The Big Misconception About Electricity
Vložit
- čas přidán 18. 11. 2021
- 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.
▀▀▀
References:
A great video about the Poynting vector by the Science Asylum: • Circuit Energy doesn't...
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
▀▀▀
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
![[Gegagedigedagedago] Help Old Chicken Nuggets Open The Gate And Get The Gift Box 👍️](http://i.ytimg.com/vi/neARexhV7y8/mqdefault.jpg)
I’m so glad this video exists. I use to completely not even understand how electricity worked, and now I still don’t.
lol
Same
I am still confused, but at a much higher level.
😂
Lmaoooo
Well well well, stepping into my territory, eh?! I shall make a video about this!!
Gauntlet thrown! I have my popcorn ready.
من فن شمام😂😂😂 فارسیم نوشتم چون میدونم ایرانی هستین
I would love to see your take on this
yo
I would love to see that!
Heres what i think, maybe it can help you form an opinion and make another great video:
I personally think that the light bulb would actually light up almost instantly, but not for the reasons described here. I think the cables are indeed what carries the energy, that transformers work by the magnetic field made by the primary side inducing current in the secondary, and that the reason the light bulb light up nearly instantly being that the charge in the wire builds up very quickly despite the wire being so long (this is assuming charge is conveyed instantly when there is no resistance, otherwise i would think that the bulb would light up after half a second). The wire gets charged, so there's a difference in charge at the light bulb. I believe that electrons do not have potential energy, the density of electrons in the wire is what carries charge, and charge is whats carrying the energy.
The telegraph cable actually disproves his take, in my opinion. If it was true, the signal would either never arrive, or it would arrive entirely normally. The reason it was so distorted is that the metal protection layer created a giant capacitor that caused all the distortions and slowness.
Also, if the energy was transmitted by electromagnetic waves, the inverse-square-law would apply, which it doesnt. If the electromagnetic waves stay equally strong throughout the circuit, that proves that the wires are what creates them, meaning they are what carries the energy.
(I shall update this comment whenever i think of new reasons)
I gave up learning. I burned out. But this channel has reignited my joy and love I forgot in my youth and curiosity I had for the World.
Thank you sincerely Sir.
That’s the point of these videos to feed you false information to stifle your imagination and make you stupid. Electricity flows through wires not around them, that’s why Guage thickness is needed for varying current strength.
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
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.
If the energy is transferred in the space extremely close to the conductor, and he said that electric field needs to extend through the circuit (at 6:15) , does it mean that he's wrong saying that the light bulb will turn on almost instantaneously (at 11:45)?
This should get more upvote, this is what I learned in college, also EE major here.
That's a really complete comment. It touches most of the points that bothered me. Thank you.
One frequent things I've been seeing on the comment section was the idea of cutting the wire midway through the experiment. From what I understand, I reckon the electric field will just propagate through the wire until it reaches the cut ends; at which point there will be no current and the magnetic field will drop off and no more power will reach the light bulb, correct?
+1 on the technically correct but very misleading train. Everything he said was true, but it implies something that's not quite right.
I'd love to see some calculations showing the current across the bulb vs time for the very long wire case shown in the video. If anyone knows a place where that's been done that'd be great!
It feels like a lot of the misunderstandings about this come from the classical simplifying assumptions that are made to make lumped element circuit modeling easier. Things like assuming that there's no wave propagation time. This means that the intuition gained from lumped element circuit modeling can fail us. This certainly gets me. The full time dependent maxwell description of this problem is much harder to reason about. The problem as posed seems like a good application of distributed element modeling
The other thing that surprised me was the professors talking about how there isn't energy in the electrons. Now this is also technically true as well, in as much as energy is mostly book keeping, but there's definitely an energy change associated with moving a charge in an electric field. You can turn the electrical potential energy into a kinetic energy of an electron. In an electron beam for example. And I feel like they both know and kinda say this, but the way Derek has presented this seems to imply something a bit different.
If misunderstood something then please let me know.
@@joshharrison2657 Veritasium in last few years summarised in one comment
I feel like a baby who just realized mom and dad don’t really disappear during peek-a-boo
😂😂😂
It's light, Joe, but not as you know it! (Or thought you knew it)
okay but they still can't see me behind the ankle-high curtains
Your dad might have been disappearing a little bit into your mom... so you weren't totally wrong
Hey, i'm very aware that you dislike people like me, but theres no other way to stand out really. I released a new song which you can find by searching "Thnked - Forever" or through my profile. I'd appreciate it tons if you could drop in some feedback as well. Thanks in advance 💗
so.. in summary - it's the making of the connection, from your appliance to the power plant, that then causes an energy field around the wire itself (near instantaneously) that causes the device to turn on. This actually makes far more sense, basically once connected the wire is 'live' .. there is no 'flow' back and forth, so to speak, the dissipation of energy around the wire and either end is the source of the electricity. (something like that). This also agrees with my understanding of EMI (electro magnetic interference) from electronics (disrupting things like wifi signals) from working in tech. Thanks for the video, well explained as always!
Interesting so what your saying is, the wire isn’t what’s charging the phone but the field. The wire acts as an anchor for the electric field so it’s centred in stead of just floating around as the incorporeal things fields are. Or did I understand what you said incorrectly
@@Montycarlo10 if I am correct, the magnetic fields "excite" the electrons contained inside the conductors, so electromagnets make even more sense.
If it's the energy field around the wire. What is preventing me from getting shocked when I touch the outside of the wire. I get that it's probably that I need to be part of the circuit that would create a field around me, but I still can't really wrap my head around it
Why can we not reuse electricity as it flows out one circuit and onto the next? I realize it is parallel, but still... Must there always be a return to the power station and not just simply grounded into earth?
@@IvanNavarroS I am thinking if you touch both the incoming wire and the outgoing wire, it is possible to get an electromagnetic shock. In the same way that you can light a tube fluorescent bulb.
Great video... I would add that for power lines it is important to understand that the wires are used as a waveguide to constrain where the EM flows. Unlike RF, which is high frequency, low density energy we allow that energy to flow through the air, without wave guides ( wireless )... I think it's important to understand the wires are 'waveguides' for power frequencies... similar to how roads and side rails are used to govern car traffic. Larry Durante, PhD, EE
Please explain how RF would work if we did not '"allow it to flow through the air."
@@enricofermi67 Hi Enrico, thanks for asking this question. The idea is that EM waves of different frequencies and resulting wavelengths propagate ( better word than flow, I should have used propagate) through mediums. So for whatever frequency and resulting wavelength of EM wave, say from ELF (3-30 Hz) and up through the EM spectrum ( let's stop at VHF (30-300 MHz) for this discussion and call that RF or FM bandwidth ) they propagate through a medium. The medium could be air, could be another die-electric ( so as not to cause too much energy loss ) and that medium actually affects the speed of the propagation of the EM waves. So my reason for using RF as an example was that EM waves travel (propagate) through a medium and they have a velocity less than the ideal speed of light in a vacuum. Undersea cables for communications send RF through die-electric centers with conductors on the outside ( outside acts as the waveguide and avoids the spreading of energy so it can go farther than when not guided ). The final point is the EM waves only go millimeters though a conductor ( because it's a conductor and the wave energy is eaten up before it can go too far ). But it does bounce off nicely ( like the side rails on the road :) and stays on the road). So can RF propagate in other than air? (yes). Can ELF propagate in other than air (yes). But air is very close to lossless and the wave travels nicely in it ( like the car on the road ). This supports your argument that the 60Hz EM waves travel in the air between the wires and bounces of the waveguides (the wires) . If this is not clear please let me know. Larry
@@larrydurante9849is the speed at which EM propagates through a medium dependent on the capacitance or inductance of the medium? I have been reading 100 year old books by Charles Proteus Stienmetz and have been trying to wrap my head around some of these concepts.
After watching this video I can confidently say I understand less about how electricity works than I did before.
Try opening your mind sometime ?
Yes, same for me. It is a new concept for me, so I am so glad about the video but unfortunatelly many questions raised that are not covered by the video...
Because it does touch on a more fundamental 'weirdness' (not really) about the universe that you didn't know about before.
@@alanwannemaker2518 But what if the information in this presentation is in error? How does that profit an individual to spend a lot of time and mental energy trying to understand something that may not be true. It may be like global warming, all garbage but we still won't quit talking about it.
Because he's lying. He's using misleading editing with the professors to try to make it sound like he's saying something counterintuitive. He's cheating the viewer.
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 CZcams 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.
When the first comment is the best comment.
You know the earth is flat.
@Tim Moles - 😂 that's the exact right thing to say when the scientific jargon resembles an extraterrestrial language.
So...why do we use wires? Couldn't we do without wires in theory, to transmit energy? Basically it needs nothing in between the switch and the bulb, why does he use the wire if it really worked like he explained in the video...?
No delay? Are you saying information travels faster than light, and that you've measured it?
I have a question @Veritasium, It may be a dumb one since I am pretty confused :)
In your case where the light and battery are positioned in the middle of `a` sides of the rectangle where the `b` sides represent the poles.
Does this mean that if you would put the battery and the light in the middle of the `b` sides would it take the light 2 seconds to turn on ? since the energy has to propagate 600tkm ?
Most intuitive explanation I've heard: Put down 3 coins next to each other, barely touching edge on edge, and firmly hold the 2nd (middle) one down with your finger. Smash the 1st one into the 2nd. The 3nd one will bounce away. This is how force is transferred without any noticeable movement. Same with electrons, but the electromagnetic fields are doing all the work.
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
Epiphanies can be painful, but we make them so. Your professor is clearly a devout scientist! Congrats to you both!!
That’s a great story and lesson! ❤
wanting to know the truth and rethinking you own knowledge, just to find out you've been wrong is a true sign of high intelligence.
👏👏👏
thinking that one is always right, on the other hand, is not
Reminds of when I was in 8th grade I argued with my elective science teacher about bullets firing in space his argument was based on the lack of oxygen and I knew that didnt matter since they can fire under water which doesn't have usable oxygen for combustion. I also liked guns growing up and its simple firearms knowledge that the use of self oxidizing smokeless propellants was a huge leap in their development. He reacted the opposite of your professor when we googled it and I was proven right.
