EEVblog

[@guillaumeerard]

I have no interest whatsoever in EE but I find your videos really compelling! I am so glad to live in a time when people with your enthusiasm can have the means reach out to so many people!

[@russelltennis15]

Why am I paying $20,000 a year to learn electrical engineering at a university when you explain it better?

[@AIArchiveLabs]

Danny Russell A lot of universities have professors thats sole purpose is research and not teaching.

[@jeffbrubaker1748]

Danny Russell wait till the full economic effect of that are realized. I love this guy.

[@WilliamMcCormickJr]

Brendan Raymond Actually years ago Universal Scientists who were almost always college professors or consultants to colleges, used to visit honor science classes in public schools. In 42 minutes they gave the entire class an understanding of the universe. I will admit that for weeks to come I was in a mild state of shock, however it was a healthy state of shock. I had things to check out and I did. And sure enough these guys were spot on. Unfortunately one year, I was in the fifth grade, in 1972 while we were getting a college lecture from a universal scientist, he informed us that as of next year 1973 it would be illegal for him to teach the atom, at Federally funded schools. Because the federal government education system had adopted the neutron and attraction forces, as being real. He wished us luck and told us that we had all we needed to make it through the rough times that were coming. For a while I tried to focus on school, however they started changing our science equipment and even chemical formulas on chemicals. In one year I had to learn two different markings for two similar cathode ray tubes. I started losing interest in school. About two years later one of my science teachers said that I had to enter a science fare project or fail my class. So I built a working solar house, and took a second place at my school science fare. My science teacher then said I had to enter it in the Long Island Science Congress, Science Fare at C.W. Post college. Begrudgingly I did, I took a first place and won a scholarship to C.W. Post college. But I had no interest in school anymore, so at 15 about two years later, I dropped out of school and started working full time. My point is that we are functioning at 10% right now. What we have done with science already, and hidden, is the other 90%. The problem or the truth is that matter is not what you have been taught it is. It is just an electrical effect. There is one sub-matter particle in the universe, the particle of electricity or as it was called, an atom of electricity. The atom of hydrogen is the smallest part of matter. An atom of iron is the smallest part of a piece of iron. The word atom used to mean the smallest denomination of a substance. Our problem is not actual science and reality, it is poor leadership and education. In other words science is rather easy and fun. The politics blocking science is not easy or fun. Americas first president said this "There is nothing which can better deserve your patronage than the promotion of science and literature, knowledge is in every country the surest basis of public happiness." George Washington. What Benjamin Franklin knew about science and weapons would shake our military today.

[@martinda7446]

Danny Russell Please tell me that a someone learning electronic engineering at uni is not needing this.

[@WilliamMcCormickJr]

mart fart There is a difference between memorizing things they teach you and understanding the actual basics that make them work.

[@EEVblog]

I did not slip up on the term. The term "through" is defacto standard in the industry and used in many aspects of teaching.

[@DjVortex-w]

So the simplistic answer is: Do electrons flow through a capacitor? No. Does current flow through a capacitor? Yes. One circuit can affect the electron flow of another circuit even if they are not physically connected. That's how eg. transformers work.

[@mrslovvet]

Wow, that's such an obvious way of saying it, but I never thought about it like that. Thanks!

[@TheVirIngens]

Transformers do work as you explained, but it's important not to confuse magnetic and electric fields, inductors and capacitors etc. transformers have no (intended) capacitor and have practically nothing to do with this video.

[@HitAndMissLab]

I would say that much more accurate is to say that "electric field travels" through capacitor, not a current. Current is dQ/dt and right in the middle of capacitor, where dielectric is, there are no charge carriers. If there are no charge carriers, there can't be a current. In other words, the dQ=0 so dQ/dt = 0. Current is not flowing inside capacitor, but electric field is pushing charge carriers outside of the capacitor. What Maxwell did with displacement currents is just a modeling trick to balance out the equations. For all the practical purposes it does the job.

[@antigen4]

or rather more simply - it's an electric field that does the work of a capacitor but NOT a magnetic field as in a transformer. With a transformer - we have electricity converted to an INDUCED current via coils which generate magnetic fields (hence the ability to change voltages across the gap by induction. But with a capacitor, there is no associated magnetic field created beyond what you get traveling through the connected traces or wires. Otherwise you would see capacitors exhibiting magnetic behaviours when you turn a circuit on.

[@antigen4]

HitAndMissLab actually - i wonder if it would be provocative to suggest that YES - current flows through a capacitor - but VOLTAGE does not (?)

[@EEVblog]

Bingo, you said it yourself, the displacement current does go "through" the capacitor. At no time did I ever claim that electric conducted current flows through the capacitor, it of course does not. I did not "misspeak" because the term "through" is the accepted term in the industry and in many aspects of teaching.

[@LuckeWent]

I would also describe James Clerk Maxwell as an incredibly smart dude

[@mmichaeldonavon]

About 50 years ago, I was in a class that discussed, "Capacitors, does current flow through them?" The answer: "A capacitor BLOCKS DC, and passes the "EFFECTS" of AC." Simple as that. As AC is applied to a capacitor, electrons LEAVE one plate, and ACCUMULATES on the other (via the AC power supply) - when the AC reverses, electronics again leave one plate and accumulates on the other - back and forth. It will APPEAR that the current is going THROUGH the cap, but it is not. Yes, there will be DC current, momentarily, in a series DC circuit with a cap and resistor, as the current from one plate leaves that plate, and heads for the battery - then EVERYTHING stops! The DC is NOW blocked. Apply AC, to that same circuit, then it will APPEAR that current passes through the cap but, again, it really does not.

