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

Quick Editor's Note: The video you're about to

watch

is based on information from these three videos, one where I reduce

electricity

and show that it is related to the speed of light, a

second

where I show that

electricity

prefers to flow through of connected wires and unconnected wires to solve the Maze and a third where I try to provide an intuition for voltage, current and resistance using many different analogies, in particular a narrow channel of water. You don't need to have seen these videos to see this one. but if you want to learn more, thank you it exists here.

I have a very uninteresting circuit, but it will become much more interesting when recorded at a ridiculously high speed. We have a battery here, this is just a regular 9 volt battery, although this one is almost dead and although it's not plugged in yet, this is our power source. Here on the left we see that the cable splits in two. The electricity from the battery could take this branch where it would meet the disconnected wires or it could take this branch where I soldered. the wires together Core level electrical engineering tells us that of course the electric current will flow through the connected wires and not through the disconnected wires, which means that we will actually have a loop of electrons in motion.

Move away from the battery on the black wire by turning the corner at this solder joint and then move towards the battery everywhere on the red wire here where the wires are disconnected there are still electrons in the wire but none of them should move because they don't can go nowhere, the question I want to ask is how do you know that if I connect this battery here, suddenly the electrons will start to make their way through this wire, but we know from Ohm's law that the voltage of the battery and the wire resistance should cause a very specific amount of electrons to flow through this circuit every

second

.

By the time I connect this battery, the other end of the circuit is a meter away, information traveling at the speed of light requires more than 3 n seconds to go through this configuration, which means that when I connect this battery and the battery asks the universe: do you know how many electrons I should pump into the black wire every second? It takes more than six NCS to get an Answer so what do you think is going to happen based on the comments I've received on other videos? Here are four possible answers. Option A. The electric field has already solved the circuit.

As soon as the battery is connected, the correct amount of current will flow. through the connected branch and no current will flow through the disconnected branch option b the electric field has already solved the circuit but it still has to update the information at the speed of light, so as soon as you connect the battery, the correct current begins to flow the wires in a kind of bubble that expands from the connection point option C, the battery pumps an arbitrary amount of current into the wire and, even though one branch is disconnected, the flowing current is divided when it reaches the

fork

and goes down both cables, although this is initially incorrect, it eventually stabilizes option D initially nothing happens, the battery updates the electric field at the speed of light and once the information has returned from the other end of the circuit, the correct amount of current begins to flow in the connected leg at once.

In this video we are going to be able to record a circuit like this quickly enough to differentiate between these four options, so think about it for a minute, guess and leave it in the comments while the title card plays. Are you thinking about it? I'll come back to this in more detail at the end of the video, but I wanted to give you something else to think about now. This is the branched circuit replicated using my favorite water channel model for electricity. Do you think electrons? on the cable will do the same as the water in this model even though flipping a switch is a much more dynamic system than the one the water model had to handle.

You can refresh your guests one more time before I show them the real circuit in motion Unfortunately,

watch

ing electrons moving through wires is obscenely difficult and I think this is one of the reasons why it is so difficult to learn about electricity. I didn't properly understand the concept of line impedance, for example, until I built the apparatus I planned to use for this video and used it to observe waves of electricity traveling through wires. A normal camera like the one on your phone can't see the electron m and even if it could, the changes occur on the order of the speed of light.

For reference, this is a recent video of the guys in slow motion taken at 82,000

frames

per second which sounds very fast, but between each frame of this video, light can travel more than 2 miles (3.5 km) from electricity As the signals and energy delivered by electric current travel anywhere between the speed of light and perhaps

half

the speed of light, we clearly cannot use a normal high-speed camera to observe changes in a table circuit model that is only a few meters long, in fact, we are going to need to cheat even more with slower electricity and longer cables.

Sorry for the really weird camera angle for these shots, but this literally takes up the entire room and I can only set it up on the floor unless I set it up outside, so this is what we have. I tried a bunch of methods to create extra slow transmission lines but ended up with this homemade twisted pair where electricity travels at about 60% the speed of light, but since that's still too fast I made a lot of this twisted pair and ended up zigzagging over these wooden

frames

. Each of which contains approximately 23M of cable. I'll get to some of those decisions later, like why I have this twisted pair and why my scope probes are visible. this, but for now we have a larger, slower version of the circuit from the intro at the top here, at the beginning of the circuit, we literally just have a 9 volt battery and that 9 volt battery connects to this circuit, which it's an electronic switch that is Basically, I can just plug in the battery faster than I could after that, it goes into this wire, this twisted pair that goes zigzag, zigzag, zigzag for 23M in this Y where we have three wires connected and then zigzag, zigzag, this way. to an open circuit where the two wires are disconnected and it goes zigzag zigzag zigzag to here where the wires are connected, which means after we plug in this battery we should have electric current flowing through these wires and electric current flowing through these wires where They are shorted, but we shouldn't have electricity flowing through here where the wires are disconnected, these are basically connected but they don't really do anything now, the round trip time at the speed of electricity is about 500 NCS when I connect this. battery or when this circuit connects to this battery very, very fast, it takes about 500 for that information to get to both ends of the wire and back, that's slow enough for us to measure it, the most common tool.