"Power and Logic are not related." (-me)
People concerned with logic aren't concerned when they're wrong, but people use _use logic_ to wield power get upset when someone else is right - their power is tied up in being right.
(Note: that's the core to mansplaining too - explaining to assert dominance, not to bring equality of knowledge.)
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
This is a great story, thanks for sharing 🙌
Electric fields. Electric. Magnetic field can not light up a tube. Unless you create a loop which turns magnetic back to electricity.
@@marko_z_bogdanca how it works.dont know.but a tube will always light round high voltage
@@marko_z_bogdanca They are the same, it's just a question of the point of view, it's relative. 😉
Power lines can make fluorescant bulbs glow like that? I never knew. You could make a little epidode just about that. :)
Watched this and it blew my mind, in all my studies they talked a lot about the flow of electricity but not the flow of energy. This just made so much more sense then electrons rushing around a cable.
WOW, as a student major in physics, that is still amazing to me.
And here I thought all vectors were pointing.
With both direction and magnitude, oh yeah!
Wait till you hear about Killing vectors :-)
Pointing and poyntng are different👍
I C what you did there
(0,0) would like to have a word
WOW! I'm 80 years old. Started learning electronics in the Army in 1959. We were taught the "Right Hand Rule" in the study of inductors and transformers. Although we knew about the magnetic field around conductors we never applied that knowledge like this. Thank you for teaching an old man a new trick.
Nice
Wow u still study Great grandpa ji🙏
@@Abhinav-gu2ui Thank you. I love electricity in all forms. Except, of course, the CHAIR!
@@backlash00 do chairs really exist though
thats cap
Finally!! I've been looking for such a video for a long time. Clear and well presented, thank you!
Hey @veritasium love your videos been binging them lately. this is one of my favorites. do you think it is possible to conduct this field of energy without a wire?
I'm an electrician from the UK.
This theory can be proven by holding a florescent tube near a power line. It will glow. My family didn't believe me so I showed them. So glad you explained this in a way they understands fully. Thankyou. Very clever.
A total physics noob here, Im sorry if this is a really dumb question: But if a florescent tube can glow because it gets energy from the power line, why dont we get electrocuted just by standing near a power line?
@@shiraishichan3944 same doubt 🧐
@@shiraishichan3944 I feel its all about distance and what you are wearing. I'm sure if you got close enough with no clothing and a direct line to ground. You may experience ark jumping. Its a very good question 🤔
@@shiraishichan3944 hey EM waves not harm us ( like light not hurt you when it falls / passes through you) here energy is transferred by EM waves from the source to the electrical device which receive and convert to their known energy ( electrical)
When you keep a fluorescent bulb near it takes those energy which was carried by em waves
Same concept using in a current detector in a wire , we actually detect the em waves around wire which have more intensity near it
There is a difference between holding a power wire and stands near it
I know you predicted pushback, and with good reason, so here it is. I’m not saying this video is wrong, but at best, it’s incomplete.
First off, the fields can’t intrinsically be separated from the flow of charges as if the electron drift isn’t significant. For the magnetic fields to permeate free space in the first place, the charges must undergo acceleration to create them, and if you cut off the switch, the fields would collapse without the current. If I turned on a fan next to a piece of paper and the paper flew away, would it be accurate to say that the air alone did the deed? Sure, the energy that moved the paper was transferred to it by the air, but neglecting that the fan moved the air in the first place would be a glaring omission.
It’s also essential to remember that the Poynting vector itself is DERIVED from the continuity equation (local conservation of charge), and what it represents is the interplay between the energy transfer among the fields and the movement of the charges that generate them. In other words, fields don’t carry energy on their own without the movement of charge. Also, the vast majority of energy transfer in the fields happens extremely close to the wires, and the graphic that you’ve given of these fields taking such wild departures away from the circuit ignores the infinitesimal magnitude by which this happens.
With regards to your experiment, the following should be noted. Yes, there would be some current flow instantly with the closing of the switch, but only because the electric field in the conducting wire has had time to reach equilibrium along its length. If instead of a switch, you connected the wires to the leads of the battery directly, the propagation of the electric field along the circuit would occur at a speed less than that of light in free space. Lastly, I challenge you to explain the energy release from the actual light bulb that doesn’t involve electrons flowing through the filament.
Also, I posted the following as a reply further on in this thread, but I'm putting it here because it's important. The power (energy per time) that a circuit puts out is always IV (current times voltage). This relation makes no reference to fields of any sort. Now, it is absolutely true that the electric and magnetic fields carry the energy - the current does not - but when one takes the spatial integration over the Poynting vector, it always reproduces the power law P=IV. The fields carry the energy, but the current generates it. You can change those fields in a million different ways and the circuit will behave the same. For example, wrapping the wires in a grounded sheet of aluminum foil creates shielding, which is how high transmission data cables such as CAT6 or COAX reduce noise and capacitance between wires. You could say that they contain the electric fields within the space of the insulation. You could also coil the wires into an electromagnet. However you reconfigure the fields themselves, the fact is that the overall power dissipation of a circuit depends on the current, not on the field strength, and to trivialize this fact by focusing on how the energy is carried is confusing and misleading. As with my earlier analogy to a fan blowing air, the energy may be carried away by the air, but the amount of that energy depends solely on the power output of the fan.
Ultimately this video has some good information, but it is also extremely misleading, and I caution people to take any claims that “they way you understand things is false” with a grain of salt. Usually, there’s more nuance than that, and as something of a cynic myself, I think it’s often a form of clickbait. I encourage interested viewers to look elsewhere for the full picture of electrodynamics in all its beauty.
what would you recommend to read to understand it ?
I second Manuela's question. Apparently, you'd first need a general education in physics and only then would studying electromagnetism make proper sense. What would you recommend?
@@ManuelaNChannel @wii3willRule I'd argue without a fundamental knowledge if calculus and/or differential equations many textbooks on this subject would go over anyone's head. Assuming you have such a background, a text on microwave circuit theory (I prefer Microwave Engineering by Pozar) would help paint a slightly better picture of the EM processes occurring inside of a wire. A book like this would also speak on the applications of such methods in broader sense.
Ok, thank you. I had a sense that there was amore to the story, and that Derek's explanation was somewhat lopsided.
I agree, Derek purposefully took a topic lecturers debate about and gave us just enough fuel to start an internet bonfire and not enough knowledge to put it out.
He did this on purpose and we'll need to wait for the next video to find out why.
This isn't educational, but an experiment on who fact checks.
There's nothing wrong with poynting's therom, but also there's nothing wrong with traditional Electronics Engineering.
The only thing wrong is his transfromers and undersea cable explainations and then at the end pretending electrons don't have anything to do with it.
His entire electron flow was also missleading, sure it's slow and AC goes back and forth but think of Newton's cradle, one ball makes the ball at the end move without ever the traveling to the end.
Transformers excite different electrons on the other side, think of it as it's own generator if you will.
The undersea cable had issues with inductance that can be explained traditionally.
It's like looking at 2 sides of the one coin, neither side is incorrect they both represent the coin. However if you want to design a ciruit you'll use math that follows the electrons.
His video was misleading at best and the dislikes are worse than his usual. 176k likes and 4.3k dislikes and most people probably can't see them.
I feel like it's a social experiment or he's just desparate for views.
There's plenty of resources online for classical electron flow, not so many resources on poynting's therom, I would of expected far more and I couldn't find a single other resource pointing to electrons not doing the work. Derek has sources but not going to go out and buy those books without a better reason as to why.
love all your videos, because it challenges how we think about things and reminds me of basic assumptions on models we make, may not always apply. The only real problem (as an electrical engineer) that I have with this, is you show a DC battery and then show a light bulb being lit and continuing to be lit (caveat around that if we assume the bulb is so good as to be lit as soon as ANY current flows, in which case all the EMF and solar radiation from even the sun would be lighting it before you even turned on the switch..wink). You do bounce back and forth between DC and AC and the overall fundamentals of everything are awesome and great to explain to the layman, but even if you had a perfect bulb to detect the 1/Cs transmission and produce visible light response, it would quickly decay away and not actively light the bulb from the DC power transmission until a full second later. It seems a little misleading to show you flipping a switch, having the bulb turn on 1/Cs later, and STAY LIT on your finale... :P
Super interesting. Thx for making this video. Few serious questions do arrise tho. I have ideas on the answers but I want confirmation or just the answer. If electrons move through fields of energy, why even use the wires to conduct the energy ? Is it to guide the energy on an exact path from source to energy user?
Question numba two. Why do these fields of energy not shock or seriously effect us? Energy usually only conducts through us, when we touch the copper or steel in the wire. Is this cause theres a more dense or accumulated build up of energy in the wire comparered to the sosce around?
Hopefully sm answers these questions, cheerio 🥂
In my understanding of this, the energy is carried in the electric and magnetic fields and the magnetic field is caused by the flow of current and the electric field is caused by the potential on the wire. So your idea that the wire acts as a guide seems sound to me. Hope I have not lead you up the garden path.....
The fundamental law of physics: electricity disappear if you stop paying bills.
No its the laws of capitalism that govern the energy flow
Nikola Tesla said energy can be free , but are we willing to
hahaha
No
You can create electricity if you want
Many still it to
:)
Unless you own a solar panel
"Now that you understand how electrical energy flows..."
Bold assumption, sir! I'm still wrapping my head around this lol
Same for me, I dont get the difference between the fields always being around the wire, but also not being bound by the path of the wire. Like is that field a straight line from powerplant to your stuff or what? And why would that kind of energy only hurt if we touch the wire if its never on the wire but around?? Guess Im just really stupid
Yes I'm confused as well. Especially in the fact that from what Derek says, the electrons wiggle is just responsible for creating the fields that allow energy passage. So then... WHAT IS energy? What is actually driving my toaster and my japanese made napkin warmer? What kind of particle is doing the actual work in those devices?
