Does Electricity REALLY Flow? (Electrodynamics)

Does Electricity REALLY Flow? (Electrodynamics)


This episode was made possible by generous supporters on Patreon. Hey Crazies. Welcome to part three of our series on electrodynamics! In part two, I made the following comment: We usually have a bunch of charges moving together in something we call a current. Hmm, I think that deserves a little more attention. If you’ve been watching this channel for
a while, you know language is tricky business especially in science. You have to be careful with your word choices. The word “current” is usually used to
describe a fluid like water moving continuously in a certain direction. But does charge actually move like water? We certainly thought it did when we gave it that name. But to answer this question, we need to delve
a bit deeper than usual into materials. First, materials are made of atoms. A bunch of protons and neutrons surrounded
by a cloud of electrons. Those electrons are the lighter looser particles,
so they do the moving in materials. Second, we like to divide materials into two categories:
conductors and insulators. A conductor is a material that freely allows
the flow of charge. An insulator is a material that does not allow
the flow of charge. Either type of material can become charged. What matters is whether or not the charge
can move once it’s there. Category Alert! Category Alert! Category Alert! OK, OK! I’ll mention it! Stop! Quick disclaimer: always be cautious of categories. They give us little bite-sized pieces our
limited brains are capable of understanding, but reality consistently resists that kind of simplicity. Like most things, materials fall on a spectrum:
Conductors on one end and insulators on the other. No material is a perfect example of either type, but the three best conductors are silver,
copper, and gold, in that order. It’s no coincidence that those all fall
in the same chemical group. They each have one very loose electron on
their outer edges. That alone doesn’t make them a good conductor though. A material isn’t made of one atom. It’s made of a bunch of them. We need to see how those atoms work together. Atoms are always bonded by their electrons. In metals like copper, the electrons tend
to form one big cloud for the entire material. So this really comes down to the quantum states
of the electrons in the material. Specifically, the energy levels. In a single atom, electrons can be in a variety of
energy levels, but when atoms are together in materials,
those levels are separated into bands: A conduction band and a valence band. The lower energy levels don’t matter because they’re buried. What separates conductors from insulators
is how much energy it takes for an electron to jump from the valence band to the conduction band. For insulators like glass, the gap is really big. In semiconductors like silicon, the gap is small. In conductors like copper, there is no gap. Valence electrons are conduction electrons. That’s what makes them so conductive. There are already electrons in the conduction
band ready to go. If they get a reason to move through the material,
they’ll do it. But is that how water moves? Well, kind of. We want to be careful with our comparison here. The analog for charge is the water. Those are normal-scale things. The analog for a single electron is a water molecule. They’re microscopic things. We need to keep those two things separate. Let’s consider water first. Say we’ve got a long pipe with some water
at rest inside. The water molecules look like this, moving around randomly. If the water begins to move through the pipe
the molecules move too because they’re what make up the water. They still have the random motion, but they
now also have forward motion. A similar thing happens with the charge in
a copper wire. That wire is full of conducting electrons
just like the pipe was full water. Individual electrons are conducting around the copper randomly. If we connect a power source though, it’ll act like pump. The electrons will still have the random motion,
but also some forward motion. Except electrons are quantum particles, so
we don’t know where they are exactly. Grrr! You never let me get away with anything. Nope. OK, so according to quantum mechanics, if we know the energy of the electrons, we don’t really know their position. Those measurements are mutually exclusive. We don’t really know where individual electrons
are in this wire, but we do know the whole collection of them
is drifting forward. In fact, there’s something called drift
velocity that tells us how fast that drift is and it’s a lot slower than you might think. In this copper wire, it’s only about an
inch and half per hour. That’s 4 centimeters per hour. Wait a minute, then how come this flashlight turns on instantly? Because changes in the electric field transfer
at the speed of light. A flashlight is pretty simple: a couple batteries,
a light bulb, and switch. It could easily take an hour for the charge
to get from the battery to the light bulb. But, once the switch is flipped, the battery’s electric field travels across the circuit at the speed of light and all the charge in all the conductors moves at nearly the same time. How cool is that? Anyway, charge moves a lot slower in a wire
than water does through a pipe, but that’s OK. Electric current isn’t about speed. It’s measured as the amount of charge over time,
not distance over time. There’s a lot of charge in a wire, so a high current doesn’t actually need to move that fast. But does charge move through the entire volume of the wire? Sure. Well, at least when the current is direct. Alright, one more thing. There are two different ways charge can flow. Direct Current or DC, which is a steady flow in one direction, and Alternating Current or AC, which is a continuously changing flow that goes back and forth. Can’t you do either of those with water too? Well, yeah, but there’s something hiding
in the details. The inside edge of a pipe can put drag on the water, so it moves more freely near the center. For electric current in a wire, it’s the
other way around. The behavior of the atoms in the center restricts the number of electrons that can flow, so they actually move more freely near the edge. In DC, electrons flow through the entire volume in spite of this, but, for AC, the flow is mostly limited to the outer edges. It’s called the skin effect. What was the original question again? Does charge flow like water? Right. Uh, yeah, kind of. If you’re not concerned with where the moving charged particles actually are in the material, then water flow is a good analogy for electric current. So good in fact, it has a name: the hydraulic analogy. There’s a hydraulic equivalent for every circuit component you could imagine. It’s kind of fascinating. So, got any more questions about electric current? Please ask in the comments. Thanks for liking and sharing this video. A special thanks goes out to Patreon patrons like Kenny Holmes who help keep this show going with their generous support. Don’t forget to subscribe if you’d like to keep up with us. And until next time, remember, it’s OK to be a little crazy. By far, the most common comment from the magnet video was: What about Neodymium magnets? Neodymium is an element! Yes, it is, but the Neodymium magnets are not an element. They’re Neodymium-2 Iron-14 Boron. They’re actually a molecule, not an element. Anyway, thanks for watching!