[@hcetink]

This answer Michael is more correct to me. Dave is obviously a sharp cat, but his answer sounds more philosophical.

[@bajatoma]

I agree, Michael. The way I think - it's like electric field crosses the capacitor to push those electrons from another plate, to leave wholes, instead of electrons. Up to a point where there is nothing to push (no free electrons in the capacitor's plate), and thus current stops. So, in AC, when the electromagnetic field is reversed, the capacitor on one side has too many electrons, and on the other side, too few. So, electrons don't pass capacitor (in an ideal capacitor), but the electromagnetic field does pass through to affect electrons on another plate of the capacitor thus making electrons move, thus creating a current. Another point - any broken wire is a capacitor. Except that capacitance is so small, that it's not being considered as a capacitor. So, just blindly saying that current goes through a capacitor is like saying that current flows through a broken wire. so, the answer is a bit complicated. So, technically, current doesn't flow through a capacitor, electric fields does, affecting nearby electrons up to a certain distance).

[@johnyang799]

@@hcetink He explained the same thing. No difference. In my words, current yes, electrons no. And an animation will be a better explanation.

[@hcetink]

@@johnyang799 uhhh ..... have you ever swam in a current without water?

[@johnyang799]

@@hcetink Current is electrons flowing doesn't mean it has to flow through! Using your analogy, if there is a way that controls the water on one side of a barrier and controls the water on the other side. The current/information is essentially flowing through. But not the same water flowing through. Understand?

[@Airbag1010674]

Dipole excitation is how displacement current works. When you apply an electric field to a dielectric it realigns (rotates the dipoles). This rotation of dipoles in response to a sinusoidal voltage is how a perceived current propagates through an insulator/dielectric. A good analogy is doing the "Wave" at a sporting event. Even though the wave moves in series, no one actually physically touches each other. This is also why capacitors block DC current, because there is no "force" to rotate the dipoles.

[@hellnawnaw]

Thank you so much for all of your videos Dave. I'm an electrical engineering student in Germany, and I'm in my second semester right now. Even though I've been doing electronics as a hobby for 3 years now, and even designed a board for money already, I always learn so much great stuff from you, which helps me very often. For example, your soft switch tutorial inspired me to create a RS-flipflop softswitch that can be turned on by a button and turned off by an AVR which can also read the button.

[@DragonHawk379]

I see it this way: current flows into a cap, and back out rather than through. In the demonstrated DC circuit with a switch on one side of the cap and the other side grounded, (conventional) current flows into the + side of the cap. Hook up a resistor across the cap and the current will flow back out of the + side of the cap. Presumably in the ammeter demo at the end of the video, a second ammeter on the grounded side of the cap would show no current (since that side always stays at the same voltage, ie: zero), hence the terminology of "into" rather than "through". Of course here we are talking about an ideal cap with no leakage etc.

[@weylin6]

How was there any doubt of this?? Take this comparison, using a hydraulic model: You have two pre-filled pipes leading into a chamber, in the middle of the chamber is a flexible diaphragm separating both pipes. normally, both sides are in balance, but when a pressure is applied to one side, a voltage, it pushes the diaphragm, inducing an equal current on the other side until the inflow has stabilized. Correct me if that is an incorrect way to look at it, though.

[@davidb5205]

+weylin6 This is the explanation that finally made me intuitively understand what a capacitor is after four years of college. The flexible diaphragm constantly moving back and forth provide the appearance that the current is flowing through barrier when it is just an equal response to the change in movement. No change means that stable, steady, not moving and basically current less.

[@steveseifer6784]

+weylin6 When "pressure is applied" in your analogy infers a changing pressure which is alternating current. We know that a capacitor does not block AC of adequate frequency but completely blocks a continuous level of DC current since this DC current immediately starts to drop as the capacitor charges. Electric Current will stop flowing but the displacement current is another subject. Any device needs that Electric Current even though this thing called displacement current is existing. It really depends on what we are talking about.

[@runningbear4666]

+Steve Seifer buy today pay tomorrow

[@tarstarkusz]

When I was in electronics classes in college (I've really not used it since), I built circuits that used in series caps to disentangle DC from AC. The DC was effectively blocked while the AC flowed straight through. Obviously I did the choke to do the opposite and allow AC to be disentangled from DC and effectively blocked the AC. It was really while learning about chokes that magnetic fields came into play. So why did my circuit work, presumably?

[@tarstarkusz]

I understand that that AC is not truly passing through, but is due to the reversal on AC. What I don't understand is why my circuit supposedly worked (disentangling DC from AC) if caps pass DC current through an electromagnetic field in the cap (which is what he appears to be saying). Is the AC collapsing the DC EMFs?Also, I noticed his current meter went up, then went down and stayed down. I know it can take 5 seconds or so before a cap fully charges, but it was at least a couple of seconds on 0 after that initial sharp rise. I double checked, the circuit was still closed. If you offer any assistance in this, I'd greatly appreciate it..

[@LeeMaitland]

REVELATION! When you did the dQ/dt and explained it as 'change in charge over change in time', suddenly six months of calc just made sense! THANK YOU!