@@wojtekmazur2416 That's his point; the actual energy is stored in the electric (charge density) and magnetic (charge in motion) fields, the electrons don't do any work the field does. Think if it like pumped hydro; the water isn't storing energy the energy is stored in the gravitational field, then when the water flows down the energy is being extracted from the gravitational field. Gravity is doing the work, not water. The same way the electromagnetic field is doing the work, not the electrons.
Hahaha totally 🤣
@@Kanglar this is such a good way of describing it
I love this video. It answers many questions about magnetism. My comment is: When you cut across a conductor that has a black and white conductor and is conducting both fields, and create a short circuit, the power is interrupted within both pathways with a dramatic display of energy. My conclusion is: The two fields are not seperate entities but are one emmanation. It would be awesome to see another video that explains the short circuit and the interruption.
Well this video answered some questions of mine, but raised many more. One of being that if the battery and bulb were kept far then the field should take much more time? right? So if it were kept 1 lightsecond far then will the time between it lighting and key closing will be 1 sec?
No, he was wrong about it "jumping" straight over to the light from the switch. The fields surrounding both are separate because the field runs along the cables itself. It would travel up and down the cable near the speed of light, BUT in the field, not in the wire.
Honestly, the analysis from the professors made a lot more sense to me than the video just from a small clarification that I didn't catch from this with one watch, and had left me very confused. The energy most are generally used to seeing from a long, wired connection is from the "transmission line" current, but the energy being talked about here is from "antenna current," and the two modes of transfer, along with major differences in voltage that actually reaches the bulb by either type, felt like important info to leave out. The implication I got from the original video was that the length of the conductor did not matter at all for this model, but the reality was just that the 1m distance in the math, and specification of "any" current, hid the conflicting nature of two modes.
So, from my corrected understanding: The "transmission line" current *would* take one second to reach the bulb, through electron to electron EM field interactions in the wire, it's just that the "antenna" current can travel there first, because of a lack of shielding, and the misconception/lie here isn't so much a misconception/lie, but a lack of information on additional modes of energy transfer.
It felt like this video was more focused on becoming a popular, trick question via omitting information, rather than informing people on new or misleading information, which is not something I would/could say about any other Veritasium videos I can recall, and I do not like to say.
Sounds like the one on autonomous vehicles. Thank you for clarifying what was missing here
Agreed entirely. This felt more like a parlor trick gotcha rather than any deep (causality-violating) explanation of a fundamental misunderstanding around electricity
Reviewing the comments, I see that many others share the misinterpretation that I had, and I feel that is not a good reflection on the clarity of this video, with many accepting that interpretation as fact even in the case of others pointing out causality issues. If I am wrong, I will accept that, but this is my current opinion upon what I have seen as of now.
well I mean the question asked was how long till the bulb lit up. It doesn't matter about how long the current takes or anything else. just the bulb. I think you just didnt listen to the first words of the video.
I guess the next question would be what's the ratio of antenna to transmission line current in standard environments, how significant are the two sources.
The central issue here is the muddy definition of the bulb being "on". It obscures the fact that there are two separate events in terms of current in this scenario.
1) After 3.3 nanoseconds, the light bulb will experience a very tiny electrical signal. This is true even if you cut the wires, and has more to do with antennae than circuits. (Hell, you might as well say the light bulb will turn on *before* you close the circuit due to the ambient radio signals)
2) After 1 second, the light bulb will experience the full voltage of the battery like it would in a "normal" circuit.
The energy does travel along the outside of the wire, but the vast majority of it stays very close to the surface of the wire. Thus, when talking about energy propagating in circuits in any real sense, it does need to travel the entire length of the wire.
Very simple and clear explanation! While the whole video confused me, this simple 3 paragraph explanations made it very clear.
Thanks
So if the only switch is at the wire extremity (half a light second away) and is open, then the capacitors are charged and in steady state => light is off
When I close the switch (half a light second away) then the light will take half a second to turn « on » right?
Yep! The visuals in the video even show this. While a small signal magnitude will cross directly, most of the flux vectors do actually have a length close to that of the wire. Hence why none of the Profs at the end wanted to guess what would happen in a real experiment because none could guess the "on" conditions
@@christiansimon399 you're going to get a signal quicker than that. Think what the OP said about antenna. It's a direct path. In terms of the "full" voltage, then yes, it will take longer
@@christiansimon399 Interesting question. I don't know exactly how the wires would behave in terms of the antenna effect in this example, but we can neatly step around that detail!
In your example, the switch is half a light second from the bulb. So due to relativity, any effect of you closing the switch *must* take (at least) half a second to reach the bulb. So to the extent there is still an antenna effect, it will take half a second to reach the bulb. Which is about the same time it will take the full voltage to reach the bulb.
After having done my masters in Electronics and Communication, from NIT Rourkela,India. Why did I start thinking exactly what is explained in this video.....!! I am glad that this video exists and recommended to me by CZcams. Thank you..!!
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!
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?
Hold up this is a really good question I'd like to know what happens too
This is an interesting question
You perceiving something a second later does not mean it did not happen a second ago. So if at the time of turning it on it gets cut, its not gonna light up.
How would that work for the cutter? He wohld cut it, and then he would perceive that the light would be switched on a second later, so he would perceive it as being turned on a second AFTER his cut.
Both are wrong as its not about the observer. Its about the event itself.
This question should go up
if we cut the wire then the tow wire connected to the battery act as tx antenna and the other act as rx antenna so the bulb will emit only a flash .
Derek is somewhat right about the time being roughly 1m/c for the bulb to light up but only because the parameters of the problem were picked to be tricky (sometimes fun and educative). Unfortunately Derek doesn't go into details in the video and only says that the bulb "won't receive the entire voltage of the battery immediately". This may mislead you into thinking that the signal speed in an electric circuit depends not on the length of wires but on the air distance to the switch, which is wrong. The signal speed in wires is roughly 50-95% of the speed of light and most often is what dictates how long it takes for something to turn on in most circuits. This is why, for example, matching copper trace lengths in PCBs is often important. Or why high frequency trading companies care about their internet cable lengths. HOWEVER, often in circuits there's significant wireless EM radiation, intentional (radio, wifi, microwave) or unintentional (reduced with EM shielding). Turns out that in Derek's circuit one side of the wire initially acts roughly like an antenna while the other acts like a receiver and the power transmitted could be enough to light up an LED bulb. At 100m it wouldn't.
This is the exact reasoning I was looking for. Thank you!
Your answer (1m/c seconds) is correct. The video answer D: (1/c seconds) is nonsense, because 1/c has the units of seconds/meter, not seconds.
thank you
Are you talking about inrush?
I share this sentiment. The EM influence at 1 meter takes 1/c seconds. But unless one has a clever inductive power transfer, not likely to light up the bulb. I tried to do the experiment today in the lab with 30 m of wire to make a video but the problem in the real world is dealing with inductance of long wires---but that said, I could kinda measure a 200 ns delay so at 100 ft, 50% the speed of c, that delay is right on par with what one would expect if the power has to traverse the length of the wire. A wire has the ability to contain the EM fields along the wire path and thus transfer power efficiently. However, with all this talk of wireless charging and some MIT breakthroughs, I can see this as a segue to that topic.
Very good visuals in explaining wave energy (Electrical and Magnetic).
Mind blowing !! Thank you ! I am so inspired by you that I subscribed to Brilliant !
I am a third year Physics uni student and I can onfindently say that you have managed to explain the poynting vector better than any of my professors ever have...
I bet
That’s because I bet none of them have ever taken any education classes (not required if you can believe that).
Isn't that the truth. And also after working in the field for many years. I learned so much more on the job. Hardly anything I learned in school whatsoever.. barely. Just the basics.
Bro you need to watch some Eric Dollard lectures... I would recommend "History and Theory of Electricity" and "Origins of Energy Synthesis" right here on CZcams if you really want to get at understanding the essence of electrical phenomena.
Just remember that a Theory of Everything has grave implications for Aerospace and Weapons development, and thus has major national security implications should it ever be out there for all the world to see, and thus why for the most part, we are kept in the dark as a member of the general public on topics that get deep into the essence of the reality of nature and natural philosophy!
@@Defooriginal he misspelled confidently....so you're just as wrong? 😆
man, I'm generally a fan of yours, but I do hope for an errata on this one.
You're absolutely right regarding the fact that the energy is propagated by the fields, and not the wire. But your explanation (and specially the answer to the '1c*s wire question') hides the importance of the wire: IT GUIDES THE WAVES. Without a wire to guide the waves, you can't propagate the energy at all. Meaning: the state of the wire is important. If the wire gets cut, the energy won't be propagated, as common experience shows.
So with the long wire situation, the fields will take time to propagate based on the length of the wire. Not because the energy is propagated by the electrons, but the wire is what guides the waves from the source (battery) to the load (lamp). Think about it: if the energy arrived 1/c seconds later, what's the point of the wire?
Of course there are secondary effects (through capacitance, inductance and radiative effects), but these mostly die out at a time scale much shorter than 1 second, and are much, MUCH, less capable of transmitting energy than the conductance effect which is capable with the wire. You mentioned this briefly, but your brief explanation (and the graphs you show) implied that you were talking about transients (since you said it depended on the impedance), but transients also only travel at the speed of light.
A cut wouldn't let the wire form fields at all
> Without a wire to guide the waves, you can't propagate the energy at all.
Not true, this is exactly how antennas work!
Did u not read the top comment?
@@adelelopez1246 yes, now compare the efficiency between a guided system and a radiative system. You barely feel the fields when they are radiated.
There are wireless energy solutions though. You can transmit electricity wirelessly.
So question if the line is cut in one point how long does it take for the light to turn off, I don’t see how it could be faster than the speed of light as a that is the fastest information can travel. And a follow up to that is if the switch it turned off and the path is broken at the same second the light should still turn on immediately right because the information that the path is closed was not received. But the path is broken so how is there any current flow?
This was so cool. I didn't get the answer until the battery / light demonstration about halfway through the video.
This video: "Forget everything you know about electricity."
Me: "Way ahead of you, as I already know nothing."
Hahaha exactly what I was thinking
Me too. :D
I know that I am intelligent because I know nothing.