100 thoughts on “Does Electricity REALLY Flow? (Electrodynamics)

  1. In all these models the electron flow is a back to back continuous flow of balls moving in the same direction, like soldiers marching steadily in lock step in a column. Everyone does their model this way. Since electrons are negatively charged and like charges REPEL each other it seems like the electrons in the model would fight each other instead of constantly marching in a steady direct line. Even in AC the soldiers are still marching in the SAME direction they just do a constant about-face. It seems the like-charged electrons should be in a game of ping pong or yo yo! Since we all have fine electricity and all our devices work there is some obvious concept I'm missing in all these models. It seems a line up of like charged particles in a wire wouldn't create any kind of flow at all but chaos, but I know that it does! I thought perhaps their distances would be far enough apart to overcome any force of repel, but the models seems to suggest it is quite crowded along the wire. Help!

  2. Electro magnetic conduction requires circular loops of wire in order to conduct an electric current from the magnetic flux.

  3. I think that this is the first time I've heard (or noticed) it phrased that the field itself moves… as in, it has momentun/velocity/direction?

  4. The electric field travels from the batteries at the speed of light… is that a simplification? I mean.. it would if a charge would appear from nowhere but all the charges are already there and the electric field exists thanks to them.

    However I thought that the effect is virtually instantaneous because the charges bounce with each other very fast creating a sort of wave witch propagates at relativistic speeds.

    But this doesn’t explain how the switch “tells” the battery to release the current. By the way is the current to wait for the switch or the switch who tells the battery to start?

    I can imagine the electric field lines and all that stuff but that just mathematics. How does it really work?!

  5. So in like a standard dc circuit, does charge move like sound, one electron bumps into another which bump into another and so on?

  6. You are telling that electrons are flowing . That means if we cut a wire the electrons should fall down only.

  7. Remember my question about voltage?
    I got a bit of idea in this.
    But, if the electric potential difference is more, I think then the drift speed should be higher.
    But according to what you say drift speed is constant.
    But then what is the role of voltage in the wire?
    I'm seriously getting crazy.
    But it's ok to be crazy right?

  8. 6:16 The "restriction" is not actually due to "the behavior of the atoms" but due to the changing magnetic field produced by the moving charges (the change is always resisting the change of charge motion). In the middle of the wire the magnetic field is stronger because there is more moving charge around. This effect is not very strong for direct current (the field stabilizes after a short while and then ceases the obstruction as it is no longer changing) but is very strong for alternating current with high frequency (the magnetic field changes all the time). There is a special type of wire called Lorentz wire designed to reduce this effect by bringing the charge from the middle near the skin and back.

