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I bought 1000 meters of wire to settle a physics debate [video]

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Re: I bought 1000 meters of wire to settle a physics debate [video]

#11

Post by paxys »

0xTJ wrote: post #5

That Veritasium video is one of the most controversial educational videos I've seen. I think one of the issues with it is that it's a bit pedantic, but also ignores other issues, that invites other people to be pedantic about it.

That video perfectly summarizes online discourse. I personally found it fantastic as a resource. It was the best and most clear explanation of transmission of energy in an electrical circuit that I have seen. It debunked a lot of myths in my head that we were all taught in school.

The thought experiment he proposed was just a hook to keep people interested - and it certainly did the job. Because it is a popular internet video by a popular YouTuber, however, the entire scientific community made it a mission to nitpick every detail of that experiment and show that the conclusion wasn't 100% accurate without a bunch of caveats. Which is fine, I guess, but also missing the point of the whole thing.

Re: I bought 1000 meters of wire to settle a physics debate [video]

#13

Post by mikewarot »

jakogut wrote: post #4

I wonder if the results of this experiment would be the same with alternating current?

In the AC world, the wire pairs are transmission lines with a characteristic impedance, and this whole thing can be modeled as a bunch of lumped elements.

Re: I bought 1000 meters of wire to settle a physics debate [video]

#15

Post by wdfx »

everybodyknows wrote: post #6

Anyone care to give us a Too Long; Didn't View?

When you close a switch to initiate an electrical current down some long wires it takes a measurable time before you know what's at the far end of the wire.

Therefore if the wire is either intact or broken at the far end, over a 500m distance the first 1.6us of measurement looks exactly the same.

Re: I bought 1000 meters of wire to settle a physics debate [video]

#17

Post by kleer001 »

everybodyknows wrote: post #6

Anyone care to give us a Too Long; Didn't View?

roughly : electric power (and resulting work) is transmitted at the speed of light in the form of magnetic waves, not by the movement of the electrons in the wire the current goes through

Re: I bought 1000 meters of wire to settle a physics debate [video]

#18

Post by formerly_proven »

It's not really a debate - anyone with basic EE knowledge knows what this experiment does and what few parameters you need to predict the exact behavior.

Of course if you take it literally - superconducting wires, car battery, 12 V light bulb - then it's very likely that the suggested answer is not even technically correct, because the initial pulse amplitude as seen by the lamp is simply too low to light the bulb up. If you take it less literally and match the "light bulb" impedance more or less to the transmission line impedance (~1 kΩ or so in the experiment with the suggested wire spacing and assuming "reasonably thing" wires), then you're getting much closer to the answer he is suggesting.

Re: I bought 1000 meters of wire to settle a physics debate [video]

#20

Post by nathan_f77 »

I don't think it's possible to detect a 200uA current across the resistor immediately after the switch is turned on. If I understand it correctly, then this would mean that information is being sent faster than the speed of light. Surely this small instant current must be caused by some kind of capacitance or interference.
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