- Socrates.
None of the above
As said in the video most if not all doesn't know the real thing even the experts in the field.
As a tradesperson who has created and installed many home wiring circuits, wired up car stereos, installed lights and even built circuit boards; you have shattered the sense of pride and accomplishment in what I've done by pointing out I didn't REALLY know what I was doing. I'm going out to rub two sticks together in order to claw back some small semblence of human ingenuity.
You and i sir, i feel that everything in my life is fake and i have been lied to all my life
To be fair, this is very misrepresented in this video and arguably incorrect even though everything stated is actually true.
Ultimately the power is inducted into the light as the em field generated around the battery and outgoing wires propogates outwards at C. IE: its basically the same type of inductance you see in an air gapped transformer where current and voltage are generated in the light by the inductance of the power from the battery after 1/c seconds. So yeah technically it is "on" (sort of at an extremely minimal state though it would not be visibly on). With what we classically think of as "turning on" occuring at 1sec once the electric current also travelling at c (along the longer path) reached the light through the conductor.
Don't feel to badly. All this desktop research about power transmission is really interesting but how many of "them" have wired the same number of houses successfully as you have?. Still I am grateful for the knowledge shared here.
I got the same rude awakening but once I accepted it I feel much more excited about the possibility of free energy from tapping the earths natural magnetic force and static electricity. I believe Tesla’s experiments in this field we’re grossly underestimated ...or purposely sabotaged.
All we need to learn now is how to throw the “on” switch to power our homes, cars, airplanes etc.
We already know we can run cars trucks and airplanes on electric motors. All we need is to find the vector of the flow to find where to put the “on” switch.
@@Peter-gq8uh I agree. I’ve watched electricians wiring new homes and how fast they move through the room. The wire literally seems to become molten and flow into the switches and through the metal boxes into they’re receptacles. They become so fast you hardly see the insulation flying off the ends of the wire and they’re already connected to they’re receptacles.
Understanding the mechanics and engineering of something perfectly and making it work does not involve the science of electro-magnetic flow and chemistry, physics and other scientific facts. And thank goodness for that or we’d still be living in potato huts.
OMG! BEST EXPLANATION EVER! I was an A+ student in only one class in my life, electronics! I always found manipulating and controlling electricity in various ways, exciting, appealing, easy and yet still kind of mysterious. I accepted the explanation that "electricity" was defined as "movement of electrons from the outer shell of one atom to another" but it never made sense to me how they were consumed, or how alternating current actually worked. All that nonsense they teach about alternating current, I always said was "explained what was going on" but not the "why, and how". I truly thought no one alive actually understood electricity or at the very least, alternating current... Man was I wrong, and I'm so thankful for the education!
Read C.P Stienmetz's book (the guy who reverse engineered Teslas AC motor.) Its called Theory and Calculations of Alternating Current Phenomena. It's a free PDF online. And trust me it will clear up what EM is and electricity. Completely different from what we are told. He was an absolute intellectual powerhouse. He was the Stephen Hawking of the 20th century. A small dwarf with a twisted body. So all he had was his mind. But this video is the tip of the iceberg and tbh not really correct in some ways. But CP. Stienmetz says without a doubt that energy flows in the fields around the wires. And that the charge flow/electron drift is a side effect of this not the cause of it. Like the shadow of a moving train. Hope you get it. All his books are amazing when it comes to understanding Electricity.
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?
Still having one doubt: I understand that energy doesn't need to travel through the whole circuit, but how does the light bulb know it's a closed circuit when you flip the switch? Let's say the wire is cut off somewhere very far away from the switch and the light bulb, information should still take time to travel instead of instantaneous. Unless it will work even if it's not a closed circuit, but this doesn't make sense either. It's like I can just flip a switch near a light bulb and it will magically work without a closed circuit. I know it may work without a closed circuit like a transformer, but this setup is not like that at all.
Also, mentioned by Rick K in the comments: If this is true, then why don't we use that effect for "faster than light" data transfer? If the light bulb "reacts" to the switch almost instantly, that would mean that the "information" transferred with the flip of the switch is also transmitted instantly.
I asked basically the same question, hope somebody explains this
Very interesting take, can't wait for the expert responses.
I have the same concerns, definitely an interesting topic
The information still dont travel faster than light. it just takes a more direct way. We basically already transmit information this way with radio waves. I am still corious about the explanaition of the first part of your question tough...i dont grasp that either
dude do you realise, the speed of light is like, mind numbingly fast? it might not be instantaneous but it's the closest you can get to instantaneous!
The part about AC was mindblowing. The Poynting vector is S = E x B but if both E and B are reversed, then S = (-E) x (-B) so the energy flow stays the same!
For me, that was one of the only parts where I was like "oh, yeah, I know this one!" ahahah! Everything else was mind-blowing!
The visualation was the only why I would have understood that concept. Seeing the diagram, I immediately recognized it as just rotating the circuit along the axis. People who can look at numbers and gleen the same information are wizards as far as I'm concerned.
I absolutely read SEX the first time I saw your comment. Had to do a double take, lol.
wat
@@FranciscoPower same lmao, I'm still shocked for everything else, I guess I have to watch the video a few more time
Oh good grief and yikes! My heart fell into my socks when you said the chain analogy was wrong. When I saw you do it, my little light turned on. When you said it was wrong, well, I am completely in the dark. You have broken me 😉! The rest of the video flew WAY over my head, and I can't imagine ever really getting it. Only today did I finally understand that conventional vs electron flow doesn't matter, and I made the switch to conventional and things made much more sense when looking at circuits and schematics. Now you have taken that from me too.
I am joking in a way, but as a whole, this is very upsetting to me. Is there something I can look at in regards to this, or should I just try to forget that I ever even saw this and go on my merry way? I'm serious man. I need help.
Perhaps some of you remember the sitcom called The Jeffersons. In one episode George exclaimed, " It's electricity! Nobody knows how the hell it works! I used to think that was funny.
Also, if all of this is true, how do elections move through earth ground back to the grid?
I am deep in a rabbit hole!
Excellent explanation. Thank you, Sir.
If you believe that crap you believe in the tooth fairy
Like a lot of comments on here, there is a big problem I saw:
You’re severely undermining the importance of the cable. Yes, the magnetic field carried the energy for the bulb to light up. But the field is strongest right at the wiring. The instantaneous power going to the bulb is a very small fraction of the field. The wire acts not only as the way for electrons to flow, but also for low impedance transmission. The transmission through air is much, much smaller than transmission following the wire.
EDIT: Veritasium's new video clears up the major hole that this video brought up. His visual representation of the circuit in the original video was the major issue. The point I made still stands with that representation (insulated cables, car battery, lightbulb). I'm glad he refined this.
That is exactly what I thought after watching the video. The power transmitted through the EM field has the highest flux inside the wire due to metal's high permeability. If the power could as easily travel through air as through metal, we wouldn't use wires to transmit energy/signal in the first place.This is correct that the light bulb in the experiment would light up after 1/c s, but it would be initially very dim, and gradually increasing in brightness until after 1s, when the EM fields traveling through the wires catch up.
Didn't tesla come up with a death ray because he thought that we could transmit energy through the air effectively?
@@mateusz7590 Uhm...he did say exactly the same thing in the video, tho. I think people are just pointing out at simplifications made for divulgative purposes.
These "thought experiments" are never meant to be broken down, otherwise you will always find mistakes. They are obviously wrong, that's the whole point, otherwise we can continue adding an arbitrary number of real considerations and debate whether my personal choice of considerations are more accurate than yours. In reality none are, they are just meant to more easily represent a specific phenomenon, such as the fact that energy can in fact travel through air, which was the point of this video.
@@mateusz7590
Yes, there will not be enough energy transferred to the bulb until the waves have traveled sufficient distance down the wires to induce enough current at the bulb--even over one meter there is going to be quite a drop in power. He seems to imply that the energy jumps from the battery to the bulb with sufficient power to light the bulb--answer was D.
At the end of a very intese physics course and right after the exams, our teacher ended it by telling us that everything we had just learned about the flow of energy in an electric system was most likely wrong and mentioned something about energy not passing through the cables.
Now I finally know what he meant. Thank you 😅🙇
What are the cables for then?
@@rocketpig1914 I might be wrong, but I think they are essentially allowing the magnetic field to form properly in the loop configuration and essentially becomes the structure the fields will form around. So for example, without the cable, you can't turn on a battery or switch and just power your devices, it needs a bridge to stabilize around and focus it's energy into. But maybe I am flat wrong, but this is how I am kinda understanding it
@@rocketpig1914 I believe they are to transmit those fields to your home, otherwise they'd disperse.
I'm actually dumbfolded by what I just learned.
I do remember thinking it was weird that a ring voltometer could work at all, If the coating of wires was a good enough insulator to protect me, why would a voltometer work at all? I won't pretend I've fully grasped the info in this video, but it does help me realize the importance of the field itself.
A teacher saying everything they just taught you was wrong is such a baller move, honestly. That's how you keep people curious.
The energy is transmitted through the electric and magnetic fields around the wire. Why does a wire get hot if you "pass too much current through it" if the energy is being transmitted outside of the wire? Does the wire's resistance cause it to act as a roadblock to the fields around the wire and they end up imparting energy into the wire itself?
The wires resistance is directly related to its effectiveness as a field reflector, the higher the resistance the less efficiently it can reflect the fields and the more current will "seep" into the intermolecular structure, dragging on the wires atoms and causing heat.
Unlike the Dielectric/Electrostatic field the Magnetic field is spatial in nature, the more you try to shove onto a wire the more pressure builds up like trying to overfill a water bottle, eventually the pressure becomes too much.
Almost everything that uses electricity in your house uses electricity that is converted from AC to DC. Light bulbs, door bells, toasters, ovens and stoves, fans and maybe a couple other simple things can use AC current, but not you TV, Stereo and anything else that functions at a more complex level uses DC.
I really like how you post a poll first and then post the video with in-depth explanation later, keep at it. :D
Oh where did he organize polls
Great way to get a ton of engagement and boost the video in the algorithm, too.