[@joeyoest1105]

Quote of the day: "Does current flow through a capacitor?" *touches lead to battery - ammeter spikes* "Yep! See you next time!" Made me lol!

[@MrJuancho011]

The best ending for this video! he made me laugh. excellent !!!

[@EEVblog]

When did I say it was electric current flowing through? Yes, the practical demo was meant as a joke.

[@pcguy619]

If you want to see a good argument, put a physicist and an electrical engineer in the same room and ask them their viewpoint on this topic!

[@eqlipse333]

From a physics standpoint, there's a very easy way of looking at this. "Energy" flows through the capacitor; the first plate, while charging, produces a magnetic field, which in turn generates an electric current on the other plate, thereby allowing energy to flow from one plate onto the other, even if the electrons themselves are not. If you think of it from the abstracted view of "energy," which doesn't necessarily have to be held by the electrons themselves, but any combination of the electrons and their electromagnetic fields, then it actually becomes rather simple.

[@foxyrollouts]

interesting concept

[@BMan18]

Come on, press the envelop. Let go the concept of a fundamental particle and embrace the reality that everything is an electric field, just balanced in different ways that limit and control the interactions with other fields. You just might come to realize that magnetic fields are like shadows... but that's for the advanced class. Meanwhile you can begin to distinguish the actual field attributes and how to take full advantage, unlimited by the artificial restrictions of particle physics.

[@wietse6672]

Yes! It's good to keep the goal in mind: why are we moving charge through the circuit? Just to move energy to do some work elsewhere.

[@simonruszczak5563]

@BMan18, I agree most of fundamental physics is still wrong. . . I've come to the conclusion that our "reality" (energy/forces and matter) is fundamentally the movement (waves) of aether, which is everywhere, even in "empty" space. . .We don't really have physical substance, the aether does. . .Nikola Tesla know decades ago.

[@Kris_M]

+eqlipse333 No magnetic fields are involved. Applying a voltage across the plates allows electrons to be added to one and subtracted from the other.

[@proyectosledar]

I'm sure we are learning something. thanks dave

[@nope1906]

Love the enthusiasm that you approach these fundamentals with! You have a real talent for explaining concepts of EE.

[@Minastir1]

You don't actually even need to understand how a capacitor works to answer this question. If you replace the capacitor with a mystery component X which attracts electrons on the other side and repels them on the other side the current still flows. What's happening inside this component X is irrelevant.

[@marklvrd]

actually...current does not physically flow through the capacitor. The whole circuit is set up by an electric field, there is an electric field induced inside of the capacitor, not actual current.

[@wbeaty]

The *electrons* don't physically cross the gap. But what about the current? (Does the word "current" really just mean "moving electrons?" Always?) For example, is there a current just in front of each flowing electron? And just behind? A clamp-on ammeter says yes. A clamp-on ammeter thinks that electric currents are a particular type of magnetic field: the relative change in each electron's moving e-fields. The ammeter doesn't have to detect each electron. Instead it just has to detect the motion of the radial e-field surrounding each electron. If we look at things in this way, then whenever a cloud of electrons is moving, the "current" isn't concentrated inside each moving particle, but instead fills the space between them. If we look at capacitors from this viewpoint, then the current fills the capacitor's dielectric gap, since those changing fields extend out ahead of the electrons entering the negative plate, and also extend behind the electrons leaving the positive plate. Get a capacitor with a wide gap between its plates. Apply a high-freq AC current. Slide a clamp-on ammeter along the capacitor terminals, and across the gap. The ammeter cannot see the gap. It thinks the current is continuous.

[@docdaneeka3424]

Hey it's wbeaty! I remember your website from nearly 20 years ago! Your pretty much right we can pretty much consider current to be where ever we have a magnetic field, which includes the displacement current in the gap in a capacitor. There *really* is a magnetic field in the gap in a capacitor because of the changing electric field. if you were to put a wire there, 'electron' current would flow (imagine putting two extra plates inbetween connected to give you effectively two capacitors in series. charge moves from one plate to the other as it charges. there really is current in a capacitor!

[@marklvrd]

wbeaty Yes current is the amount of moving charge per cross sectional area, if you look a certain distance in the capacitor you will not see current on the phyiscal level. What you will see is an electric field in the gap wether it be air or a di-electric with ions. Also it doesn't matter if the ammeter cannot see the gap, what do you think a battery is? Batteries induce current via electric field, those electrons are not in the battery, they are in the wire itsself.

[@wbeaty]

You will find Maxwell's Displacement Current, the fundamental discovery which led to all modern EM technology. Displacement current is the same as all others in that a clamp-on ammeter measures it as current. It's different in that it's part of the fields around moving charges, and not described by the charges themselves. In SI definition of Ampere, the definition involves forces between currents, *not* amounts of coulombs transferred over time. So as we define "amperes," displacement current produces real forces just like any electric current. Of course these forces originate in the increasing charge on the capacitor plates. When a capacitor plate has an increasing charge, we find displacement current in the plate, in the adjacent dielectric gap, and in the capacitor lead wires. But no moving charges in the gap, if a vacuum capacitor.) > Batteries induce current by electric fields Wrong. They induce current by charge-transport, same as any power supply. The moving charges are in the battery electrolyte, as well as in the connecting wires. A battery is inherently a conductor, with a short circuit between its plates (conductive salt water or acid, etc.) Don't be misled by erroneous grade-school textbooks which erase the current between the battery plates. To learn correct battery physics you have to go to college-level texts (and un-learn the incorrect garbage we were taught about batteries in earlier grades.)

