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

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.

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.

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