@HARSH MAURYA It comes up when you’re on CZcams app and subscribed and all notifications allowed.
@@harshmaurya7639 community poll of CZcams
@@harshmaurya7639 you can check his community tab in his channel
Considering how long ago we learned to harness electricity and create electrical circuits and how much misconception surrounds it, makes me wonder about other things we've misunderstood yet utilized nonetheless.
Yeah its very interesting to think about. I wonder if there’s any math we use in common practice that’s not completely accurate and would therefor disprove scientific theories we’ve accepted as being true.
It is fascinating how often heuristics can be just as good, or sometimes even better, than actual absolute knowledge. "Rationality for Mortals" and "Antifragile" are two books that talk about that idea, more so the former, the later kind of hits it tangentially.
@@johnwiand1167 yea i know how ya feel, but we already know that all established math formula give no certain answers without some margin of error, even 1 + 1 = 2, whatever that 1 of something is that your adding is likely not going to have to same number of atoms as the other 1 of something your measuring therefore your answer must be a decimal value.
further, even electrons, protons, and neutrons have mass that can be calculated to some approximation but impossible to measure exactly which makes measuring anything exactly impossible.
Yes - a lecturer once told my class that we (humans) understand radio enough to make it work for us but 'exactly' how it works is still a mystery - to be fair that was 30 years ago!!!
Women?
Still nice to know that ohms law and its ac derivatives "work" though, how resitivity and cross-sectional area of conductors play a part in the ability to transmit/pass current (the flow of electrons) which is requred to perform work. There's also the confusion of comparing sending/modulating energy for communications purposes distorting dots and dashes (interrupted dc back then) vs sending energy for "work" purposes. The concept of free electrons drifting between atoms under the influence of EMF is a pretty good fundamental model to have, Newton's cradle is often used as a visual prop/way of thinking about it.. Transformers (and capacitors, even optocouplers, acoustic couplers etc) are "breaks" in the circuit for the electrons, but not the energy, as it's transformed from one type to another and back again.
Thanks for such interesting video.
After watching the video, I do have a question.
What if the light bulb is inside a metal box (all 6 faces are metallic and there is no gap in between, just perfectly metal, and of course the light bulb is still connecting to the wire to form a complete circuit ), will be light bulb can be switched on in this situation?
What I understand is that EM wave will be blocked by metal, even if a thin metal foil can block its traveling, and so does the energy of the EM wave.
I believe the Iight bulb can be switched on even if it is inside a metal box, so if I am correct, then how can we explain the phenomenon if the energy is coming from space outside the wire.
I am just curious. Thank you.
The perpendicular component of the flow of energy will appear between the wires inside the box, even if the box somehow completely blocked the exterior fields the wires that are inside it will still partake in the same activity.
As far as I understand anyway.
He is simply talking about induction. Like in a Transformer. You don't need a metal box, you just need to move the bulb outside of the area where the field will be around the switch when the switch closes. Then the light will only turn on when the EMF travels the full length of the cable.
This actually raises more questions than it answers.
yeah i think that was the intent of the video... classic youtuber ploy
Yeah. But it is so with all knowledge.
means there's more to learn
as always;)
it SOO DOES!
naah everything is solved.
I am a lowly aircraft electrical technician and mechanic. But from troubleshooting aircraft systems over the years, a fuzzy picture started to form in my head almost exactly like what you illustrated. And I've used that image to do mental checks in my head against where power is going, and if my diagnostics are correct or I have my test equipment in the wrong place. This video completed the puzzle in my head, and I think a lot of people in the blue collar world who work with electrical systems every day without ever defining the knowledge they've learned from it will appreciate seeing this video.
Yes, most people in practice think about electrics as about hydraulics. Closed system where medium (electrons) runs around and does useful work. Pump = battery, power supply, hose diameter = voltage, pressure = amperage, current, viscosity = resistance, valve = switch, check valve = diode, hydraulic motor = motor, accumulator = capacitor, etc. This way of thinking will allow you to solve vast majority of electrical problems.
But the reality is much much more complicated.
I think he's playing games with us rather than teaching for clicks. Electrons move and they generate EMF, they're 2 sides of the same coin and can be looked at from eitherside.
Nothing wrong with what he said except it doesn't invalidate the otherside, that part he said about it being purely academic, he knows what he's doing.
That's why he's getting more dislikes than usual.
Dear SyTy, I sincerely suggest that in your work you follow the procedures established by the aircraft manufacturer and NOT your feelings and impressions you're getting from youtube videos, even ones of such respected authors like Veritassium. As a pilot, I sincerely hope you do.
@@cheburatorish he's loosing respect from me with every viral video he does. He's a youtuber first now, teaching isn't his primary agenda anymore.
@@Commander_ZiN Wait, you're still seeing dislikes? I thought CZcams got rid of them. I certainly can't see them anymore. I suppose they may be 'phasing' it out? Not sure what the point of that would be, though.
This is an elaborate explanation of what's going on, but nobody fully understands why and how.
I suppose there is background knowledge at an informational level beyond the reach of the human rational mind. But the main thing is: it works!
This is such a good channel. Im obsessed 😍
My grandmother lived on a very remote and isolated island in Norway. When they first got electricity, they had one lightbulb connection hanging from the ceiling in the best living-room (it was only used when having fine visitors). The thing was that when the electrician first lay out the cables, they had no bulb to put in the socket. Also the electricity was not yet connected to the house but would be soon. So each night they put a bucket under the empty socket just in case the electricity would be connected while they was sleeping. Not to spill anything on the floor.
Nice story
Lol that's amazing.
Wow
A colleague's grandparents, living on farm land in Belgium, would dress up on Sunday to watch television, thinking the presentator was actually talking to them and did see them.
I have a friend who turns off the switches on all his unused power points - not because of safety, even though that's sensible - but because he believes electricity pours out when there's nothing plugged in, wasting his money.
I have so many questions:
- If the energy moves through the fields, how does it light a bulb? What takes on the energy?
- People in the comments talk about shielding the bulb from EM fields. How does it work then? I need pictures.
- how do computers work, transistors, if it's not the current that moves the energy?
Give us more of this!
For the first question, the energy, after traveling through the electrical and magnetic fields from the circuit, will reach the bulb which has its own magnetic field around it. The energy will travel through that field and pass through the filament, thus lighting the bulb
The point being made is that the long wires back and forth will function like an antenna, and so the switching on will create a wave that is propagated over the distance between the antennas. The bulb will sense this (arguably quite weak) wave and flicker on. As an engineer I find this experiment a little frivolous, I think it will confuse people more than it educates people
@@jemert96 Exactly. You can see it as a two transmission lines or antenna. And it's unrealisitic long wires. I find the presentation kinda dishonest either way.
@@jemert96 Great point, thank you.
@@jemert96 It is also worth mentioning, that let's say two 300km straight wires with 1 m gap that aren't actually connected will for 1 ms (thinking about it, likely 2ms, but not so sure about that) act exactly the same as the 1c long cable. And the "not whole current" after the 1/c will be so minuscule, that nothing will actually happen.
The fact that people disagreed with this when we've all known how the Capacitance of Capacitors can be increased by bringing their electrodes closer together is wild to me.
It should also say something about the principle of that, the capacitance rises as *space decreases,* it should be obvious something is going on there that is operating on inverse principles.
And if you follow the work of the pioneers of electricity, including Thomson, we discount the particle model of the Electron and by extension remove charge separation as even being a thing, so something else is going on.
Amazing channel. Congrats. What if the wire extends to pluto?? We would have the same results??
As a graduate student in EE, I have to agree with the skepticism in the comments as this video is very misleading. (Note: see edit at bottom for additional clarity)
It is accurate up until the conclusion, which means we can use information presented in the video to contradict the claim at the end. I present this to showcase why the argument is logically flawed, and is by no means a proof.
a) 6:00 and 6:58 - Presents the concept of electric potential, inducing this type of electrostatic field. The direction of flow of positive charges is visually shown
b) 6:06 and 7:04 - Presents the concept that a magnetic field is induced if and only if electric charges are in motion - "Since no charges are moving, there is no magnetic field"
c) 6:13 - Presents the concept that when both ends of the battery are connected to the system, the electric field (and thus the electric potential between the conductors, assuming they have no impedance) propagates at the speed of light through this medium
d) 4:37 - The expression which describes energy flux (Poynting vector) is proportional to E x B
Lets take the thought experiment presented at the beginning of the video, and lets say the switch closes at time t = 0.
1. t = 0- (an infinitesimal point in time BEFORE t = 0)
Using a): there is no electric potential across the bulb, because the switch has not closed.
Using b): there is no magnetic field anywhere, since there is no current, because the switch has not closed.
Using d): S (everywhere) is 0, since there is no electric or magnetic field
2. t = 0 (right when the switch closes)
Using a) & c): there is no electric potential across the bulb; the field has to propagate at c m/s through the medium of the wire.
Using b) & c): there is no magnetic field across the bulb, since there is no current at the bulb. In addition, there is no magnetic field anywhere since there is no current yet.
Using d): S (everywhere) is 0, since there is no electric or magnetic field
3. t = 0+ (an infinitesimal point in time AFTER t = 0)
Using a) & c): there is no electric potential across the bulb; the field has to propagate at c m/s through the medium of the wire. t = 0+ is still an instantaneous case
Using b) & c): there is no magnetic field across the bulb, since there is no current at the bulb. However, there IS an induced magnetic field caused by current starting to flow at the switch. The electric field is starting to propagate at c m/s, and there is a slight electric potential at the switch the moment it is closed, causing the flow of current
Using d) S at the bulb is 0, because there is no electric or magnetic field there. S at the switch is non-zero, since there IS an electric or magnetic field.
Therefore, using c), it can be determined that as the electric field propagates toward the bulb, so does the magnetic field with it. ONLY when this magnetic field reaches the bulb does S become non-zero AT THE BULB. S also propagates alongside the wire at c m/s.