To analyze very rapid changes in electronic circuits it is called an oscilloscope. I have one here, we'll use it in a minute, but in general I find oscilloscopes and circuit analysis with oscilloscopes to be very, very limiting. An oscilloscope is basically a voltmeter. combined with a really accurate clock and it will show you a graph of how the voltage in a wire changes over time, for example what if you wanted to know exactly how fast this switch is when the battery is connected, how fast it turns on the voltage? the cable goes from zero to maximum, so in this graph the x axis is time and the Y AIS is voltage, so when we connect the battery we can see that the voltage goes from zero to high in a period of time very short. the whole event takes less than 10 no and this is a very quick change in this particular case it gets a little bit stranger CU When we zoom out we can see that there is a small step here and then there is another step here and I mean This is a little strange, like there was a drop right there before it stabilized, like what's really happening.

If you want to play this as an animation, we can imagine flipping this switch at an absurdly fast speed, the voltage at this point in the circuit increases. goes up and then mysterious things happen in the rest of the circuit and then the voltage here goes down a little bit and then more mysterious things happen in the rest of the circuit and then the voltage goes down and ends up stabilizing, that's why I find The oscilloscope traces are so limiting that you can see what's going on in one place, but you can't really see everything. The trick we can use is to probe more points on the circuit at once if I take an extra set of oscilloscope probes and connect them.

In the middle we now see something very interesting, the voltage at this point in the circuit does not increase until 116 NS later, if I measure the voltage at this point at the end where the wires are connected, we basically see, oh man, it's very loud. Melt my fingers together, that will help if I measure the voltage at the end of the circuit that was shorted where the wires are simply soldered. We can see from the scope that the voltage basically stays flat all the time, but now it requires it to. completely under the table, if we measure the voltage here, if we wait about 240 n seconds, we will see that the voltage at this point to the end of The Wire starts to rise, so let's run the same visualization again when we flip this over. switch we see the voltage on the switch increases and then something probably happens on the first panel and then we see the voltage increase in the middle and then something probably happens on both panels and then we see something happens on the panel with the wires disconnected, which was the panel where we didn't expect to see anything happen, then we start seeing voltages changing throughout the circuit, it's not very clear what is going on, this is why I sometimes get frustrated with oscilloscopes as a learning tool, because sometimes you can't see the spread, so with a couple of extremely tedious hours of stripping wires with an It looks like this if I show it in a more graphical view here maybe some of these features will become clearer.

I really love this footage and it shows that no, the battery has no idea how much current should flow when you plug it in, the battery is connected. a lot of current flowing slows down the wire when it gets to the Y, the current splits but also some seems to reflect back to the battery, that's a bit strange and now we have a pulse, actually two identical pulses traveling down both far wires, remember . this wire has the ends disconnected and this wire has the end soldered when the two identical pulses reach the end of their respective wires, the one with a disconnected circuit crashes into a wall, all that current builds up and the other shorts out . drops to zero and also sends that information back to the battery.

If I accelerate here we see some reflections, the battery realizes that it tried to send too much power the first time and slowly the whole circuit stabilizes, the actual flow of the electrons ends up following this slope as the high voltage in the battery drops to nothing in the wire short and disconnected where nothing should be happening, there is no slope, no voltage to make the electrons move until the wave actually reaches the ends of the wire looks identical because these current waves do not They know what is at the end of their respective branches of the circuit.

Once they realize what is at the end of their circuit, they transmit that information to the battery. This branch says, "Wow, I need." a little less current this way it looks like a wall and this one says hey I need more current make this hill a little steeper when both signals meet and eventually go back to the battery there is a negotiation and it requires a lot of back and forth communication In this case, the entire circuit took about 4000 NS to stabilize, i.e. eight round trips. I also want to point out that these cables cannot communicate with each other through this gap.

I just wanted to make it easy to compare the Waves by putting them side by side, so for those of you keeping score at home, the answer is C. Electricity takes a lot more than a round trip for the current to flow. stabilizes and the circuit obeys M's law in DC, but that leaves us with a few more questions, like what are these waves traveling through this circuit and how does the battery and switch assembly here decide how much current should initially flow in The Wire if you're just guessing and don't know how much current should flow to either end to answer those questions, I have a similar but simpler circuit set up here instead of a big branched circuit with tons of wires.

