case is 1 meter. So it is safe to assume that the induced current in the wire at the bulb will be much less than the current that is occurring in the wire at the source. So if the bulb does blink at 1m/c seconds it will be very fast and very weak.
The only time the bulb will light up for a sustained amount of time will be after 1 second when the E field travels the entire light seconds around the circuit at 1/2 light meters second away. So the answer is B. But maybe D sort of.
Thinking 1 second. Time for signal to reach lightbulb
None of the above
e
Electrons "tend" to flow on the outside of a conductor. This is why stranded cables have more capacity than solid conductors of the same size.
I don’t think I’ll ever understand electricity
If the power travels along the outside of the wire and not in the wire, why do multimeters not detect current anywhere except in the wire?
.5 seconds
You’d have to be an (vaxxed) idiot to give Alexa ANY control over anything in your home…
D
Hello, could you explain what would happen if in the example you were giving the battery and the bulb are the ones separated by the distance of the 1 light second?(so instead of them being 1 meter apart they are both in space opposite of each other from earth)
A
I remember what a genius scientist said about that he could turn on a light remotely without using a cable, and finally i found out how the teory of that he does it
so if you put the battery and the light bulb each in a Faradays cage, would the light bulb be as bright as if it was not in a Faradays cage? All other things left the same of course, and with holes through the Faradays cages for the cables.
Here I am, writing my answer to the question after the video, but also asking my own: Why would I lie and say I knew what was really going on? First of all, I think it’s very fair for me to answer what I have been taught. That being answer *B* , by the way.
Second of all, I would not be watching this, if I already knew the answer. Or if it was answer B, I’d be calling you out for clickbaiting me with a title like "The big misconception about electricity". So no, you’d better prove what I have been taught, was in fact wrong. xD
2s
The light should light up immediately when power is applied through the light year length wire because of quantum nonlocality.
So, the light itself and the electron are not working the same way,? The "speed of light" but then what is it. The speed of the matters limit of what we are made also.
but doesn’t that mean, switching on the lamp, it happens faster than lightspeed?
1/cs
edit: fascinating video!
E none of the above i guess cuz why not
E
This is a great experiment that has many phenomena wrapped into it. Unfortunately, I can’t cover them all, but will try to hit some high points.
Fundamentally, the experiment uses lumped circuit elements to illustrate an electromagnetic effect. This is likely the point of confusion for a number of the comments. So let’s be clear about a few things. The Poynting vector (represents instantaneous electromagnetic power flow) is zero before the switch is closed. Immediately after the switch is closed, a transient electromagnetic field is established b/c electrons in the wire begin to move—creating a magnetic field. At this instant a non-zero Poynting vector is established emanating from the battery and sections of the wire causally connected to to the battery. This Poynting vector is mostly bound to the wire (ie the wire provides a preferred path for the electromagnetic energy to flow). So electromagnetic power flows primarily down the wire to the light bulb. However, the Poynting vector is NOT completely bound to the wire. It has components in all directions—even though it is exponentially attenuated (ie, it is said to be evanescent) in most directions. In fact, a component of the Poynting vector flows from the battery (a lumped circuit element) directly to the bulb (an lumped circuit element). However, that component will be quite small (and depends on the distance between the battery and the light bulb) b/c the electromagnetic energy that flows directly from the battery to the light bulb does so through an evanescent electromagnetic field.
The resistance of the wire must be understood b/c the wire’s resistance will dissipate energy from the battery through Joule heating (btw, the energy that goes into Joule heating is energy lost forever, ie, it is not conserved). If the wire is resistive and too long, then no energy will effectively reach the light bulb by traveling down the wire b/c Joule heating will remove energy from the electromagnetic field (attenuating the Poynting vector) traveling down the wire. So, if the wire ran around the moon and back, then the light bulb would not turn-on when the switch is closed unless the “battery region” of the circuit is sufficiently (inductively) coupled to the “light-bulb region” of the circuit to stimulate the light bulb.
Here is the key to correctly understanding this experiment. The Poynting vector AT THE light bulb has many components coming from all directions. The largest component arrives by traveling down the wire (as long as it’s resistance is not too large). Now, the component of the Poynting vector large enough to stimulate the light bulb will establish the time delay from switch-closing to bulb-lighting. But that time delay cannot be less than that for the speed of light travel-time along a direct path from the battery to the light bulb.
This type of experiment is notoriously dependent on it’s GEOMETRIC layout to fully understand all relevant phenomena.
Very misleading video
So… What about shielding…? It is vaguely refered to when talking about first undersea telegraph cable, but not really followed up. What if the wires/battery were shielded…? Would the result be the same?
