How leccy really flows (in the EM field, not just the cable)

This video gives a good summary of how electricity flows in (and near) electrical circuits, including on the surface of wires, and in the wider electromagnetic field in the space around the wires.

It’s a follow up video to the controversial video that was dicussed on this thread:

Understanding this helps me to appreciate why the measurements we have do not always encompass everything about sound quality in audio systems; how noise works in hifi systems; and how materials and design choices change the sound signature of systems in complex and sometimes unpredictable ways.


I’m not going to spend 24 minutes watching, but noting your comment regarding ‘skin effect’ with electricity travelling on the surface of conductors, does he identify the sort of frequency at which the skin effect might start to become of significance in the range of sizes of conductor in use in hifi?

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No the video is not about hi-fi at all.

Can he also explain Quantum Mechanics?

I don’t know.

I don’t watch his videos very often, in fact hardly ever.

You are making judgements there without knowing anything about what I know already of electricity and electromagnetic propagation. The one and only thing my does tell you is that I don’t wish to spend 24 minutes of my precious time watching a particular YouTube video.

Personally, I have a strong dislike of YouTube “tutorials” because, based on ones I have seen, they are often poorly done, or miss out important and balancing information. And certainly in the case of some of that I have seen, I can find out more spending the same amount of time reading.

You are quite right in this statement. But you still seem to be implying that by not choosing to spend 24 minutes of my time watching that video I am denying myself the opportunity to learn. As I said you have no idea as to what I know already about a subject in which I have been intensely interested and dabbled in various aspects of since the age of about seven, over 60 years ago. I continue reading and learning new things about this, and many other subjects to this day and have no intention of stopping.

Yes, it is possible that the person presenting this video has included something that is new to me. And indeed without watching it I will not know if that is the case. Is that any loss to me? Of course I don’t know. Is 24 minutes watching a video a loss to me? Well if it only covers things that I know already then it most definitely is. A fundamental problem with videos (generally, because they may be exceptions) is that they tend not to have a list of contents indexed to allow rapid finding, that would allow the watcher to find out in advance what things are being presented or discussed, and allow focusing on particular things without wading through the whole lot.

If you want to be agreeable, please don’t make sweeping suppositions or implications about why someone might choose not to spend their time watching particular video.

If I am tempted to watch a particular video I will watch the video until it becomes clear that it’s not useful or interesting, and then stop.

One would not have to commit to the whole 24 minutes, perhaps just 2 or 3 to make such a decision.

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That may be the case, though it would be unlikely tell me if there’s something in it somewhere that is is new to me. But I am predisposed against the whole utube video thing having seen too many that are from rubbish to just time wasting, and, worse, too many with people who purport to be experts but actually aren’t. The problem is that because there is a lot of money to be made out of utube it encourages all too much video diarrhoeia. That is not saying this one is in such category, but is why I prefer not to expend time looking.

Yes, the vast majority of YouTube videos are rubbish.

But there is some extremely good material on there as well.

The trick is to find a way to locate the excellent stuff that you seek, e.g. Tim Maudlin videos re. Philosophy of physics.

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I’m happy to save you 24 minutes here, @Innocent_Bystander (being aware of how long it must have taken you to write all those responses above), and tell you that he’s still only dealing with a DC circuit only and the skin effect (in the sense I think you’re using the phrase) is not dealt with.

It’s a nice demonstration not only of the effect in the original video but of dealing with objections that have been raised about certain details in it.

As I said earlier, Poynting vectors show just how trippy and weird even a simple DC circuit can be. The whole concept (demonstrated in a marvellously visual way in the video) still makes my head hurt a little, and to think that Poynting derived the idea over a decade before we knew electrons even existed is even more striking.



Yes, the presenter just mentioned once en passant and very briefly the fact that current runs along the skin or surface of a cable, iirc.

The video is not focused on the skin effect.

It’s about electricity and the EM field.

Not really - it was the charge distribution on the surface of the wire and its contribution to the E field which causes the current in the body of the wire that was being modelled.

Current flowing preferentially on the surface of a conductor is an AC phenomenon - in DC circuits, the current is distributed evenly along the wire’s cross-section.

I didn’t try to suggest that current only runs along the surface of a wire - just that, iirc, the presenter mentioned very briefly once that ‘current runs along the skin or surface of a cable’ - which does not preclude it also running through the body of a (solid core or twisted) cable.

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I watched the full video this morning. It was a good follow up on the original.


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