[@TheAudioGarden1988]

I'm soon to begin studying a HNC in Electronic Engineering :D And having these videos available so freely is incredible! I love that we, in this day and age, can hear from passionate, knowledgeable people, the world over!!! It's such a huge benefit over having to hope that you have a tutor who is passionate enough to not kill your fledgling interest in a subject! Even bad teachers can now be offset by the passion of those who wish to share theirs with everyone else! :D

[@EEVblog]

Yes, a lot of repetition in this one is obvious when I rewatch it. Wasn't that obvious in editing.

[@mennims]

Dave is a sweet person. I'm glad to share the world with wonderful people like him. Thanks for all the knowledge and memories

[@moyrml]

Why is it so hard to explain? You have electrons building up on one plate and their electric field repels the electrons of the other plate. Moving charge, and thats current. Isn't it... it?

[@suzesiviter6083]

moyrml: Thats a chicken and egg situation, its hard to imagine 'spaces' moving, so its better to use electrons in the description.

[@leroycasterline1122]

Another gem from Dave - displacement current - brilliant! I was on the 'No' side of this question (and still am to the extent that electrons don't physically pass through a cap) but also understood that the practical answer was 'Yes'. Now I have a name for the current that flows while a cap is building its static charge.

[@klodiklodian1190]

The answer is simply, as it turns out no actual current (or electron flow)makes it across the gap, at least in an ideal capacitor.Nevertheless clerk maxwell noted that even if no real current passed from one capacitor plate to the other,there was a changing electric flux through the gap of the capacitor that he believed (and proved) that it permeated the empty space between the capacitors and induced a current in the other plate.this curren is known as displacement current (Id)

[@EEVblog]

Agreed. Nothing short of pure genius. Probably one of the greatest discoveries of all time.

[@WhoWantsToKnow81]

Fantastic, now every time I read a circuit, I do so in an Aussie accent. :D

[@pnogas]

I love the ending. Throwing the marker in the air. Then actually connecting the circuit asking the sarcastic question. Priceless.

[@probablystalkingyou]

Love your enthusiasm.

[@trueslashcrack]

Thank you very much, Dave. One EEVblog video is worth more than 3 hours of school lessons.

[@DavidSprings]

You'd be more credible if you sat next to a workbench with an o-scope showing a sine wave. Throw in a brand new soldering iron and a power supply for extra gravitas.

[@zerog2000]

Lols. +1 for batteriser ref

[@travisbutler2014]

Dave said voltage charges up in a linear fashion. From my understanding voltage doesn't charge up in a linear fashion in a capacitor, it charges exponentially depending upon the time constant (t=RC) This can be calculated in increments of 5t. It is also possible to find the instantaneous voltage at any point with this formula if increasing and beginning at 0v: v=Vf(1-e^-1/RC) with RC being one time constant.

[@erics8326]

When he said that he was showing a circuit with an 'ideal' current source connected to the capacitor. In this case, the voltage would charge linearly since the current is linear. However, if you were to look at the voltage across the current source it would not be linear, it would be exponential.

[@agnichatian]

(commenting to you Travis) The voltage across the current source is the same as the cap that it is across, as they are in parallel. However, you are correct that a constant current source would ideally (if it had infinite voltage available and the circuit could take it) drive the voltage across the cap LINEARLY, not exponentially, described by the eq. v = i*t/c. This formula also shows that the voltage rises linearly with both current and time, and that the larger the cap, the slower it'll go. Also, even if a series resistor were inserted, the voltage on the cap would be identical. The exponential formula applies when it's a voltage source and there is a resistance for that voltage to divide across as the cap charges.

[@railspony]

"and you can spend years and years of your life trying to understand how, or if, current flows through a capacitor." No thanks, I'll just trust I_in -> I_out. I learned my lesson on the difference between practical circuits and physics because when I was a kid and thought current was backwards because electron flow, and then later I learned about holes as charge carriers and realized oh, current doesn't actually mean electron flow after all, and those engineers aren't a bunch of idiots. Who knew?! LOL I really liked the brute force proof at the end. The video would have been less fun with that at the start.

[@johndoe-gr3mj]

Dang. Dave, I wish I lived across the street from you. What thrust me into my obsession with electronics fundamentals was my attempt at using a dynamic microphone on a hardwire telephone. I ran into a problem until a docent at the Pacific Bell building museum on 2nd street in San Francisco informed me that the telephone volts were clobbering my dynamic microphone and that I should use capacitors to prevent it. I ended up using one 22 microfarad capacitor on each pole and the result was magic. I still had problems with the receiving end of my phone calls but I'm sure that I could have worked it out. But I had a lot of fun and I got to gain knowledge about microphones.

[@stancurtin]

A dissectible capacitor is a beautiful thing to behold, and further convolutes this issue and leans away from electromagnatism and how charges are stored and where... There's a wonderfully WEIRD video from MIT right here on youtube if you use search term "MIT Physics Demo -- Dissectible Capacitor". Take a peek for fun!

[@fredbrooks9496]

It's only WEIRD if you don't understand how it's easily explained by simple physics. The MIT guys were having a bit of fun with the naive.

