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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]

#91

Post by MarkusWandel »

Light is slow, not exactly 1 foot per nanosecond but it's a reasonable mnemonic. Think about that, if you had an optical cable running a reasonable (these days) 40 Gbits/second link and it's 3 feet long, that's 120 bits in transit from end to end at any given moment. And that's if it is optical and ignoring the slightly slower speed of lighit in glass; any sort of actual wire is slower.

For a transmission line i.e. one limited by distributed inductance and capacitance, the standard practice is to drive a powerful transient into one end, which then travels along the wire, switching any receivers along the way, and then absorb it in a termination resistor at the other end so it doesn't bounce back and glitch the receivers on the return trip. Again you have to consider an actual traveling wave; there's no such thing as "instant" on a wire of any length.

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

#92

Post by yholio »

TLDR: Veritasium is wrong and misleading, current actually flows in wires and is the main way energy is transported from source to the consumer, energy does not generally flow in the space "between" the wires.

Yes, very long wires behave like capacitors/antennas and transmit a certain amount of transient power instantly by coupling, but most useful energy is transferred after the speed of light delay, when steady state is achieved.

Nonetheless, by carefully selecting the AC frequency and the physical configuration of the lines, you can create a situation where most energy is transferred nearly instantly by the electromagnetic field and the far ends of the line are more or less irrelevant. So you obtain the Veritasium effect, but it's a very particular arrangement, not the general case.

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

#93

Post by haberman »

tpush wrote: post #76

So, I genuinely do not get the "controversy" over the Veritasium video. AFAIU, the entire point of the video was to show that electricity travels not through wires but via electric fields ("through the air" so to speak). To illustrate this, he sets up an experiment with parameters such that the conclusion can only mean that some electricity has traveled to the bulb before any could arrive through/around the wires. He…

If electricity doesn't travel through wires, why do resistors dissipate heat?

I'm having trouble understanding what is even being claimed. Electrons are moving, without the movement of the electrons there is no electricity travel, without the wires there is no flow of electrons, so what does it mean to say that electricity doesn't travel through wires?

Is the claim just that the electricity, by way of fields, travels at a rate much faster than the electrons themselves are traveling? That seems like a reasonable claim. But "electricity doesn't travel through wires" seems rather suspect.

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

#94

Post by Pulcinella »

colechristensen wrote: post #3
csense wrote: post #2

I'm a big fan of AlphaPhoenix's content. He deserves to be in the big leagues of science YouTubers with SmarterEveryDay, Veritasium, Mark Rober and 3B1B.

I’m not a fan of the “big leagues” of science YouTube, many seem to have been tainted by the attention algorithm game.

Agreed. I’m especially disappointed with Veritasium because Derek’s originally PhD thesis was how these sort of “controversial,” clickbait-y popular science videos are actually really terrible at teaching anything.

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

#96

Post by gcommer »

tpush wrote: post #76

So, I genuinely do not get the "controversy" over the Veritasium video. AFAIU, the entire point of the video was to show that electricity travels not through wires but via electric fields ("through the air" so to speak). To illustrate this, he sets up an experiment with parameters such that the conclusion can only mean that some electricity has traveled to the bulb before any could arrive through/around the wires. He…

There's two bits of controversy:

1) Slander: He claims that the way EE is taught is a "lie" but leaves out the many ways that standard EE models agree with his result.

2) Clickbait / inadequate explanation: he leaves out many details in order to make his experiment seem far more mind-blowing that it really is.*

Critique 1 can be countered by saying he is targeting a lay audience (say, they took 1 high school physics course).

Critique 2 can be countered by saying he is targeting a slightly more advanced audience who would understand those details (say, 1 or 2 college courses).

But no matter who you think he's talking to, at least one of these critiques holds.

* In particular: a) He doesn't explain how "1/c" is derived from the 1m gap. b) He portrays the electrical field as totally detached from the layout of the wires. But if you rearrange his lightsecond-long wires to be a circle, the effect won't happen. c) He leaves out the fact that this experiment works even if you cut the ends of the wires, which would change many people's intuition (think of the wires more like antennas). d) His thought experiment is actually wrong: see Electroboom's video, but basically by Derek's own parameters the light would _always_ be turned on.

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

#97

Post by foxfluff »

soneil wrote: post #58
sega_sai wrote: post #51

Earlier quoted context omitted.

I just arrives through the air. The electromagnetic wave will propagate with similar speeds through the air and wire.

I didn't finish the video (yet, no fault of the video, just bad timing), but I don't think it's EMI - the "pre-current" looked fairly flat, and EM doesn't like flat. I'd expect EMI to show as a spike timed to match the leading edge of the signal.

I think the takeaway is that EMI looks flat for a while if you run half a kilometer of wire next to a half-a-kilometer long source of EMI.

The leading edge isn't there for one nanosecond and then gone, it travels down and continues to induce a current to the adjacent conductor, a current which must continues to flow.

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

#98

Post by kzrdude »

tpush wrote: post #76

So, I genuinely do not get the "controversy" over the Veritasium video. AFAIU, the entire point of the video was to show that electricity travels not through wires but via electric fields ("through the air" so to speak). To illustrate this, he sets up an experiment with parameters such that the conclusion can only mean that some electricity has traveled to the bulb before any could arrive through/around the wires. He…

I think "the point is being missed" in the Veritasium video, because it is obscured. It's obscured to increase the "gotcha and unintuitivity factor". Veritasium more or less makes it sound like all the interesting parts of the circuit goes through the direct line-of-sight path between the battery and the light bulb, and ignores the wire. Which is misleading.

Derek would not have written tweets like this one, if his video had been more direct about what he was talking about:

https://twitter.com/veritasium/status/1462115954775654405

"Basically yes - you can think of it like two antennas"

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

#99

Post by Jansen312 »

TempestSA wrote: post #35

Why wouldn't a simpler explanation be that the wires produce a radio/electromagnetic wave and that wave gets picked up and induces a current, which is how radio transmitters receivers work?

Most people didn't have EE education at college level. Transmission line or radio wave carrying energy is a concept usually taught much later in ones schooling. Derek basically want to target mass market that receive basic electrical knowledge that actively tells you electric "only" flows in cable. A lot of people replying to his video subsequently demonstrate that Derek is right that these group of people have the not exactly right idea taught at school. Some people replying wishing to show he is wrong completely missed his message.

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

#100

Post by it_does_follow »

tpush wrote: post #76

So, I genuinely do not get the "controversy" over the Veritasium video. AFAIU, the entire point of the video was to show that electricity travels not through wires but via electric fields ("through the air" so to speak). To illustrate this, he sets up an experiment with parameters such that the conclusion can only mean that some electricity has traveled to the bulb before any could arrive through/around the wires. He…

> some electricity

I think the key part of the controversy is the word "some".

In the original Veritasium video it pretty strongly implies that enough energy to light the bulb, i.e. virtually all the electricity, is traveling instantaneously a short distance rather than "through" the wire.

A big part of that video is to essentially say you're wrong if you understand electrons moving through the wire as how electricity works.

The video posted here tells a different story which is essentially that the mental model of electrons flowing isn't that far off, but there is a bit of nuance when you take into account fields.

This is sort of a persistent problem with "edutainment". I generally enjoy Veritasium, but this is clearly a case where the education component is weakened in order to increase the "wow!" factor of the video.

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