  9. Correction – the propagation speed of transmission in a medium is less than
    the speed of light – there is a velocity factor to account for this:
    https://en.wikipedia.org/wiki/Velocity_factor

  10. 6:50 I love the Hydraulic Analogy! I'm a lonely electrical guy surrounded by mechanical guys. Whenever I try to explain electrical concepts, I just get blank stares until I start invoking hydraulic equivalents. Then the pinched pipes go off.

  11. What a crazy channel 😉 However, it surprisingly fits perfectly. Every joke has a meaning, is in context and helps in the understanding. Great work! Thank you very much!

  12. Electricity does not flow, it is pulled through the circuit. If it flowed you wouldn't be able to use it as and any power out would have an extreme amount amount of static build up

  13. 5:14 I wish people worked that same way in transit. As soon as the signal turn green, everyone floor the gas pedal, but no, they have to wait for the next car to start moving, it takes ages.

  14. hate to say it but wrong

    electricity moves like the energy moves through newtons' ladder balls – electrons do not 'flow' their orbits elongate, forcing neighboring electron orbits to elongate via 'attraction/repulsion', transferring energy, exactly the same as newtons' ladder balls
    (think of how a capacitor works, elongated electron orbits in the electrolyte)

    'bang' this end of a wire with a potential difference and it will 'transmit' through to the other end of the wire, ladder-ball-style

    Show less

    REPLY

  15. I have a question ……..An electron travels, atom to atom from one side of a battery to the other (Negative to positive). As it passes through a light bulb. Those electrons generate light, so what did the electron lose as for it to create the light.

  16. hmmmm the hydraulic analogy has me wondering what a primitive computer built solely from water plumbing and pumping would be like..

  17. reminds me of our college days when we first studied em theory and maxwell equations. it changed my perspective forever.

  18. Why is AC more efficient than DC? We all know the history of Tesla vs Edison but no documentary ever explains this most important part!

  19. Idk how anyone learned anything here. I cant recall shit three seconds later and didn’t make sense to me except complete the circuit

  20. @ The Science Asylum , magnetic field is created by two methods 1. by moving charges , 2. by changing electric field
    if in a conductor electron moving at speed of 4cm/hr then which method is used by motors to create magnetic field .
    and how a electric field turn on a incandescent light bulb ?

  21. i have 2 question in one concept please?
    do electrons ever finish in the conductor wire so no more current? Are we continuously supplied by electrons from source?
    do electrons go back to source or will they be drained into ground?

  22. The problem I have is that I do not understand why in AC charge flows at all. It just hops left and right without really moving in a particular direction at all..

  23. Assuming the battery is connected.

    If
    The speed of charge in wire is much slower than speed of water in pipe.

    Then
    So the speed of electricity is nothing but the change in electric field. Because the speed of electron (charge) is very tiny compared to known speed of electricity (What will be the physical interpretation of such a situation? Will it be like zig zag domino effect, because electron (charge) will have both random and forward motion… random because of nature of electron and atoms And forward because of electric field)

    Q. If the electrons are the charge carriers and the movement of charge (which are dependent on electrons for motion) is current electricity, then why do we say electricity is due to the flow of charges. Just change in electric field and potential difference can be said to be current electricity. Or both flow and field for current electricity and only field for static electricity.

    Q. Can Static Electricity be called Potential Electricity?

    Many Thanks for your quite intutive and conceptualy crystal clear explanations and demonstrations.

  24. So will you get more power from a flat foil wire, then from a big round wire of the same amount of copper? If electricity flows faster through the edges, then the center, a flat foil wire will be all edge.

  25. Hi thanks for this beautiful video. It would have been complete if you had also discussed the reason why we connect to a neutral or gnd to complete a circuit. Something we don't do with a water pipe

  26. Yep that electric wave is like a sound wave of electric field (so to speak). I heard of the skin effect but didn't know that's what it meant. One thing I wonder though. Electric fields do travel at the speed of light, but I've read that electricity only moves at about half the speed of light. Perhaps that has to do with the different permittivity.

  27. hey thanks, cool vid! what's the sound effect at ~5:13, where do you got it from, and can i use it too, please? greetings, and again thank you for taking your time to explain things!

  28. Hi. Can you please make a video explaining what makes a rechargeable battery charge other batteries faster? Thank you.