[@stancurtin]

fred brooks Are you saying the video was a fake? I've read about this experiment enough places to have taken it for fact. But, I do have all the gear here to put it to the test if you're telling me these videos and accounts are hoaxes...

[@fredbrooks9496]

It's not fake or a hoax. It's a running joke that hides the fact that the surface charge (on a thin film of water from the air as the conductor) on the glass inner and outer surfaces receive the charges from the metal plates when they are removed (via high voltage corona discharge) and hold the energy in a electric field with the glass as a insulator (not a dielectric) and is transfered back to the metal plates when reassembled.

[@stancurtin]

fred brooks That is absolutely fascinating! Thanks for that explanation. I had heard that Franklin fooled himself in doing this experiment, but never heard the reason why. I'm currently reading 3 books on electrostatics as it's something I've had a long term hobby interest in (I also do a kids electrical show with tons of HV gear). I do see claims, in several places in the books I'm reading that charges are in fact stored in the dielectric and not in the plates. I love to experiment. If I were to reproduce the MIT experiment, but heat everything up as hot as possible with a heat gun to avoid moisture, would that be a good control to eliminate the possibility of moisture? I do also have a vacuum chamber where everything could be placed after heating, but it would be more of a pain to rig... Would I be wasting my time?

[@balancedjourneydiaries]

you explain it so much better....much better than sitting in a 2 hour lesson...

[@EEVblog]

Yes, I can. And yes, I did.

[@brockm4047]

Dave, thanks a million for this and your other videos! This was helpful and made perfect sense to me. I have been a hobbyist in electronics for 20+ years and hate to admit it but you have forced me to rethink what I thought I knew about such a basic component. Cheers

[@an_R_key]

Asterisk is the little ASCII character and Asterix is the cartoon character ;-)

[@EEVblog]

Yes, that simple explanation is indeed very useful for understanding how a cap works in terms of charge build up, and if you want, how current flows "in and out" but not "through". And I would have used that in a basic how how capacitance video and nothing else. But with this video I wanted to show there is a deeper mathematical theory and a different "type" of current many people may not be aware of.

[@gramplifier]

Good video Dave but I always teach that inductors work by electromagnetics and capacitors work by electrostatics. You said, quite correctly, that electric current is the flow of electrons. If the electrons are not moving then there is no electric current. Consider now the following analogy which I use for teaching how capacitors work. Imagine a shopping Mall filled only with heterosexual men, who represent the electrons on one plate of the capacitor. All of a sudden a naked lady appears (+ charge) in a shop window. All the men rush to the window and because they move there is an electric current. Quite large at first but tails off as the furthest men get to the window. The glass window (insulating dielectric) stops the men touching the girl but because the Mall is now devoid of men (negative electrons) you can say that the Mall has attained a positive charge because of this.Now you change the polarity, we can do this in the analogy by replacing the naked lady with a naked man! The men zoom away from the glass window, creating a reverse current flow, back into the Mall, so making it negative. So with this simple analogy, one can see how a + and then - charge on a capacitor plate can make the electrons go back and forth, creating a current even though non of the electrons actually go through the dielectric. It's not a perfect analogy but always causes a laugh in the classroom and gets the students attention. :-)

[@jonasdaverio9369]

Woow, I had never read any such explanation.

[@WilliamMcCormickJr]

Les Carpenter, the problem with your analogy is that if you hold the (+) charged side of the capacitor to the (+) charged battery terminal voltage by attaching them together, when you connect the (-) charged terminal of the battery to the (-) charged terminal of the capacitor according to your theory none of the particles of electricity from the (-) battery terminal should make it through the capacitor, yet they certainly will. When they changed Ben Franklin’s markings on a battery they really messed things up nicely, that is what caused all the confusion.

[@EEVblog]

Yes, "it depends". It doesn't matter how you define your boundry conditions in fact, displacement current can still flow cap "through" the cap in either case. If you don't want to talk in terms of displacement current, and only electric "conducted" current, then no current flows through the cap.

[@AlexChama]

I ADORE your videos! EE used to bore the crap out of me, in school it even intimidated me, although the actual building and soldering in itself always seemed interesting. Then I got into repairing game consoles and such, I became more interested in the actual theory behind all of this thanks to your channel and this is one of those videos where I can proudly say: Learned and keeping more from this short video than 1-2 lessons in Physics. Go figure. I'd have loved to have you as a teacher and some more motivation and goals back in high school. :)

[@zaphhood4745]

You just did in 15min what my teacher spent 3 hours on. Nicely done. Thank you Dave.

[@mybluemars]

Displacement current flows but electric current does not flow through a capacitor.

[@Daweim0]

Well, if you want to be specific, if you put n electrons into a capacitor, n electrons will come out the other end, but they will not be the same electrons that you put in. So yes, one could say that no current flows through a capacitor because no electrons go all the way through a capacitor. However, seeing one can't id individual electrons (and even if you could it would be a waste of time), there is no effective way to tell the difference. Electrons go in, electrons come out, current flows.