This is onlya direct path, so I have the same very fast electronic switch that connects the battery to the cable. and then I have 23M of my custom twisted pair and at the end two wires hanging free so I can connect any resistor I want as a load at the end of this circuit, which basically means we have a power supply and If you have a separate load by hundreds of seconds of delay time, it's very easy to come in here and say: I know the resistance of the wire. I know the resistance of the load.

I know the built in resistance in the power supply and you can calculate it. how much current, literally how many electrons per second will make their way through this wire, but as we just saw, the right amount of electrons don't flow the first time you press the switch, they have to bounce around and calculate. For the first test, I'm just going to cut the end off. I soldered these two wires together so that this big long string ends in a zero ohm resistor. I spent what ended up being quite a bit of time writing a script that brings in these voltage traces and produces an exaggerated view of how the electrons actually move in The Wire, so I want to make it very clear that this graph above is real data that I actually collected. , are 20 individual osiloscope traces playing at the same time. time and this is a very exaggerated animation of the movement of the electrons based on that data and then this final graph is a realistic although extremely noisy graph of the drift velocity of the electrons along the length of the wires which we will talk about in a minute, but that's also based on the raw data for now let's cover most of this down to the fundamental point here is the speed of electricity and the speed of electrons and those are not the same thing if we look at this way of traveling From the cable we see that it travels this way 23 m in approximately 120 NCS, which means that it travels at almost 200,000 km/second, which is like 2/3 of the speed of light, which is absurdly fast;

However, if we look at these electrons that have started moving, they are going much slower on the graph. the individual electrons move about 10 times slower than the wave and that's an exaggeration because in reality the electrons in this wire travel about 10 trillion times slower than the wave, but that doesn't make a very understandable graph, but they were drawn accurately, you would never be able to see that they were wrinkled in some places and more spread out in other places because the spacing just doesn't change much, what it says is the squishing and scattering of electrons in different parts of wires that make the Electrons do what they do and flow through the wires.

If we look at the wires, these are the two twisted pair wires, although the twist doesn't really matter when we flip the switch and this wave travels down the wire. We see that electrons are pulled from one wire and pushed to the other, but in the end the electrons have not started moving yet. Any given point on this trace at the top is the voltage or potential difference between the twisted pair wires below. when this voltage goes up here but remains zero here, we are saying that in this region there are more electrons in the wire than in this wire, but at the other end there are the same number of electrons in both wires, of course this is about of changes as this wave reaches the end of The Wire, all these electrons start moving, so in answer to our first question, what are these waves?

These waves are waves of motion and waves of electrons that clump together and contract in an instant if there are electrons moving to the right. on this part of the cable and without moving on this other part of the cable, the only way that can happen is if the R elects between those two regions on this part of the cable are getting closer and if we play this footage. Go ahead, that's exactly what we see. It's a common argument in my comments section that these waves of electricity are just the electric field and that the electrons don't really move, but if that were the case this zigzag design wouldn't work, the electric field would. cover the entire panel faster than you could measure it, these phenomena only make sense if the electrons actually slide down the wire and clump together, even slightly, that's why electricity follows the wires and cables, it can only go where electrons can slide.

Moving on, I originally had this circuit set up where the wires at the end were shorted, so it was basically like a zero ohm resistor, but now I cut them so there's an Infinity Ohm resistor right here where the two wires are, you know . hanging freely, so what do you think is going to happen in this case? There is no way for the electrons to flow down the black wire all the way to the end, somehow magically jump this gap and flow back along the red wire, but we know that when we flip this switch, we will have current electrons that will start moving in this part of the cable by the time we flip this switch, so what will it look like when it gets to the end?

It will look like this after we flip the switch we get exactly the same step, the same wave of electricity at about 2 and 4 volts of potential and about 15 milliamps of current flows in that part of the wire, but when that wave reaches the end it doesn't can go nowhere. Basically, these electrons hit the end of the wire and build up. Now we have a large steep voltage slope in the other direction. If the first slope accelerated the electrons towards the charge, this reverse slope decelerates the electrons and surprisingly the magnitudes match for all the electrons. starts moving, then the reflected wave can cancel them perfectly and they all stop moving, of course it bounces back and forth a little more, but after all we end up with two wires full of motionless electrons, the fact that at the end of this animation This extremely data driven animation where all the electrons stop moving makes me very happy.

The fact that the wave going in one direction is perfectly canceled by the wave going in the other direction when it reaches the end is cool and can be measured with sufficient precision. making an animation like this with an oscilloscope that costs only a few hundred dollars. I was very excited when I first saw this animation, but both wires have different potentials, there is a voltage difference between them, if you want to get technical, we. Now we are physically looking at the capacitance of the wire measured in charge per volt, how many charged electrons we need to add to a wire to change its voltage.

