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

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.

Special thanks to my top Patreon supporters!
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Jeffrey Mckishen

Media Credits:

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

[AlphaPhoenixChannel]

Corrections and FAQ in this comment!
Thanks to @ElectroBOOM for giving me a sanity check on this data a few months ago! (I hope you like the final video)
FAQ:


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) the comments coming! i spent like 4 hours reading comments yesterday lol

[bluebrown]

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.

[cameronbehar]

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.

[ElectroBOOM]

I love how you actually showed the waves! TO knowing is something, to seeing is something else!

[jakobmoderl]

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.

[thethoughtemporium]

Well this is ridiculously cool. This makes electricity make so much more sense, and what an amazing visual!!!

[theslowmoguys]

Absolutely amazing “footage.” Who needs expensive cameras when you can get such good data from an oscilloscope. 🤯

[Point]

Retired in 2013, teacher in HS and college adjunct with MS in Physics. Love the graph with the animated bar graph and point electrons below! These tools weren’t available when I was still teaching, but this is something I for sure would have had the kids watch! When I first saw it run, I totally geeked out on the reflected wave. Just like a compression wave in a spring hitting a barrier, or light ray entering a different refractive index… I started thinking about wave-particle duality of the e-. I’m so glad you went to it in the second half of the vid! Thanks for the mental stimulation, love your work!

[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.

[allonewordinlowercase]

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!

[mikelyons]

This is the kind of video that defines the need for YouTube. This is awesome. Thank you for doing this!!

[joemusicman]

I have a bachelors in Electrical Engineering and have worked in the profession for 34 years (retired). I have never seen electricity explained this intuitively in college or at my job. This was awesome. The similarities between fluid and electricity behavior are so useful to help understand electricity. It's a very tough thing to grasp due to how fast things happen on an atomic level. You figured out a creative way to capture it.

[danreyn]

As a physics educator at a university, I love this video for so many reasons. First and foremost, this was amazing science done right. You presented a problem, made a set of competing predictions, established what data you were going to collect and related your predictions to your data (you said what we expect to see in every different case), then you took a copious amount of data like a good physicist), you analyzed it well with lots of figures, and you discussed how it confirms only one set of predictions, discounting other theories. Great science, dude, A+. The second reason I like this is that it doesn't hype up the science artificially. You let the science make itself awesome, unlike certain other YouTube creator (looking at you, Veritasium). And third, it reinforces my own sense of "yes, I know what stuff does because I'm a physicist". When you asked the question I was like "obviously C, because it shouldn't be able to do the other options". Nice to see I know my stuff. Honestly, I wish I could teach my students to understand the scientific method as well as you seem to. If you were in my lab course, I'd give you the A+ and tell you not to come back. "Student has demonstrated all skills that we are trying to teach in this course. Credit granted with 0 revisions"

[Ilmari_Hirvonen]

I’m an electrical engineering student. I remember learning this in circuit analysis but this visualization is so much better than the things we had.

[makespace]

I read down quite a number of comments looking for the key words, in engineering speak. Not finding them I decided to write this comment.

You did an excellent job of revealing a phenomena that has been understood since the time of copper wires for telephone circuits. Your wires constitute what is called a transmission line: The wires have a finite total resistance, and some amount of capacitance over the length of the twisted wire path. It is that resistance and capacitance that are responsible for the waves and reflections you measured. What you did was create an instrument called a Time Domain Reflectometer! With just a bit more math you could have determined the lengths of each section of wire, and where the Y-point was, just from the graph on the oscilloscope. Kudos on your achievement!

[Longnose]

Holy cow! I have a masters degree in physics and this is one of the most intuitive and understandable explanation of electron flow I've ever come across. I'm amazed on how much information you could gain with this "basic" setup. I also love your systematic approach and the brakdown of the system. Very well done sir!

[XIIchiron]

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

[abhijithcpreej]

This channel is like a saving grace to people who already know the math and feel the physics but don't quite get it. It feels so good to understand what you thought you knew.

[clptp]

As an RF engineer, this is actually quite intuitive. When you flip the switch, the current rises rapidly, which can be seen as high-frequency signals (just look at a Fourier transform of a rectangular signal). These high-frequency AC signals travel as waves through the wire, which is why the voltage appears like a traveling wave. It would be very nice to repeated that experiment with purley high frequency AC signal source. Howevere the Equipent to do so is very expensive. Maybe Rohde & Schwaz or Keysight might be interessted in sponsoring something if you ask.