[@xxJerry19xx]

If you will take LED, resistor, battery and big capacitor and connect it all in series you will see that led will turn on for a short time. So current is flowing. Same thing like at the end of video, but LEd instead of meter. What else you need to know to convince you that yes current flowing thru cap. Current flow from battery, LED, resistor to capacitor and than out from capacitor back to battery. So what is going on in capacitor ? Current using teleportation from one electrode to another ? Doesn't matter, same current goes in as goes out. So You can tell that it flows thru. And If you wil take compensating capacitor for example from linear fluorescent luminare (classic one with magnetic ballast) and connect it in series with light bulb (not powerfull) and connect it to 230/110V AC 50Hz bulb wil glow. In AC circuits you can calculate Z or Xc of capacitor.

[@kevinobrien8803]

Current does not flow. Current is a name that means flowing. And is a term that is used to represent the charge flow rate. In Coulombs per second. So to say "a current flows" is the same as saying "The rate charges flow flow" which does not make any sense. But amazingly everyone keeps saying sentences like "current is flowing". Which will be totally confusing for beginners. It is only charges that flow, never ever current. Its as wrong as saying "a river current flows". Also displacement current is the term used to describe the "rate of change" of the electric field between the plates of a capacitor. For example in an air gap capacitor there is no polarization current (dielectric charge effects) at all. So its all just dE/dt only, which itself comes about from the changing PD between the plates. That is all that displacement current means.

[@shamelsanders1591]

Kevin O'Brien so if current doesn't flow what does it do?

[@kevinobrien8803]

Shamel Sanders Current means 'charge flow'. So if you see a sentence in a text book like so "In the circuit there is a current of 4 amps" That is perfectly correct. And is just another way of saying "In the circuit there is a 'charge flow' of 4 amps" which is also perfectly correct. But if the sentence in your text book (sadly many of them make the same mistake) is like so "In the circuit there is a current flow of 4 amps" That is incorrect use of the English language, as it translates to the following. "In the circuit there is a 'charge flow' flow of 4 amps" It is not that the person who writes or says this does not understand about circuits etc. Its purely a semantic error only, but one that is very difficult if English is not your first language. It might seem pedantic to pick up on this, but I think it is important for many who will be confused by this wrong use of the English language. So the following examples below, are all incorrect uses of the word current. I have added a correct usage afterwards. (Looks like many comments on this video is making same or similar errors) In every correction below, if you just substitute the word "Current" with "charge flow" you will see they still read correctly, where as the ones I am correcting you will see very clearly (if you make the same substitution), that they are all grammatically incorrect. here is an example where the same error has been done twice. "Displacement current flows but electric current does not flow" A proper way to describe the above is as follows: "A Displacement current exists but an electric current does not" Here is another wrong sentence "Does current flow through a capacitor" Here is one correct way to describe that. "Do capacitors plates have a current between them" here is another wrong sentence "current never flows through the dielectric of the capacitor" And the correct way to express that meaning. "Current does not exist within the dielectric of the capacitor" etc etc.

[@JerryEricsson]

Sure am glad Christmas is just around the corner, every time I watch your videos, these BELLS ring in my head as something sort of comes around and flows properly. Thanks for teaching me a bit of electronics every day.

[@makutingting]

so how come you do not specify current ratings when buying a capacitor?

[@UnbornWarrior123]

Current ratings are specified in terms of temperature raise...

[@whitcwa]

It is incredible that Maxwell did his work before the first electric utility was built.

[@MrHydroguy]

Its not flowing through the capacitor.its charging the surface of the positive side of the cap. Then when its fully charged no more current builds up until its discharged again.

[@yalgret]

MrHydroguy sure the electrons don't accumulate on the negative? Conventional current is wrong.

[@Kris_M]

It's charging both surfaces (one subtracting and the other adding electrons). +johnDon No electron accumulation was mentioned though.

[@slartibartfastm9714]

If the current is not flowing through the capacitor we should be able to disconnect one side of the capacitor from the circuit and it should work the same way. BUT in that case the capacitor dosen't charge, why: because the freaking current has to flow through the capacitor!!

[@danielstimpson7792]

totally agree

[@Shim267]

Dave plz... muh' mind! This field never ceases to amaze me.

[@BogdanSerban]

I've gone through semesters of electronics in middle school, high school and university and nobody was able to explain which is the actual direction of current flow. Until I looked for an answer on youtube and kind of got it. Having diplomas and degrees only means you know formulas and how to work with electronics, not that you have the absolute understanding of what's happening.

[@steve24822]

That's a shame you had that experience. When I was doing electronic engineering at the university of kent it was one of the first things taught and explained very clearly. For circuit anyysos and design we used conventional current flow but were taught about actual current flow in solid state physics.

[@docdaneeka3424]

Having diplomas or degrees means you have diplomas or degrees. It means you are SUPPOSED to have an understanding of what's happening. Whether you do or not depends on the quality of your teachers and the quality of your effort (which is largely dependent on your interest).

[@mayito714]

We learned electric current flow the 1st day of introduction to electric circuits 101. The electrons, the charge carriers in an electrical circuit, flow in the opposite direction of the conventional electric current.

