Watch electricity hit a fork in the road at half a billion frames per second

I want to hijack this comment to plug AlphaPhoenix ( link ), who is responsible for by far the best explanations of electricity that I've encountered in any format. For instance, this one that clarifies what happens when you try to send electricity on an open circuit, and (IIRC this is the right one) what impedance mismatch is actually about: ▶ this video

Excellent post! Controlled impedance took me a long time to wrap my head around when starting PCB design, the moment when it finally clicked was watching this excellent AlphaPhoenix video ▶ this video asking and practically demonstrating the simple question: When you flip on a switch, to turn on anything, send data, morse something etc, how does the circuit know how much current the load at the other end needs? Spoiler: Given that information can't travel faster than light, the simple answer is: it doesn't. So it just guesses and adjusts, which you don't want as it gives you exactly the ringing etc Heaviside identified. The video is a nice complement, as it perfectly visualizes the issues at play. It's a pretty wild bit of understanding to have, even in simple situations like flipping on a light switch.

This spurred on some other videos from another youtuber that goes by AlphaPhoenix, he went way into all the details on it including measuring the complete flow of the wave of the electrical power and how it all works. link ▶ this video link (on his second channel, has a lot of "behind the scenes" of how it was done) It goes into a lot of depth of how the wave propagates, including measuring it at effectively "a billion fps" (he goes over how he does this) along the wire and how impedance matching works, etc. It's about 2.5 hours of video IIRC but it's probably the most detailed and easy to understand demonstration and explanation of all of it that I've ever seen.

As a matter of fact, yes! This YouTube video is probably one of the most amazing things I have ever seen, he measured the change in voltage traveling along a Y circuit, where one end is open and one is closed. You can see the voltage “ripple” through both branches of the circuit, reflect of the ends of the branches, and eventually settle into steady state. There are limits to this way of thinking (for example, water can’t travel in the space between “tubes”, but electricity can), but it is a very good way to approximate it. ▶ this video

Well, the water analogy actually holds up quite well if you consider the charge field moving, not the electrons themselves. This guy has a lot of great videos using water channels to explain electricity. It is fascinating how under a high speed scope, you can see the electrical Charge “flow” like water down each branch of a circuit. ▶ this video

AlphaPhoenix's measurements, experiments and visualisations really help! They show some things that are normally not even taught and even electrical engineers will appreciate to see this. This video he made about it is very good, and worth watching if you wonder about how electricity propagates from one end of a conductor to the other. ▶ this video

Turns out "water in a pipe" is actually surprisingly accurate, just that the "waves" are sloshing around at half the speed of light. ▶ this video

well, the truth turned out to be quite complicated; see also link and ▶ this video . the result is more complicated than just a single time delay, and the details of the experimental setup (like the wire diameter! and load impedance relative to transmission-line pulse impedance) matter a lot. in alphaphoenix's first experiment, putting 5 volts into a kilometer of wire, he got 0.2 volts across his resistor immediately, then after about 1.6μs, a jump up to about 2 volts, and then a gradual rise to 1.7 volts, some overshoot peaking after another 1.6μs, and then settling back down to the 1.7-volt level (derek's results in the linked video, which incidentally links to one of the two i linked above, were quantitatively different but qualitatively similar) the really unintuitive thing about this i think is that people think of electrical energy as flowing inside wires, when actually almost all of it flows around the wires, as veritasium explained quite ably. this is something people doing high-speed pcb layout have to deal with a lot in order to avoid emi problems as i understand it, derek has a ph.d. in physics, or actually in physics education research link . that doesn't mean he knows everything about physics, but generally my experience with people in ph.d. programs is that they're good at listening to counterarguments and admitting when they're wrong, and also seeking out experts before publishing (i think the veritasium video does contain a minor error in that it says electrons

The neat part is that it's almost instantaneous, but not quite. How electricity flows through analog circuits and chooses the right path is another fascinating subject. Seeing how it actually works "in action" seems to glimpse some insights into ultra-fast computing paradigms: not just computing with analog circuits, but also structuring computation like circuits. ▶ this video