How Wrong Is VERITASIUM? A Transmission Line Story

Veritasium's answer is both misleading and incorrect. You can forgive the misleading since that's the hook and style used in their videos. But 1/c s is not correct as it is not a unit of time (1/(m/s) s = 1s/m s = 1s^2/m) .. he could have said "1/c m" but it would have given away the trick, but now it's not just misleading, it's false.

Stephen Wilcox

AlphaPhoenix over on Youtube tried it with 1 km of wire and an Oscilloscope. Might be worth a watch for those interested! The title is 'I bought 1000 meters of wire to settle a physics debate'.

Does the wave propagation speed affect things at all? Like would all the answers be modified by the velocity factor of the wire?

Turing Eret

Disclaimer: The following message is a semi rant as this is my intro into Patreon. Yes, I did in fact just sign up and this is my first creator I care enough about to send those $$$. How did I decide? Long story: I don't usually keep up with Veritasium but he pops up on my home page and within my interests so I watched the whole thing and tried to learn a bit but the answer didn't mean much to me. With my economics degree, I easily understood that the assumptions being made didn't really matter anyway because he's conducting a thought experiment, he doesn't really have his own data points to show. Loosen a few assumptions and you can try innovative ways of rationalizing a lot of rather poor decisions made in our lovely market based economics but that's another story. Anyway, luck would have it that Mr. Mehdi here made a wonderful video response. Rather genius youtubing in my opinion, hit all the right spots. The big, Persian man with expressive body language and unapologetically curious/passionate that I see similarities with myself. But why now? Why such a soft spot? Well, let me tell you about Thanksgiving 2021 with my parents (M F 60s) and siblings (M M 30s). For whatever reason, earlier that month, I watched the "metal in the microwave goes BOOM!" video and was inspired by the logic and objective thinking. The multiple tests I watched Mr. Mehdi do on camera was proof enough for me! But then I get the idea to warm a store bought pie in a tin in the microwave, planning to use the dual heat feature of microwave and convection, understanding what I should expect and to keep an eye on it for the "disastrous" arc potential. Boy, did that not go well with anyone else! There was nonsense arguing and the usual Persian man "I will prove you wrong because you're the dumb animal and I have the golden genitals". Any attempt to get them to 1) prove the potential house burning down potential in front of me, 2) watch a YouTube video like they do any other day, 3) admit there are "possible conditions" you can have metal in the microwave, it all meant nothing. You may wonder, well, what's the point? Well, it proved to me that anyone can say anything and they'll do anything to prove that they're right. No compromise, no nuance, it was in line with the Kurzgesagt video about all simplifications being "lies" that we tell children so they can understand that I watched before I was recommended this video. In conclusion, Mr. Mehdi, you are an artist. You have made an undeniably foundational change within me through your art. It's actually so good, I'm willing to pay you to continue doing so! Thanks so much for your your genuine passion and "love at first Persian accent" personality.

Ronnie5545

I saw this video. He mentions that a capacitor is short circuit at DC. However it is the exact opposite. At DC a cap is an open circuit, infinite impedance. Also says that the lines act as primary and secondary of transformer. And that they also act as transmitting and receiving antennas. However transformers, and antennas only work when there is a time varying electric or magnetic field. At DC an antenna cannot radiate and a primary coil cannot induce current in a secondary. I really have to disagree to most, if not all points made in that video

I’m not sure I understand the meaning of “burst of positivity travels at the speed of light”. Positivity is just the lack of electrons. And it has been proven that electrons don’t travel that fast under potential difference. I’m sure these questions may have been asked all over internet by now, saw something similar here too. 1. What if the space within this whole loop of wire is filled with water or any other dielectric. Will the time taken for the bulb increase by a factor of sqrt(dielectric constant)? Coz that’s essentially what is being derived 2. What if the bulb was kept beside the battery. Or on the same line, but 3e8 meters away. Or even on the perpendicular arm of the wire 3e8 meters away? I’m deviating from the main question at hand but I’m not sure if this theory provides an answer to that.

I thought it would be 1/c seconds because of a Mehdi video describing current like a pvc pipe. If the electrons are pushed from one end the electrons farther along are pushed along. My assumption was that the wire already had been loaded with electrons. My conclusion was that when the switch flips the battery just has to push on a few electrons and the electrons at the bulb would pass through turning the light on.

CodyDHarkins

I also thought the same, that his question is tricky and when he gave an answer I thought like "ah, ok, with some omitted conditions..." )

I didn't have the same sort of Visceral reaction, but like... I thought it was off... Now I know why!

J4yC33

hehe! yes!

ElectroBOOM [Mehdi Sadaghdar]

I was triggered by his video too! I am so glad you and Big Clive have made counter videos. Keep up the great work!

Matt Larson

... and diving deeper into absurdity of superconducting wires and supersensitive bulbs. What if we simply *shook the battery*, without connecting anything anywhere? This should also result in moving charges and thus some sort of a super-weak hypothetical EM pulse that can be absorbed by a nearby lamp, right?

Awesome stuff, Mehdi. I like how you don't hesitate to put in very technical details even though its just for youtube.

and how fast *does* current travel in a superconductor? I would assume that even through superconducting material it's slower than the straight-line path of light in a vacuum. why don't you have more superconductors in your workshop, Mehdi?