[@wbeaty]

"Actual" charge flow is too complicated: electrons flowing in metals, protons flowing in battery acid and in proton-conductors. In salt water it's flowing +Na and -Cl ions. In alkaline electrolyte it's -OH ions. In wet dirt and in human bodies it's +Na and -Cl ions, same as in salt water. In sparks and gas discharge it's electrons flowing one way and positive ions flowing the other, going past each other in opposite directions. Cont... So, which is the REAL direction of electric currents? (The answer must apply to conductors, not just metal wires.) Think carefully: when you're getting electrocuted, no bare electrons are flowing in your body, but opposite-charged ions are flowing in two opposite directions. Physics has the answer: we hide the complexity behind a simplified concept called "Conventional Current." To do this, we add up all the flows to form a single current. For example, in wet dirt, if pos and neg ions are flowing in opposite directions, that means the negative charges that flow backwards must add together with the positive charges flowing forwards. (A double-negative makes a positive current, so negative charges, flowing backwards, will give the same amperes as positive charges flowing forward.) Wet salty ground has a single amperage made of conventional current. (We don't need to think about the many charge flows in the dirt: the +Na and -Cl and +K and +Mg and +H and -OH.) For those who want the REAL currents, and not the simplified version, it's not enough to just say that "current equals electrons." Current in copper wires is actually electrons flowing past positive copper ions ...so if we move the wires backwards at just the right speed, then the electrons stop moving, and the electric current is now composed of positive copper ions going backwards! (See, the REAL current was never just a flow of electrons. It had always been a *relative motion* between the copper atoms' nuclei and the copper electron clouds.) Conclusion: if we want simplicity, where we just deal with a wire's volts and amps, then we use Conventional Current to hide the actual charge motions. But if we want reality, then we'll end up with Ben Franklin's Kite String, the famous twine which is an acid-based conductor. Ben Franklin's kite string used +H ions as its charge carriers. Only the protons were flowing along his twine, not electrons. (Heh, so when Franklin assumed that the charge-carriers within conductors were positive, HE WAS RIGHT?!)

[@mayito714]

Do you think that learning from the internet will make you an electrical engineer (EE) in time? Have you seen the curriculum of (EE) from a major university?

[@EEVblog]

Nope, I meant electromagnetic. If you go into the physics of it, it's a magnetic field that defines the displacement current.

[@TheAudioGarden1988]

I appreciate all your efforts Dave! :D I look forward to being able to increasingly understand what the hell your talking about :P

[@altuber99_athlete]

I haven’t watched the video, but in brief: • Conduction current flows through both leads/wires of the capacitor, but not through the dielectric/gap between the plates of the capacitor. • The conduction current in both leads is the same. • You don’t ever charge (add net charge to) or discharge (remove net charge from) a capacitor as a whole (i.e. considering both plates); the net charge of a capacitor is always constant. But you do charge or discharge the individual plates; their net charge does change with time. • Displacement current “flows” through the dielectric/gap between the plates of the capacitor, but not through the leads/wires of the capacitor. • The numerical value of both types of currents is the same in a capacitor.

[@thedivinityman]

Touch a cap that is in a high amperage circuit, that is fully charged, like the one that is hooked up to the magnatron in your microwave, and your corpse will prove that current flowed through that cap into your body and killed you.

[@libragirl8078]

I liked my humans fried, double fried like my chicken! hahhahaha! ;-)

[@marcellucassen8033]

All your proving is that current did at one time flow into the capacitor and at one time flowed out of it into your body and killed you ;) this video should explane it all, maybe watch it again?

[@mmichaeldonavon]

***** Har, har, har.

[@railspony]

OK, connect one side of the capacitor to your wall socket, and hold the other side with one hand. Now, ground your other hand and you'll know for sure if current flows through the capacitor, or not, because if the current flows it will roast you. (it will roast you, don't try it; use a meter like in the video)

[@mmichaeldonavon]

Really, no current "flows through" the capacitor, in an AC circuit. It just "appears" to do so. Unless a capacitor's dielectric is "ruptured," there is no current actually "through" the cap. It just "appears" that currect is flowing "through" the cap. The cap just "charges, discharges, charges (in the opposite direction) then discharges. Current looks like it is moving "through" the cap, but really is not. (yes, you would feel the effects of that AC :) An electrolytic cap, in a DC circuit, will pass "the affects" of AC, but will block DC. No current will actually "pass through" the cap. If there is an "AC ripple" riding on the DC value, the DC will be blocked, but you would see that ripple on both "sides" of the cap. Or, am I wrong? I

[@alext9067]

Dave, the definition of current is not really that any particular electron went around the circuit. It's more like a communication from one to another, so that the last one at the end feels the first one start to move. Like the many metal spheres that hang on strings and go click click back and forth. The middle ones never really move, but the end ones are communicating w/ each other. You said it yourself. Electrons move slowly. About a mm per second. Its the signal that moves quickly. Start throwing the tomatoes......NOW!

[@alext9067]

+Solar Species All well and good, thanks. It's been almost 50 years since i took basic electronics in college. I'm sure your right. I don't have the stomach to plow through it again. I was kinda addressing the philosophical question that Dave was asking. The answer is yes. And here's why. Current is in no way the electrons traveling around a circuit. If it were, then AC would have no current. It is the communication of field force. The force is continuous across the cap, so that's it in a nutshell. No math. No tears. Just a simple idea. Thanks for the reply. On the other hand. You are right also. A charged cap will block DC. Current will not flow. So should the answer be that it depends on the conditions of the current? I will leave it to you. I think you have a better grasp of the subject.

