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

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Published 2023-12-06
In this video, I measure a wave of electricity traveling down a wire, and answer the question - how does electricity know where to go? How does "electricity" "decide" where electrons should be moving in wires, and how long does that process take? Spoiler alert - very fast!

I've been very excited about this project for a while - it was a lot of work to figure out a reliable way to make these measurements, but I've learned SO much by actually watching waves travel down wires, and I hope you do too!

There will be a Q&A about this video posted in a few weeks on the second channel, and if you head over there right now, you'll see two direct follow ups to this video with experimental details, and a section about "impedance matching" that was cut from this script.
youtube.com/@AlphaPhoenix2

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Media Credits:
Slomoguys clip used with permission. Thanks Gav!    • Elephant Rifle Annihilates Ballistic ...  
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0:00 a hypothetical question
3:30 Measurement difficulties
7:44 Individual oscilloscope traces
10:23 Electricity moves through Y circuit
12:54 The single wire experiment – how electrons move
17:32 Electrons hitting a dead end
20:23 Revisiting the Y circuit
22:16 The water channel model

All Comments (21)
  • Corrections and FAQ in this comment! Check out the other channel for follow up videos, and video Q&A that I'll be posting in a few weeks with questions from here and from Patreon! youtube.com/@AlphaPhoenix2 Check out the Patron page if you want to support the channel, get early access to videos, and join us on Discord! www.patreon.com/AlphaPhoenix Thanks to @ElectroBOOM for giving me a sanity check on this data a few months ago! (I hope you like the final video) FAQ: 0) Questions about the experimental setup (including the effect of the probes on the circuit while I was measuring) are here! https://www.youtube.com/watch?v=sty0Y1qmgEYc If anybody wants to recreate this project, or turn it into an undergrad physics lab. hopefully there's plenty of info there! If I can remember how to use github I'll post some of my visualization code and leave a link on that video. 1) Lots of commenters have that I'm confusing voltage and current at times, but I tried to be very careful with my language. Current is the actual motion of the electrons, and in the graphic I showed with the blue dots moving around, I'm calculating that motion based on the voltage. it's basically the current that is NECESSARY to produce those voltage patterns. I also did a measurement where I measured the current directly by placing a very small resistor at the input lines and measuring the voltage drop across it over time, so I know my calculation lines up vaguely with that, but it WAS only a measurement at one point. If somebody wants to put a quarter ohm resistor every 4 feet along a wire and measure more voltages, I'd LOVE to see the data! I'll talk about the script a bit more in the Q&A video that hopefully will be out in a few weeks! 2) When you first flip the switch, the battery doesn't actually see a "dead short". The current out of the battery initially is limited by the line impedance, which depends on the properties and dimensions of the cable. In this case, it's the same current you'd get by bridging the switch with a 150 ohm resistor! 3) A lot of people have questioned the use of the words "communicate" and "sending information". I admit I anthropomorphize a bit too much in this video, but particles and groups of particles "communicating" and the rate at which "information" can move are very important hard physics terms that don't imply the particles are thinking. "Information" here consists of things like partical position, and they pass this information between each other using the electric field. 4) Water is a compressible fluid. if water wasn't a compressible fluid than pressure wouldn't work and water wouldn't be able to flow around corners in pipes. The way I'm using it it's actually EXTREMELY compressible (in the lateral) direction because it's allowed to expand upwards without getting significantly denser. Electrons in a wire are orders of magnitude less compressible than water, but it's still worthwhile to think of them bunching up! 5) ...........keep the comments coming! i spent like 4 hours reading comments yesterday lol
  • @jbf81tb
    I have a PhD in physics. That graph is easily the most instructive, intuitive thing I've ever seen about electricity and it's relationship to the wave properties of the electric field. Absolutely incredible experimental design and presentation.
  • @3blue1brown