Kevin Turner

I've been looking forward to this! Oh, that tease at the end though, "What if the lines were giant circles?" because I'd accepted the assumptions of superconducting wires, but it wasn't until I read the attached slides that I realized that a critical part of Derek's scenario is that the wires (antennae) remain a meter apart; that it wasn't only the positions of battery and lamp that are fixed. Another variant on that might be "what if we wrap all this wire into a coil of 1m diameter?"

Kevin Turner

Thank you very much for the correct analysis of that publicity stunt! I pointed out in EEVblog Patreon comments two week ago: "I would say that for about one second, each side of the setup shows as about 800 ohm resistor for the switch and the bulb. That would mean that for 100 ohm bulb the voltage over the bulb would be about 1/16 of the battery voltage." You are the first vblogger I see to point out that the transmission line looks like a resistor until the signal comes back from the far end!

Antti Louko

How characteristic is that impedance?

Reuploaded! thanks

ElectroBOOM [Mehdi Sadaghdar]

His statements are not lies, but half-truths and very shallow summaries which could be interpreted wrong if you fill in the gaps incorrectly; almost like a strawman argument.

Very cool video as always. In case you need more ideas for potential future videos on this topic, note that Derek's answer is badly misleading in: - Firstly, the "demonstration" in the end, where he flips the switch, the lamp turns on and he says that "the lamp will turn on nearly instantly" [in the hypothetical case]. Albeit not saying it directly, he conveys to the viewers the idea that in the hypothetical situation the lamp will receive the full power of a stable state DC circuit instantly "just as what we see now", which is, of course, incorrect. - Secondly, he starts by stating a DC problem and then swaps it up with the discussion of AC effects - that's what the whole "trick" is about, after all. The AC mode, however, enables an even more surprising modification of the problem. Namely, let us take a battery and surround it with 100 of those super-sensitive lamps, not attached to anything. Then let us attach a small piece of that superconducting wire to the battery (also not connected to anything, of course). This should cause a short surge of current which will cause a tiny EM impulse to spread all around the piece of wire. Parts of the energy of this EM impulse will then be absorbed by all the lamps, cause minute current and have them "light up", strictly speaking. Moreover, the EM impulse itself, being white noise, will contain visible frequencies, so we can say the wire itself "lit up" just as well. OMG, right? - And of course the whole claim that "energy does not travel via wires", as stated, is extremely misleading (even if extremely functional) clickbait.

well again it depends on impedances, if the load matches the lines, then in 0.25 second you would have half the operating current and in 0.5 S full current

ElectroBOOM [Mehdi Sadaghdar]

OH DAMN IT! I kept looking and looking and I missed this one! eh... I may have to reupload

ElectroBOOM [Mehdi Sadaghdar]

Oh! The outrage! The sheer impedance of that transmission line! It's got quite some nerve.

Steven J Greenfield

Yes, I have seen a number of people bring up the skin effect, when it isn't relevant to this.

Steven J Greenfield

Except one typo (as mentioned by Aravind), it looks good to me. Very good video Mehdi.

CrouchingTigerHiddenAdam

But as an EE I much prefer your transmission line model. Amazing how many areas this model pops up. It's used in RF engineering and power engineering - both use transmission lines except the frequencies are *very* different.

Michael Mirsky

RSD Academy's video on Derek's video (see https://youtu.be/--v5BXmFYv4 ) is along the same lines as your's. Except he is trying to simplify it more by comparing the wires 1 meter apart as either two plates of a capacitor, or two turns of a transformer or two poles of an antenna so that power flow starts in 1/c seconds.

Michael Mirsky

Some part of it might be confused with high frequency skin effect where most of the current travels in the skin of the conductor

Thomas Eriksen

Meh, I think your observation is a little pre-Mehdi-tatted. Dr. Muller has his doctorate in physics education giving him a reasonable pedestal to stand on. It should be noted that while your observations are not wrong, they do have a significant level of clickbait=bad bias. If your income comes from entertainging people, you would do the same. Keep in mind that it is currently in-vouge to raise a controversial point so that all of the big science YT'ers can rebuttal your observations. This gives all of them an ability to collaborate, retort and defend their views; all things we like. YT creators are entertainers first and foremost followed by educators; their income demonstrates that.

Thanks!! I watched the original video, then EEVBlog's video, and now yours... I think I am understanding a little better now.. I have also reconfirmed my lack of math understanding as a reason I am more happy at sub-mhz logic speeds so I can ignore most of this stuff on circuits I build on breadboards, and that's the reason I took the Network infrastructure route for a career instead of EE! :-) I would love to see the answer about what it would look like if the entire circuit was a 1 light-second circle of wire.. If I understand correctly, since there would be very minimal induced current, it would take 1/2 light second for substantial current to flow?

Steve Jones

Lol love your response!! Minor typo at 69 seconds though https://youtu.be/hNR9B78kX_o?t=69 . 300,00 km.

Stopped watching Veritasium for a while now. I started to feel some bad vibes around Derek... He started to enjoy too much to shock (no pun intended) people, like you knew, learned or believed something and he'll show you how wrong you were. It's right on the edge of clickbait. But the part I don't like now about him is that he's like he's enjoying himself too much by stating his new facts and acting all clever. Reminds me of Mehdi's older video where he explained how easy it is to convince people of your bullshit when you give them well know facts followed by a hard to follow bullshit, people thing "yeah, I know fact 1 and fact 2, I don't know fact 3 but he seems convincing and I could follow the first 2..."

Dukefazon

What about him?!

ElectroBOOM [Mehdi Sadaghdar]

Come on, remember William Osman?

NaturalEnvironment