It would be silly to say it just "jumps" across. Yes, there is a positive flux of energy the moment the switch is closed, but it is not at the bulb nor is it going to power the bulb. It still takes time for this energy to propagate, since it is directly dependent on the E and M fields. Which, if I haven't emphasized enough, propagate at c m/s through the wire
EDIT:
I want to clarify that this is merely a criticism of the way the video presents the topic, not the topic itself.
I did not discuss transmission line effects that can occur when the wires are placed so close to one another, though this is the single acting phenomena which can cause near-field disturbances to surrounding conductors. It is truthful that the opposing wire can be inductively energized under specific conditions (still not enough to power the bulb at maximum brightness, assuming maximum brightness is when the bulb bears the entire voltage difference of the source), but the video ignores to explain phenomena to its full extent and exaggerates its conclusions.
The best analogy I can give is imagine a video on kinematics. Concepts are introduced, given the assumption that there is no air resistance. And then there is a claim at the end that can only physically be possible under specific conditions of air resistance, but there is NO mention of air resistance the entire video. It tries to attribute some phenomena to a seemingly unrelated (but precursor) concept.
If this video were to discuss transmission line effects and not confuse them with actual power transmission, then I think it would have been a great and informative video.
I didn't expect to see such nonsense from the Veritasium channel
d/c where d being the length of the wire is the answer to his question.
I agree that this video is misleading, and the premise Derek presents breaks down the moment you look at data signals (which are just electrical packets). On a dense electric circuit or motherboard, the length of traces directly affects the "skew" of data signals being transmitted through it. If the response at the other end happens at x/c s due to change in magnetic flux, then all data signals would essentially arrive at close to the same time, but this doesn't only not happen, but would be impossible in practice because of the resulting crosstalk.
I also disagree with the video's conclusions.
In the demonstration, the power source is a battery. That is Direct Current.
There will be a very small and very transient period of time where the EM Wave will have a brief pulse, followed by a very long and gradual pure DC voltage.
The EM wave from the moving charges in the conductor will emanate from their source (very slowly moving electrons) and this EM Wave will be strongest near the source of the charge, and radiate outward. As the EM wave radiates outward, it will get weaker and weaker. By the time it reaches the "Bulb" after traveling across 1 meter of air gap, it will be far to weak to "light a bulb". The light will turn on after the EM Wave travels along the conductor and reaches the bulb in approximately 1 second.
This video has confused transmission theory with power transmission thru a conductor.
The energy transfer from a DIRECT CURRENT source will not behave like an AC source.
This is NOT a Tesla Coil with thousands of volts. The video clearly shows a battery. Not a lightning bolt. A battery. There will be very little if any induced voltage or current on the bulb, certainly not enough to keep it on.
Looking at it another way, as the Poynting Vector is the cross product of the electric and magnetic fields, aren't these field largely concentrated along the wire given the high permittivity of the conductor (which confines the electric field to the wire and consequently the magnetic field with it). Therefore, while there is some coupling of the Poynting Vector directly from the battery to the light bulb (per the graphics in the video) this is limited by the very low permittivity and permeability of free space? (And yes, I know I'm simplifying this by assuming this is in a vacuum but that should be acceptable for the purposes of this thought experiment as we've already made a simplifying assumption of no impedance in the conductor).
So, given the the majority of the energy transfer is via the conductor itself, there should be a propagation delay that is resultant from the limits imposed by the speed of light.
Another interesting twist on this is what would happen if the light bulb was not simply 1 m across from the battery but at the end of the 1/2 light second conductor?
Yet another twist, what if one conductor to the bulb is 1/4 light second long and the other conductor is 3/4 light seconds long (the total length of the conductor being the same as the first two scenarios)?
I need to go get my Applied Electromagnetics textbook out.
"What you were taught about electricity is wrong"
Me (an electrical engineer): "I sure hope not"
Same, except as an electronic engineer lol
Lol same
What he ment to say is that what 99% of the population was taught about electricity is wrong.
I found myself saying; "that is very interesting. My knowledge of power plants and electrical fields generated within power plants leads me to believe that this is more likely true and I wouldn't disagree with the conclusion."
Damm that degree
Everyone's stuck on information traveling faster than the speed of light, but it doesn't..
It's traveling 1 meter in 1/c seconds. It just doesn't take the path we've always been taught in primary school..
This is giving me flashbacks to a physics course in uni that helped me decide to drop engineering for compsci.
I'm a little bit confused. Would 1/c not mean that it propagates faster than light in a vacuum? This should be impossible, right? As far as I know electric fields can only propagate with c. And as far as I know the problem is exactly that with very high frequencys in electronics. If the conductors are too long there is not enough time for the propagating field to the trasnsistors before it is altered at the source. Or do I have something misunderstood?
Edit: The explanation from dylandailey3191 does it for me. This, for me, was not clear enough presented in the video.
Hello Derek, a physics professor here. I love your videos and I subscribe to your channel - in all honestly, I consider it the best example of public communication of physics and science I have ever met - I am not exaggerating. I actually used some of your videos when teaching to my students. However, you did not convince me with this one - not that I love you any less for this. I have similar objections to some that have been made by others here. The explanations of the fields, and the Poynting vector are gorgeous and very instructive, by the way. But I have tried to explicitly calculate the flux of the Poynting vector on the bulb, and I find it to be quantitatively a small effect (quickly dropping with distance of the bulb). Yes, there is *some* disturbance at the bulb, but I think it is a bit misleading to just say that it "turns on". I suggest to have this checked by other people - I would be very curious to see a follow-up on this. You are actually tempting me to try this out in my own lab.
Anyway, even if it turned out you had slipped on this one, that does not change my opinion about your work. Physics is non-trivial, and what really matters is to have the right scientific approach to problems, not to never ever make a mistake (even Galileo did) - eventually things sort themselves out if you follow the right track.
I would really appreciate if you try it in your lab.
I agree that physics is non-trivial and that anybody can make a mistake. But I'm a little disappointed by the lack of experiment. The thought experiment is a good idea, but a real experiment can show that you are right or wrong, and that is extremely important in the scientific method.
PS: to be clear, the reason for the effect not being immediately "complete" is that, although the energy does propagate through the fields and not the wires, the fields do not reach their final configuration until the other wire also settles in the final configuration, that happens only after several back-and-forth along the long wires.
One variant to this problem is move the switch to the other wire, next to the light bulb - what do you think would happen in that case ?
Yes I also think Derek has made a misconception.
When the DC current flow is stationary many seconds after switch is closed, then the magnetic fields of the long folded wires cancel themselves out because of the symmetric current. There is no statc field either on the outer wires since they are on the same voltage potential and the resistance is defined 0. So In the end there is a resulting energy flow actually over the short distance battery to bulb. So far so good.
But as long as we have a switching event, the fields need to establish, and this takes time with the speed of light. When switching on, the voltage potential change on the wire end triggers a wave traveling along for one second until it reaches the bulb. However I am wondering if this argumentation can still be done while assuming the impedance, thus capacitance and inductance of the wires to be 0. I feel this is contradicting and at least a non-zero inductance is needed.
I love to see comments like this.
Healthy discussion about science. Awesome stuff
Another important thing worth clarifying is that prior to the switch being closed, we have to assume that the system is in a steady state with a buildup of opposite charges on either terminal of the switch (if it wasn't in a steady state, then the light would already be on). When the switch is closed, current starts flowing (which sets up the magnetic field and radiates energy as discussed in the video), but it starts flowing at the switch and not at the battery. The battery doesn't "know" that the switch has been closed until the Poynting vectors from the switch reach the battery. So it's really the distance between the switch and the bulb that determines when the bulb first experiences any current, and not the distance between the battery and the bulb.
Yeah you are absolutely right
Yeah this is a huge piece of the puzzle. The "event" in this case is the switch flipping, so for causality purposes it's the switch-to-bulb distance that matters.
Is this true cuz that’s makes so much since. Or is it like what he said in the video the energy is going from the battery to the lightbulb directly through the air? What would be the case if the light bulb was intact 1/2 light year away but the switch stayed close. Alternatively what if the switch was 1/2 light year away?
@@TraxxasJr causality alone should make it a 1/2 year delay at the shortest in that case.
That makes more sense to me. I figured there would be a buildup of charge at the switch, and that the system could be simplified to electron source -> bulb -> switch -> electron sink, and it didn't matter that the source and the sink were at the same point. Only the fact that the bulb and switch were close together mattered.
It led to another thought experiment: what if there were two switches at the battery terminals that turned on simultaneously? To me, it made more sense that the electric field would need to propagate along the path of the cables, and only once it reaches the bulb (halfway) do electrons actually begin to flow along the electric field, creating the magnetic field. There is no Pointing vector without the magnetic field, and thus energy cannot flow until that electric field has fully propagated along the entire 2 light-second path (though it propagates from both ends, so it would take 1 second).
EDIT: Then again, what happens when the battery is a light-second away from the switch-bulb combo? Close the switch and the bulb is close, yes, but the battery has to somehow send energy 1 light-second away to the bulb. Would the energy have to travel for that full second? Or is there already energy that's "stored" in the existing, nearly-complete field?
Amazingly fast wave function. Perturbation is the way I understand it not a point a to b. Just like a wave those particles of water are not traveling the distance of the wave. They are perturbed by the ones next to each other on down the line. The energy of time is also moving in one direction... We can theorize more direction but not one human has experienced time moving backwards.
he just made it more complicated to understand!
simple explanation:
positive & negative electron meets then it creates energy.
This is another example of faulty explanations that many of us have been taught. In other reply I gave you some directions where to look for the (mostly) correct info.
I’ve been an electronic technician since the 90’s and I remember one of my electronics instructors explaining this to us and it still blows my mind all these years later. Fascinating video, thank you for posting.
Suppose the bulb in the diagram was at the middle of the top line of the square of wires would the field arrows that were in the diagram still move towards the lightbulb?
I think it is a bit easier to picture when thinking about microwave Radio Frequency (RF): they literally have wave-guides that look like steel pipes. From the shapes of these "pipes", it is clear that all the energy is in the empty space inside the "pipe" rather than in the conductor on the surface.