    Excellent video, those data-driven animations are extremely clarifying. I'd never seen someone show a circuit settle into a steady state like this, thanks for putting in the effort.
  • @1776FREE2
    “In this video we’re actually going to be able to record this circuit fast enough to differentiate between these four options.” What a Time to be alive!
  • Well this is ridiculously cool. This makes electricity make so much more sense, and what an amazing visual!!!
  • @cameronbehar7358
    That bar graph animation was one of the single best scientific visualizations I’ve ever seen, all the more compelling because it’s empirical, not simply modeled. Fantastic.
  • @Tsardoz
    I am PhD Biomedical Engineer (hons electronic) and also MD (medical doctor). Congrats on excellent video. The same thing (wave reflection) happens in your body every time your heart beats. The outgoing wave in the large arteries reflects off the capillary bed and you get amplification of the pressure (equivalent to voltage) on the leading edge of the (systolic) pressure pulse. Not only that but as you age the blood vessels get stiffer (lower capacitance) and the distal impedance increases, further increasing systolic pressure. Of course you also get a multitude of reflections at every branch. Congratulations, if you understood what I just said you understand more about this than almost all doctors. PS. I have the exact same oscilloscope next to my monitor right now!
  • @pointlinesquare
    When you said "and then I spent hours stripping wire at hundreds of locations to attach the probe clips" I rolled my eyes and thought whyy?!. But your determination to follow through is what makes this so special! Brilliant combination of experimentation, video, narration, and the data-driven animations... really impressive.
  • @jakobmoderl3331
    Fun fact to this video: Since the waves reflect once there is a change in the wire, e.g. an "unexpected" open end because the cable was damaged somewhere, the time between connecting the battery and the the arrival of the reflected wave can be used to measure how far away the fault in the wire is (its called reflectrometry). This is extremly useful when diagnosing where cables buried in the earth are damage so that you can dig up exactly the damaged section instead of having to dig up kilometers of wires until you find the faulty section.
  • @theslowmoguys
    Absolutely amazing “footage.” Who needs expensive cameras when you can get such good data from an oscilloscope. 🤯
  • After teaching basic electricity for 35 years or more this is the best explanation and visualization that I have seen regarding current and current flow and how the wire bunches up its electrons and releases them quickly or slowly and remember 6.25 million million million electrons flowing through a wire in one second equals 1 A so electricity is it all that magic you can actually see it and measure it
  • @daniellewis3330
    Wow. I have a Ph.D. in Electrical Engineering, and I am impressed at how clear and effective this video is. Excellently done!
  • @XIIchiron78
    I've seen the "ringing"/"bouncing" oscillation effect on an oscilloscope when connecting wires before but to see it graphed out spatially like that is incredible
  • @taylankammer
    IMO this is hands-down one of the best physics channels on YouTube. Your ability to turn highly abstract and complex concepts (like the "speed of movement" which is a video I'll never forget because it blew my mind) into real-life experiments using actual measuring equipment is just amazing.
  • @samuraiguy0000
    I've been utilizing "electricity moves like water" as a basis for troubleshooting and planning for decades, this is be best description, example and proof of this thought process I have ever experienced. Well done. Subscribed.
  • I remember doing this exact experiment in Physics class in 1977 when I was in 11th grade. We compared and contrasted water waves with electric current over time and determined the speed of the electrons as shown on a primitive oscilloscope (about five times the size of a modern one). I am glad to see that there are those that are regaining the knowledge nowadays.
  • Your vids have already changed my understanding of electronic fundamentals, but this visualisation in particular absolutely took it to the next level. Thanks.
  • @daalfredLP
    As an RF Engineer, the stuff you're talking about is my daily bread an butter. Still, I've never seen such a good visualization of electromagnetic waves, let alone based on actual measurement. Really cool and educating, even for professionals!
  • @darrcook1
    It's so awesome how you genuinely dig all of this -- you could have talked about it for hours! People with your enthusiasm make the best teachers! THANKS!