HN Theater @HNTheaterMonth

> Anything involving the electrical energy not inside wires has no water analogue (ie the electromagnetic waves inside a transformer)

You don't even need fancy things like transformers for energy not in the wires to be important. Even a simple DC circuit consisting of a battery in series with a light bulb mostly involves an electromagnetic field to transfer energy from the battery to the light bulb, which mostly takes place outside the wires.

The function of the wires when it comes to energy transfer is to carry moving charge which creates the magnetic part of the electromagnetic field that actually carries the transferred energy.

Here's a pretty good explanation [1]. That video was from January 2019, and not controversial. Veritasium did a video on the topic in late 2021 that didn't really present things as well and ended up being quite controversial [2]. Other well-known YouTube channels such as EEVblog [3] and ElectroBOOM [4] responded.

There was also someone who bought a bunch of wire and did the experiment as described in the Veritasium video (although scaled down). That was discussed on HN and that discussion contains some very interesting links [5].

In particular the link to a talk by Rick Hartley in this subthread is very informative [6]. He talks about how most EMI problems in PCB designs are due to people not taking into account the the energy is not in the wires.

[1] https://www.youtube.com/watch?v=C7tQJ42nGno

[2] https://www.youtube.com/watch?v=bHIhgxav9LY

[3] https://www.youtube.com/watch?v=VQsoG45Y_00

[4] https://www.youtube.com/watch?v=iph500cPK28

[5] https://news.ycombinator.com/item?id=29598860

[6] https://news.ycombinator.com/item?id=29601273

⬐ gaze

The thing is that KVL and KCL hold, and KVL and KCL hold for both electrons and water. You just have to not think too deeply about what motivates the electrons to move. Current is indeed the mean velocity of carriers through some area, and voltage is mmm... well it's related to the electric field. It's just not exactly fluid pressure even though it behaves as such.

The right way to think about this if you _really_ care is a bit like the way that RF engineers think about dielectric resonators. The metal motivates the fields to be guided along pairs of conductors by the motion of charge carriers within. A metal will respond in a particular way to fields, which results in new fields, and so on and so forth in a way that results in the fields propagating along in a particular way.

A propagating pulse is a bit hard to think about but you can imagine some field configuration that results in the electrons in the metal slipping a bit, and those electrons move in a way that results in new fields which contain the new wavefront of the pulse. The electrons don't keep moving -- they move on average the distance of the mean free path and give their energy to the lattice as heat. This is why the drift velocity is just a meaningless number. The fields propagate at around c and the conductors guide them.

The term 'transmission line theory' (or even 'transmission' for that matter) doesn't appear to have been mentioned in the video at all[0], and this is a complaint that was also raised by Dave Jones[1] in his critique of sorts. The video is fundamentally about transmission line problems and the term is mentioned both in the description and the word document containing further analysis, but its omission does lend some credibility to the complaints in the parent comments that the video style is intentionally pedantic (it is a pure physics vs practical electrical engineering take after all) and presented as a controversy which comes off as a bit shallow as a result.

If one were to put on a tinfoil hat it doesn't seem like much of a stretch to imagine that the plan was to have a follow up video to settle the controversy with the gist of the video being about transmission line theory and concluding with a practical demonstration of the effect.

[0] I don't have the time to carefully watch a 15 minute video to verify this, and demonstrating a lack of evidence seems difficult, but the subtitles for the video can easily be downloaded with youtube-dl and then grepped or opened with a regular text editor. Note that these subtitles are manually written and not auto-generated by youtube, and while it's possible there's some differences in the script and what is said it seems unlikely.

youtube-dl --write-sub --sub-lang en --skip-download https://www.youtube.com/watch?v=bHIhgxav9LY

grep -i 'transmission' 'The Big Misconception About Electricity-bHIhgxav9LY.en.vtt'

[1] https://youtu.be/VQsoG45Y_00?t=1013 (16:53)

EEVblog goes into depth about the video, basically calling it out and explaining the how and why the headline is misleading.

https://youtu.be/VQsoG45Y_00