I am not convinced. I think the E field needs to propagate along the wire to have enough intensity to light up the bulb. Otherwise, if I disconnect the bulb from the wire, according to the video, it seems the light would still be on, which cannot be right. Would you might help me understand this?
Can you explain something? When I switch my house light on, what distance is taken into equasion? From lightbulb to nearest transformer?
@@Megalolio From the switch to the light.
It's great to see the Poynting flow argument reaching such a large audience! I always cover this in my college E&M classes. But I have to say that the claim that the light bulb turns on right away is pretty misleading. Consider the case where the circuit is actually open -- somebody cut the wire 300km away. By causality, the light bulb's behavior is identical in both cases (closed and open circuit) for t
Yeah, this video is really misleading in the way it presents the flow of energy through fields as a result of varying voltage as the main way that energy is transferred through the circuit. Not to mention that the "electrons move really slow" things needed to be elaborated on, in both DC and AC it is a chain reaction not too unlike a newton's cradle that moves the electrons further away and transfers the same potential (Voltage) to them.
The electrons carry the potential to do work and then as they flow they lose that potential and regain it as they pass through different systems. I feel like this channel has been focusing more on being shocking then actually properly explaining the subject matter.
@@CrystalLily1302 no, the pointing flux part is fine. The em fields definitely carry the energy. The problem is with the idea that the light bulb "turns on". Just a language issue, not a physics issue
@@CrystalLily1302 agreed
@@SamGralla it IS a physics issue. the energy the light bulb gets after "1/c s" (whatever that is... it's a meaningless quantity and hurts my eyes as a physicist and teacher) is way lower than what it gets after some seconds (not just 1). because the energy travels through the fields, but the fields are established by the current. and they travel as a wave (slower than c!!!) along the wire when it is switched on.
to really let the bulb glow that fast he would have to use an incredible high voltage battery.
Adding onto this, the Poynting vectors shown in the illustration are the steady-state vector field. They do not reflect the reality of the EM field during the transient period as the circuit reacts after the switch is closed, which is what needs to be considered to answer the question.
When one does consider the transient state, the result is that some small transient inductive currents do appear at the bulb, but the net power flow into the bulb remains essentially zero for the first second. Only after the change in voltage propagates from the newly-closed switch along the wire all the way to the bulb, do we finally see a persistent voltage drop across the bulb, which produces a steady current and hence a net power flow into the bulb.
Furthermore, even just looking at the Poynting vectors from the illustration, the vast majority of the power flows along paths very close to the wire. So if we consider the opposite question, “What happens when the switch is turned off after it has been on for a while?” we get the answer, “Energy is still flowing along Poynting vectors close to the wire for an entire second after the switch is turned off, and a small amount of extra power continues to follow even longer paths in the space beyond, so the light stays on for at least a second after the switch is turned off.”
there is but one more question that i need to know, twisted pairs are used to lessen the amount of power of the magnetic field to transfer data without any loss, or least amount of loss. but if energy gets transferred or rather data in this point, how does it not go away in the lessening of the fields, or now that i think of it, should we not get a pinch or snap when placing a hand close to a wire? since we are in the magnetic field of the wire. i do believe you , since you had plenty of backing up to show it. but it did leave me with some questions
Amazing explaination of such a simple phenomena which textbooks do a deservice , kudus to that amazing idea of poynting vector.
A fraction of the energy passes through the fields directly between the source and load, and another (larger) fraction passes through the fields near the wire. So in the idealized case discussed in the video, a small amount of energy passes through the air, and that's enough to light the bulb. For most realistic circuits with relatively short and widely spaced conductors, the amount of energy passing through regions of space distant from the wire is pretty much negligible, particularly since most realistic systems have a minimum voltage/current at which they'll activate. The answer in the video is only correct under the assumption that ANY non-zero current is sufficient to light the bulb.
If the bulb in the video required a minimum voltage across it that was some fraction of the battery voltage, then it wouldn't light until a sufficient fraction of the energy from the battery arrived at the bulb. Most of the energy travels very close to the wire, but there are also paths directly from battery to lightbulb, as well as paths that follow near the wire partway and come back near the returning wire. So the voltage seen by the bulb will gradually increase as energy along each of these paths reaches the bulb, with the full voltage only showing up when the fields travelling very near the surface of the wire arrive (~1 second in the setup in the video where the wires are one light-second long from source to bulb).
Yes ! Such an hypothesized light bulb would just light-up anytime you get it near a cable with AC going through it... This is an abusive hypothesis.
Yes, Veritassium is wrong in this case.
So you are saying that if I took a magnifying glass and drew dense field lines very very close to the wire most of the energy travels through that all the way?
Yes, exactly! Veritasium essentially just showed as that a nano-Watt of power will radiate instantaneously as if the light bulb is the receiving antenna of a radio. Totally not what his question was framed as asking!
I completely agree with you, I feel like the question is misleading and the "correct" answer is only valid for a very small distance between the source and bulb. The wires still serve a waveguiding function and the vast majority of the energy propagates along them.
I think one of the most difficult things about the Poynting vector is to visualise the cross product in your mind. That video with all fields represented in space is extremely helpful and should be shown in EM courses.
The poynting vector visualization is wrong though! Vectors are much closer to the wires. Unfortunately a misconception in this video
@@marvinalbert not wrong, just not 100% to scale is what you meant.
@@isaacgroen3692 Actually arrow directions are pretty wrong, they're much more parallel to the wires.
The vector isn’t a real thing, it’s just a mathematical device.
Once again I remember why I nearly failed E&M in college.
Energy running outward perpendicular from conductors was always obvious to me for some reason. When you go fo touch your hand on a live wire, you can feel the EMF before your hand touches the insulation around the wire.
Also makes sense that energy would have to travel laterally from a source - pretty sure that is how we diagram all sorts of things that are branches and you see the same thing to some degree in nature eg actual branches
A QUESTION: As an engineer. I am well experienced in thinking about RF propogation in terms of Electric and Magnetic fields but I guess I never thought about a simple DC circuit this way. Capacitance in cables is also a standard practical engineering issue. But my question is, suppose you encased the battery in a thick metal RF shield that would prevent any EM radiation passing through... would this reduce or stop the energy flowing?
If your load is connected via wires that lead into the container it probably wouldn't be affected, the wires act as field guides as they are quite literally field reflectors.
As an electrical Engineer who works in a transmission company, this video explain the basics well
Username doesn't check out.
Thanks for the fact-check. I sometimes feel like these big YT'ers are just yappin nonsense lol.
@@samsonsoturian6013 Lmao. Good spotting.
Ok
i'm studying electrical engineering and this video is just confusing me
3:40 I've always wondered about this part - the electric wave is at max amplitude in sync with the magnetic wave. I would have thought they were offset - so that the sum of both of them added up to the total, and it was kinda like a chain where it alternates between the two.
Depends on the phase angle, in this animation they're at a phase differential of 0, it can be 90 or even 180 degrees out of phase depending on circuit configuration. At 180 is when the power is purely reactive.
I want to add one correction, energy is oscillating between source and load @ twice of the source frequency, now due to load resistance ( representation of energy conversion to nonelectrical domain from the electrical), the average of the poynting flux is absorbed in the load.
I have studied electrical engineering for four years. I finally understood why we as an engineer sometimes needs to approach a problem in scientist way. We are just applying some formulas without digging deeper to the profound concept of understanding.
Yeah the electronics engineering courses I took gave Maxwell's equations the same cursory treatment. It annoyed me so much that we only covered the 4 commonly cited ones while there are actually more to his work.
It's astonishing to me that people can use math to engineer (successfully) without understanding the core physical reality of how it works.
There are aggregates of inprinted sheets of papers glued together we call "books",
you can purchase this kind of stuff or borrow them in various places on this planet.
generally they come in different sizes and contain informations on the subject of your choice.
you will be surprised, if you read some early electric motor sheet paper aggreagate, to find out that there was not a single innovation in this domain in 100 years, and all of the discoveries on this topic were made by one dude named N̶i̶k̶o̶l̶a̶ ̶T̶e̶s̶l̶a̶ Elon Musk.
@@josh__mclendon that's how engineering is taught unfortunately.
In electrical engineering, power system for long transmission line, voltage and current are assumed to be traveling as an electromagnetic wave, but never knew time for transmission depending upon the vector displacement between source and load.
With such a long wire, how do the fields "know" where to go? How is it able to transmit energy immediately, but a disconnected lightbulb another meter away wouldn't power on? (or maybe it would?) In fact, how does current "know" to start flowing when the circuit is complete?
Or what would happen if you cut the wire at one of the tips? Would the field instantly start receeding everywhere? 1/c seconds to turn off?
Exactly this. I need answers.
That's the best question.
You need a conductor to propagate the EM-field.
I think it would still turn on because we effectively have two antennas, one at the battery and one at the bulb.
Yeah, I think he's wrong on that one. With no wire to guide the waves, the light bulb wouldn't feel the source.
If you want a more detailed simulation see the video I posted after he posed the question the other day. I can simulate your alternate scenario as well if you'd like!
Curious in this example unhabe the batter about a foot.from the bulb. If what your saying is correct would the distance the battery is from the bulb change anything? If the length of cable stays the same would the distance effect anything? And if the power is flowing thebwaybyouve shown its kind of mind boggling .. almost like the actual power is wireless in a way? What happens when say a human walks through the field between the battery and the bulb? Wouldnt thst change things / intrrfere with the process? Would love a response. So intriguing. Cool video. Makes sense but also very hard to comprehend givin the way we are taught to see it. Awesome sauce 👌
But if they 13:17
Your statement is confusing if the magnetic field are the main thing which is delivering the electricity then what is the use for the wires.....
This is a doubt that will arise with people who do not know clearly what is happening...
If I am correct, it is like this,
For magnetic field we also need moving electrons and for moving electrons we need wires, the electrons move because of high potential and low potential but the energy is transferred by the magnetic field.
I hope this is correct
I think the best part of this video isn't just the information it presents, but also the conversation it sparks in the comments! People asking questions, people trying to understand what's being said, and even people providing counter-arguments in certain scenarios where what Derek explains doesn't seem to match up. I think having civil discussions helps a ton, thanks Derek + the Veritasium community! This video and the comment section is genuinely interesting to go through
People just figured out that he is wrong 🙂
@@markmd9 where's your evidence?