This also indirectly answers our second question: in both cases, the exact same wave came out of the battery because the circuit at this end did not yet know what was at this end and the magnitude of this wave was largely controlled by the cable capacitance. How many electrons can be packed into this wire when a certain voltage is applied? Or to be linguistic about it. The ability of the wire to hold extra electrons, this value is very high for cases like this where there are nearby wires wrapped in insulation and extremely low for wires that are far apart with nothing in between, so now let's go back to the circuit in the form of And and, hopefully, you'll see all of these effects present in a much more complicated model, so now we understand this first bit, when we send a voltage pulse down the wire at the ends of the branches, the electrons are still not moving, but this wave has been everywhere. the electrons have started moving and at the edge of the wave the electrons are bunching up or spreading out now when this pulse reaches the branch three things happen part of the wave is reflected back part of the wave continues towards the connected branch and part of the wave continues on the disconnected branch, these waves continue until they hit their respective loads, a zero ohm resistance or an open circuit or an infinite ohm resistance, just like in the single wire test, we see that the electrons that hit the open circuit accumulate and reflect. backwards it stops all movement and on the other branch the wave is reflected downwards further accelerating the electrons in the wire.

This branch circuit is a dramatically more complicated system than the single wire terminated in a resistor, but hopefully you can see the same patterns in both. We can continue to track reflections, waves and individual interactions between electrons in all these wires and carefully predict what will happen next or we can just skip ahead to the end and see that all of this barely matters because after a few hundred NCS everything becomes clear and we get exactly what we expect: a downward gradient from the power source to the load where the DC version of the MMS law holds for all locations.

This is the same net result I measured in the electric maze video, but at that scale I couldn't record it fast enough to show you how it got that way. Hopefully it makes a little more sense now and you can imagine these waves filtering through all the possible ways to solve that maze in one go before the circuit settled on that outcome at the beginning. I mentioned that the Water Channel model was coming back and I want to show you what parts of the Water Channel model are applicable and where you have to be careful and then somewhere we have one, there are only three leaks, it's pretty good.

I recreated the circuit as best I could with acrylic sheet water channels and used large containers of water as supply and load so effectively that we have two grounded capacitors, a switch and an extra piece of wire, so check out these shots side by side in In both cases, the wave leaving the supply travels downward at the first leg, splits at the branch, rises at the dead end, and cuts downward at the open end. The fact that this water channel model can so accurately represent the dynamics of electricity in a completely different system and one that operates on time scales that are orders of magnitude faster than water is truly amazing to me. , but it's not perfect, strangely in the water version the reflections are not as pronounced when the signals hit the charges at the end.

I absolutely see one wave building up and the other falling, but overall the water dynamics are a little more direct and the signal going back to the power supply isn't as obvious. One reason for this may be that the parameters of the circuits do not match. If I repeat the electricity experiment with a higher resistance wire, not with impedance but with resistance, we get a slightly closer analogue where the reflections of electricity decrease significantly. , but while water in a narrow channel and electrons in a wire show a lot of similarities, seriously. I could go on listing them for 40 minutes.

Inertia is a really complicated thing. If you look at this model from above, you can see that it is not symmetrical or straight. The way water maintains inertia in corners is extremely different from the way electrons accumulate. an effective inertia while derived by creating a magnetic field around the wire, this slit for example would never appear in the flow of electrons in a wire and in the end I couldn't create a perfect low voltage supply to lower the signal, but this It's something that's really easy with cables. I always imagine circuits, even dynamic ones, with waves flowing through these channels, but sometimes the mental image with idealized water flowing through an idealized trough is a better analogy for electricity than building one in real life and filming it.

However, in real life, even this real model with all its imperfections is an excellent qualitative model that I think provides a lot of intuition for an otherwise very difficult topic. Of course, what really happens in my head is that when this doesn't match, I start thinking about a more complicated electronic circuit that would go better with this, like this milk jug at the end is basically a capacitor and the fact that I cut it out turns it into a voltage regulator and it's much better than basically what I had before. like a voltage sensitive resistor where I ended it anyway.

I hope you learned something about electricity from watching this video. I certainly learned a lot about electricity from making this video and had a lot of fun trying to figure out how to film electricity at ridiculous speed. and thinking about the equivalent water model, I feel that I am completely unable to write a short script. A lot of things were removed from this video, especially a more mathematical view of this circuit and how the strengths can be calculated. of these waves and much more with the single cable that was terminated with various resistors so that everything ended up becoming another video, you should head over to Alpha Phoenix 2 where I have the questions and answers from my previous Mainline video posted along with other short videos. which I think you will enjoy thanks for seeing us until next time