  29. I want to know, whether charge flows between two pointed electrode dipped inside a water tank, in an elliptical way

  30. Not a single human on this earth ever factually proved existence of imaginary elections. If electrons would actually flow, copper wires of generators in the power plants would be depleting and braking very often. Only magnetic field is propagating on the surface of conductors like waves on the surface of the lake.

  31. In the hydraulic analogy it says a battery is to a fluid pump. It should be a generator is to a fluid pump and a battery is to a pressure tank.

  32. In a power station generating electricity, there is a flow of electrons out of the station and into the cities etc where it is used. As there is a flow of electrons out of the station and electrons have mass, does the generator lose mass over time?

  33. Question is : Current (amps) in the NEUTRAL (not open neutral)back toward the transformer. does it reverse polarity, plus and minus the same as the hot side. Or does it only go in one direction. And lastly, how is it (current) able to
    flow in the neutral if the VOLTAGE at the center tap is 0v. Confusion
    abounds! thank you.
    How

  34. Why do assume that electrons exist? A Nobel prize does not prove it; neither does consensus. Tesla, Heaviside, JJ Thompson (pre-Nobel) and Steinmetz did not believe they do.

  35. so.. electrons actually move like water-flow in the wire? don't they move like wave? the speed of electricity is actually the speed of electron wave (either vibrate up-down or left-right)

  36. I can almost go along with this "slow as molasses in January" electron flow notion, then I think of lightning…Lightning currents are understood to be pretty high…In electric discharge, what is the "conductor"? Do insulators become conductors at extremely high voltage? You know, the implication of this explanation is that batteries don't supply a surplus of electrons!!! Isn't that a problem?!

  37. if current moves so slowly what do we see in an arc, such as arc welding? if the electrical charge is being transferred to electrode > air > steel weld puddle > work material > return terminal

    the it should surely be moving incredibly slowly. But that jet of a plasma arc looks so damn fast.

  38. So in the AC circuit, there is no + and – like in direct current. That is exactly what is taught everywhere. although you clearly avoided saying it. You know where this is going. 🙂
    Why then in real life in the real world, we have a hot-wire and a ground/neutral or whatever lingo they want to stress me out with, and we better know the difference. Worse yet dirt/earth is the conductor and when you walk on it, you are not dead on the spot or the whole population for that matter. Oh god here comes the explanation. I am not sure if there is enough room in here to convince me. So far everyone has failed for the last 20 years of inquiry.

  39. I like what you said about careful word choices..its often odd how an "English Major" might say they dont need science and how a "Science Major" might say they dont need to study speech or communication skills. When you get down to obvious that's the reason why things work or dont work….

  40. hi thank you for youre great teachings,can you add to this and explain the mechnisium that occure around the wire has plasmonic resonance and the interactin with the metal and the enviroment. i understanding it in phylosophical ways that givesme certain results and observation to work with. in any case if you can add to it so we can more indeeped try to conceive all the processes occuring in a very simple and advanced way.like you so good at explaining. resolving the language and making sure we have the right terms o should i say speek of it so we can understand more principal. i notice current is not of top choice if we to explore all aspect of what is occuring, photon proton ,plasma,ion,and so on. thank you so much i will study youre video and make sense of it all,if you can explain what you can about it.in a all around most advanced way you can conceive,i can help in my own way of understanding it. i am working on resolving a greater perspective to include all that needs to by studied and taught on galactic scales. lol thank you for your amazing share, blessing to you for such openess in sharing.

  41. But do electron holes really flow?
    And what is the sound of one hand clapping? Where was I going with this? Who stole my pants?

  42. Given I now know posting comments with URL's can create an invisibility situation, here's a modified version with no URL refs:

    Nick, your 'slow as molasses' claim re drift velocity of metallic conduction electrons is very widespread even in textbooks but is out of date by nearly a century. Sommerfeld overthrew that old Drude model back in the 1920's. Replacing it with a QM one where a relatively small number of conduction electrons moving at near the Fermi speed ~ 10^6 m/s have their angular distribution of velocities far from random and heavily biased to along the applied E axis. A web search for e.g. "Drude vs Sommerfeld models for metallic conduction" will yield useful articles going into various levels of detailed theory.
    Even 10^6 m/s is only a small fraction of light speed, so that won't explain 'instant on' which still needs surface wave coupling, but nevertheless the true picture is far different in detail to the stubbornly long-lived Drude one.

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