I think he is being somewhat intentionally deceptive/vague in the video on purpose to cause this :P
He's not wrong, it's just a weird perspective.
I'm wondering if you even watched the video before you posted this self-aggrandizing waste.
@@markmd9 He is partially correct and partially wrong. There will be some small energy transfer between the bulb and the battery in 1/c but the bulk will happen after more than 1s.
Speaking as an electrical engineer, electricity is the closest thing in to magic that everyday people deal with.
I deal with conceptualizing electricity and electrical components every day, and you're kind of forced to think of amperes like your chain analogy, voltage like water pressure, transformers like gear boxes, etc.
But you have to keep in the back of your mind the whole time "but it's not water mains or a gearbox, it's electricity". It's simple up close but a whole other different thing when you try to think of the whole power grid at once.
My advice to laypeople? Learn what you can, and marvel at the physics of electricity with me! ...But call a professional if you need to wire a car charger into your garage.
word!
I can almost guarantee that the electrician who wires your car charger doesn't understand much of this either >
@@nathan87 electrician here; we’re not labourers or handymen, we’re trained in electrical theory and hold technical qualifications. We may end up slightly dirty at the end of a work day but we’re well paid and quite knowledgable 😊
I am exactly the kind of person the wise man was referring to when he said "A little knowledge is a dangerous thing". I'm exactly the kind of person who would learn the basics and immediately think they could DIY their own car charger, lol. This video, and indeed this comment, are good reminders that I don't know ANYTHING about how electricity works, no matter how many cool analogies I know.
@@nathan87 But he will certainly be aware of the dangers evolved with working with electricity! As the OP already quoted, electricity comes pretty close to magic: you can't hear/smell/see it, but it can kill you quite easily.
Excellent video and explanation.. now I’m wondering how over current protection really works if it’s not the current delivering the energy?
Current is the Magnetic portion of the field and Voltage is the Dielectric portion of the field. Most over current devices don't sense current itself, but the strength of the magnetic field. When you want to know how much current is in a wire you use magnetism to gauge it. With a hand held meter or with a Ampmeter on the switchgear/bus itself. You are not actually measuring current, but the field strength that is directly related to the current needed to produce a field of that strength.
So to answer your question energy doesn't flow in the wire and doesn't need to because we don't have devices that measure the current anyways. It measures the field around the wire. And that field will tell us the amount of current. So if current goes up, the field increases and the current Transformer that is wrapped around the bus bar or wire will be induced by the field, step it down to a few amps, and say the amps go from 1 (normal) to 5 then your over current device will "trip" if it is set to trip at 5x the normal current rating. Hope that makes sense.
After two years of electrical theory in 1975,6, I wish I'd continued learning this exciting theory.
I have a degree in Mech Engr and my Physics E&M class was the only class where I was like “yeah I just don’t get this”. Sometimes I’ll wonder though if it really was that bad. This video just reminded me that yes, yes it was that bad.
yess @clarierich my whole Electrical engineering is flushed today....
it's interesting to get this phenomenon....
please clear my some dough ...so i can better understand this.
so what we checked in ampere meter ....
what is the meaning of current raised ...
so how battery ..drain,
why conductors overheated ..when current raise..if electrons doesn't flows...
We keep the energy away from the conductor, it must not flow there, so we coat the conductor with isolation to keep the fkrs out@@lalitjoshi7152
I'm also an EE and I just got stumped. In a few minutes all my knowledge is getting jumbled up in my brain.
@@lalitjoshi7152 please clear my some dough ...so i can better understand this.
@@lalitjoshi7152 Current needs a complete circuit to flow, in a conventional circuit, it's basic Ohm's law. Open circuit = maximum voltage, zero current. Closed circuit = maximum current, zero voltage.
Negatively charged atoms (determined by electron surplus so we can say electrons instead) repel each other along the conductor in which they're present, this is why a thin wire cannot carry a large current - electron density. There's only so many electrons in a small space. In doing so it generates heat and yes, current flows. See my post below for where I believe this video gets it all wrong. The same electron as given by the battery is not the one that appears instantaneously to light the bulb.
You in line ammeter is measuring electron flow, just how you think.
Battery is drained by having free electrons removed, just how you think. It's energy was needed by the device in question to produce either heat or light or both.
Conductors overheat because of electron flow, just how you think.
Until I see good reason otherwise, I consider this video incorrect.
Holy crap. I have degrees in engineering, have investigated numerous electrical fires and worked for decades developing electro-mechanical devices, and no Electrical Engineer has ever explained electricity this way. Things now make a lot more sense.
His explanations are trivial, and answer to light bulb problem is absolutely wrong.
@leonidfro8302 source: "trust me bro"
@@leonidfro8302nah its correct and you just dont understand at all
@@variamente6855 The question is asked in highly misleading manner. There's no "misconception", Maxwell equations are known and taught in 2nd semester of engineering degree.
@@leonidfro8302just because they're taught clearly doesn't mean their implications are understood. As you're evidence of. Most people in these comments have studied engineering, as have I. Over a decade ago.
OK, you say that electrons are not flowing through wires. So, why does a vacuum tube have a cloud of electrons floating in it ? Where are these electrons going, and are they not flowing ? Then semiconductor material is doped with either extra electons or an shortage of electrons. The models for thse, have shown us electons flowing. Are these models wroing, and if so, what is happenting ?
Anyone who enjoyed this video should download and read a copy of Dollard's 2 papers "The Electric utility in the digital age" and "Revival of the science of Electricity in the Digital age" really eye opening stuff.
"The harmonic malady was propelled forward by a shift in reasoning, this from the established viewpoint of electric transmission as an electromagnetic boundary condition (Maxwell-Heaviside), to the modernistic viewpoint of electric transmission as an electronic current (Lorentz-Einstein). In the modern viewpoint electricity was no longer propagation in the space enclosed by the transmission conductors, but the notion is that electricity is propagated within the transmission conductors themselves. Accordingly, in this view, the space surrounding the transmission conductors is void of any electrical activity. This mindset has made impossible any understanding of electric transmission and has sent electrical engineering back into its dark ages when electricity was regarded as a material substance."
Eric Dollard definitely has the best understanding I've heard of when it comes to EMF transmission and generation.
This is basically transmission line theory (I'm an electrical engineer who specializes in this, in electro-magnetics). You can view the two lines connected to the battery as a dipole antenna, same for the lines connected to the lamp, and that the two antenna's are shorted at the ends to one another. These antenna's operate in near-field. Another way of looking at it in this particular case is that a capacitor is formed between the lines connected to the battery and the ones connected to the light-bulb. I do not agree however, that the circuit behaves as you said it would, the power transferred should be in the order of milli- or micro watts which is not large enough to cause the lightbulb to glow visibly as it would require tens of watts, you should put it into an electromagnetic simulator to calculate the exact power transfer.
The "light bulb" is really an idealized current detector which consumes no energy from the system. Thus, even if just a nanowatt is transmitted to it, the "light bulb" comes on instantaneously at detectable brightness. Obviously real electric light sources do not behave this way, but this is a thought experiment.
Thank you for this explanation, I was totally lost on his explanation until you mentioned that these lines are acting as (near field) antennas. Otherwise I was lost in the weeds trying to figure out how you could shortcut a transmission line's delay.
I'd like to see more explaination about the antenna/near-field thing, I think that's missing in the video. Together with a diagram of a more complex, less geometric ideal, power transmission.
@@killerbee.13 Random noise sources want to have a word with this thought experiment
You will need time that enought to energy transmitted by resistanceless antenas of certain lenght to light a bulb. So you will need (x+1)/c or 1 which is smaller, seconds there the x is length of antenas required to generate power to light the bulb. Possibly it will be already shine if x is smaller than c/4.
As an electrician, a very curious one who always has to dig deeper into the why and hows of life. Im aware of the concept. Ive never met another electrician that understands or believed me. Great video.
Well, not to say that you’re wrong, but I too have thought this and I’ve been an electrician (now retired!) that thought I was the only one of us to believe it. Where’s Nikola Tesla when we need him???
are you hiring?
Hey, I'm about to start my apprenticeship as an electrician!
@@WyrGuy2 i didn’t say they didn’t exist, i just stated i hadn’t met any of them. Now i can say that i have. Nice to meet you. Tesla was a crackpot… an absolutely brilliant mind that i feel had more discoveries left to share with the world.
@@null-00000 i think its an amazing career. I wish i had started right out of highschool
The conductors are connected to the battery and fully charged, so when the switch is closed electrons don't have to flow 300,000 kms. Connect positive and negative terminals simultaneously on the battery and see how long it takes for the bulb to light. The conductors are already full so the electrons don't need to travel. Turn the faucet on for your garden hose with an empty hose and wait for the water when the sprayer is opened then try it with a full hose.
Hey I’ve got a question? What happens when the wire is twisted, does the energy go through it quicker where it’s twisted or do the magnetic fields naturally go all the way down the wire and then to the light and if so why, natural currents tend to find the easiest path to the direct source so what happens?
They don't take the "easiest" path or the shortest path. These are misconceptions. They follow the path of "least resistance". A cable can be 100ft longer but with less resistance and electricity will take that path. Well it takes all paths at the same time tbh. But it prefers the path of least resistance.
And do you mean one wire being twisted? Or if 2 wires that are energized are twisted? And Electricity will always follow the wire. He confused people with the bit where he says it will get a little power at first instantly then full power a second later. He is talking about induction. Which is not really the same as transmission.
What a perfect name Poynting had so that his vector points in the direction of energy flow! Reminds me of how the Schwarzschild radius for a black hole was calculated by a physicist whose last name means "black shield" in German.
Right? When I first taught about the Poynting vector, I thought my professor had said "pointing vector", and he had to spell it out haha.
That way he wouldn't end up disappoynting us
Bruh i speak german and i never realized that
Nominative determinism
Yeah. I laughed at reading the name. It's like an unintentional pun.