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interested to hear other hams and ee types' opinions on the Veritasium video

i think it's basically not useful as an educational tool despite being technically correct

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@tindall In the beginning it says 1/c seconds but that's not even a unit of time...

@x44203 what he means I think is distance/c where distance is the separation between wires but that's... Not explicitly said at any point

@tindall Also it is possible to transport electrical energy without most of it being in electromagnetic fields

@tindall Well, I guess cables have too many electrons and obstacles for that

@tindall OTOH that way you can reach much higher power densities, current devices reaching about 8 TW in a few cm large pipe

@tindall Hmm, in a pulse its apparently about 270 ZW/m²

@tindall Back to the video: He says that the charge on the surfaces of the conductors make the electrons move, but isn't that rather caused by the charge difference between the ends of the wire? I guess the surface charges would conform to that

@tindall Hmm also uhh I think the thing with the bulb is plain wrong unless you define that on = "some non-zero amount of electromagnetic field is present", at least with the pictured wire sizes

@tindall In my simulation it would take multiple seconds for the bulb to get any level of brightness

@tindall This is a very rough approximation, I used 20 ohm for the bulb and 200 ohm for the long conductors (and the side stubs 50 ohm at 1 ms cause LTSpice would take a long ass time if they were 4 ns)

@tindall Ohh, also what about the conduction in human nerves? Thats pretty slow

@tindall Wait, did he just invent FTL? The information that the loop is closed should take 2 seconds to propagate around the wire to the other end of the battery.

Or is it just the part where it's better to look at it as a radio engineering problem, in that this would work (the lightbulb would receive some energy) even if the wires were cut some distance away, or the switch was just moved (but not closed) 100 meters away - because those wires act as antennas?

@tindall nah, I suppose it's too late in the night for me to figure this out.

I'm leaning towards the answer being "D/c seconds before energy transfer starts", where D is the distance between the lightbulb and the switch - because that's the fastest it can take for the EM field induced by the switch (which suddenly makes the "antenna" longer) to propagate to the lightbulb.

I'd love to see the plot of how the power received by the lightbulb changes over time in those first seconds.

@tindall That would also imply the video is extra confusing by placing the focus on the battery, where it's the position of the switch that matters, because that's where the EM field is first created.

So: if the battery was on the Moon and the switch next to the bulb, it would light up (ever so slightly) instantaneously; if battery was next to bulb and switch was on the Moon, it would light up after ~1.25 seconds.

Any way I look at it, it's either that or he invented FTL communication.

@tindall what’s interesting that RF (also an EM field) traveling in a transmission line is always slower than the speed of light. In fact transmission lines have a characteristic velocity factor Vf that is a percentage of the speed of light.

en.m.wikipedia.org/wiki/Veloci

And obviously RF traveling through free space does not exceed the speed of light.

So no FTL communications based on this. Try quantum entanglement perhaps 😀

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