Why didn´t you say in your video explicitly, that the almost immediate turning up of the light bulb has nothing to do with the giant 600.000 km wired circuit? It would work even if you cut the wires a few meters from the battery, because it is caused by something else than the wired circuit 🙂 But I like your videos anyway…
Wow
I have tons of questions right now:
*If the electrons aren’t the ones that flow through the wires, and are not the ones that power devices through their movement (Their current), but is the Electromagnetic fields that get to the device we wish to power, Then why do resistances affect the power transmitted to the device, when the only thing that transmits the power is the fields? How can resistance affects the fields?
*If electrons don’t move through the wire, then from where it comes the electromagnetic fields if there is almost no movement in the electrons? This including that the way electromagnetic fields are formed (In electricity) is through the movement of charges according to "The misconception"?
*If electrons don’t move, then how is it possible that a body positive charged, recieves charges from a negative charged body? This could even include lightning, how is it possible that a cloud negative charged releases charges to the earth, if the electrons cannot move from the cloud to earth?
E
A wire with NO resistance is not possible and such a super conductor is not possible… so this is a TRICK question and the answer is a dis-credit to science, in general. It will give you the correct answer for an IMPOSSIBLE situation and the WRONG answer for reality. Their is no "field" until there is a circuit. The area around the poles of the battery will extend their field about the distance of a nano metre, at most. It takes 2,000 volts for an electron to jump one foot in dry air.
No Way!!!…
E
Moral of the story: don’t live under high voltage power lines, or if you do, don’t be moist, or if you are moist, don’t touch any ground.
😉
I think you’re probably wrong. A wire is a waveguide that will lead a wave of energy along the wire. Unless you get some coupling between the wires, but i dont think that was the point of your video. Since you’re using dc, the wave is a tsunami that doesn’t end until you flip the switch
D
Experimental design: I think we can test this with modest hardware. I”ll propose that a single-ended example is sufficient.
1) make a simple ring-oscillator from cmos inverting line drivers, with a ~500 ohm bulk (carbon) resistor load to ground.
2) measure the frequency.
3) insert 75m of UTP twisted pair into the circuit; w/ two ends between the last driver and the resistor, and the other ends shorted.
4) measure the frequency again.
A 3 inverter cmos ring oscillator w/ 10ns gate delay might oscillate ~1/(2*3*10ns) or 16.6Mhz. [expected result for 2) above]
Veritasium argues that the added time delay in case 4) is just the 1mm between the twisted pair divided by c or 3.3 picoseconds.
The resulting frequency would drop to ~1/(2*(3*10ns + 0.0033ns)) , so just ~2khz below the 16.6Mhz at 2).
I argue that the insertion of the UTP will cause a delay of 2*75m / c = 500ns. To the oscillator frequency should drop to ~1/(2*(3*10ns + 500ns)) or 0.944Mhz. [note the delay is likely ~750ns due to the lower velocity factor in UTP, So maybe 640kHz is more realistic.]
It won’t take much instrumentation to see the difference between 16Mhz vs 1 Mhz.
Actually, that makes sense: We own a stove with an electrical clicker, and we also have a stereo device, and when you use the clicker while the stereo is on it cuts, it may be because the spark messes with the electrical field of the thing and causes it to jitter.
Ugh, I know science isn’t intuitive but I now have a massive headache after that one. And now I’m afraid to turn on the lights……
E. None of the above.
The correct answer should be around 20 seconds because light will need around 10 round trips to propagate in the direction where the wire is longer in order to reach 90 of the source voltage. I did a simulation on CST and found that in general the time taken is around 20c/L for wire with length L and width L/10.
This is on par with "why do airplanes *_actually_* fly?"
What about a non parallel line? Circular circuit for example.
if it takes 1/c seconds for the light to go on, what would happen if the wire were cut at the far end of the loop 0.5 s after switch is closed?
Is the wire length a reuse, are we talking about induction, and or capacitance? If this is the case, I suggest you re-examine your whole approach, because this video does not explain any of that.
How to make a Veritasium video:
1) Pick some unintuitive phenomenon
2) Choose a title claiming everyone is wrong about something, and you’re here to enlighten them.
3) Make a video explaining it poorly in a way most people won’t understand, and use a bad example to demonstrate it.
4) Go viral because people are baffled by your poor explanation and think there’s some black magic going on.
5) Wait for someone to challenge your claim.
6) Use challenge to generate even more controversy.
7) ???
8) Profit!
Soo… with the same hypothetical wire setup, if the bulb and the battery were at opposite FAR ENDS of the loop (1 lightsecond apart, rather than 1 meter apart) would the bulb take one second to turn on? Seems intuitively that the answer is yes?
Alright it’s been over a week, has anyone uploaded a real transmission line analysis of this to show what a realistic transient response would look like?
So the claim is for short times this is working as a big transformer and/or capacitor. Is that the idea?