[@keyboard_toucher]

2:24 "The current starts off incredibly high because the capacitor's effectively a short circuit when you close that switch." This isn't quite correct. The maximum current is limited by the resistance of the resistor that lies in between the capacitor and the battery (and its voltage). If we remove all resistors and other components and simply connect a capacitor directly to a voltage source, then we can say we're charging a capacitor on a short circuit. But even in that case, while current flows through the circuit (i.e. through the wires), no current flows through the capacitor (i.e. from one terminal of the capacitor to the other).

[@calyodelphi124]

My mind is blown by this. I had trouble trying to wrap my head around why/how caps worked in series despite creating open circuits. Kudos to you. :) Could you do a fundamental fridays video about inductors, and one about RC, RL, and RLC circuits?

[@mmichaeldonavon]

Caps in SERIES is like ONE cap with a GREAT distance between the plates (the first cap's plate, and the last cap's plate) In PARALLEL it's like ONE giant cap with HUGE plates. So, in series, the capacitance will be smaller than the smallest cap. In paralled, they are all additive (their cap values)

[@dtiydr]

He could have said that magnetic fields are responsible. That would be a 5 sec long video.

[@EEVblog]

It can, as the switch in fact is a (small value) capacitor. But just like the capacitor you need a changing electric field in order for displacement current to flow. No more changing electric field (the switch capacitance is charged up), no more displacement current flow.

[@OzoneRush2007]

Hi Dave :) Love your blog! This is the frist time you have dissepointed me, there is too much wrong in this episode.. :( It is the physics that is the rule, but how you concider it in practial electronic is up to you. So as long as you don't have a dielectric breakdown, there will be next to no current flowing through the capacitor. You can only change the electric potencial over the capacitor, and that involve a current going in and out of the capacitor.. Keep up the good work :)

[@danielstimpson7792]

I agree with you

[@EEVblog]

Oh, but it's so much fun!, right?

[@BlueCosmology]

I don't understand why you've overcomplicated something so much that's clearly for people that are fairly new to the subject. Why you'd bring up displacement current without just mentioning electrons repelling is beyond me. (Especially when you don't even slightly mention what displacement current is. You just say displacement current flows therefore current flows without giving any reason whatsoever) The absolute exact same thing happens in a wire as a capacitor. Electrons repel other electrons, in a wire they move forward and since they repel other electrons those electrons move forward by the same amount. They move forward onto one plate of a capacitor and since they repel other electrons they repel the electrons forward off the other plate of the capacitor.

[@cobusvegmail]

+BlueCosmology That is exactly what I was thinking !

[@quadcatfly]

+BlueCosmology If that were the case, capacitor would be conductor no? Why does it stop repelling electrons on the other side?

[@BlueCosmology]

quadcatfly A capacitor is a conductor, electric current flows across it. Once the plate becomes charged enough, it requires too much energy to put more electrons onto the plate, due to the electrons on the plate repelling them away, so it stops conducting.

[@quadcatfly]

You should brush up on electric conductivity of dielectric materials. Especially the part where it says "dielectrics are insulator". All those electrons being piled up on one side of dielectric would immediately clot and prevent (e.g. repel) any new electrons from coming in, let alone push electrons from the other side of the plate (btw since when we have free electrons in dielectrics?). While you are contemplating this try to come up with explanation of how many capacitors IN SERIES could possible work based on your theory. If I place 20 caps in series the last in line would NEVER be charged because the first one (closest to -) will have charged and cut off the supply long before. But that is not how it works in a real world.

[@BlueCosmology]

"All those electrons being piled up on one side of dielectric would immediately clot and prevent (e.g. repel) any new electrons from coming in, " Yes, that is exactly what I just said. "let alone push electrons from the other side of the plate (btw since when we have free electrons in dielectrics?)." A capacitor is in its simplest form just two plates. Put one electron on one plate, it will push the electron off the other plate. Continue to put more on, you'll keep pushing them off the other plate, until eventually it takes too much energy to put an electron on the first plate. "While you are contemplating this try to come up with explanation of how many capacitors IN SERIES could possible work based on your theory." Completely trivially? There is nothing magic about putting two capacitors in series. The electron that is pushes off the first capacitor goes and charges up the plate on the second capacitor and so on. "If I place 20 caps in series the last in line would NEVER be charged because the first one (closest to -) will have charged and cut off the supply long before." That is nonsense. You put one electron on the first plate of the first capacitor, one electron comes off the second plate. The time it takes is irrelevant.

[@RTD553]

There's no magnetism involved here - just electric fields - so you don't really need to invoke Maxwell for a basic understanding. An electron arrives on one plate, and repels an electron from the other plate. So you see one electron go in, and one electron come out the other side. Do this with n electrons and this constitutes the current apparently flowing 'through' the capacitor.

[@pman1902]

Let's send him all our dried out old capacitors. You know the ones that let current go TROUGH them ;) Maybe he likes to use those ones. I prefer the new ones, you know the ones that DON'T let current go through them ;)

[@EEVblog]

Maybe, but that wasn't the point. Because the term "current though" is so commonly used and accepted in the industry, that I wanted to show that there is indeed a fundamental principle in physics and maxwell's equations that effectively allows (a different type of) current to "flow through" the dielectric.

[@JulesBartow]

Pull your head outta your asterisk Dave, You're confusing TO (not two or too) with THROUGH (not threw). TO! not through. 8+ minutes to get to Displacement Current. Charge flows TO the plates of the capacitor. Not through. OMG. Couldn't a cut a long story short... much shorter. Thank you for the effort anyway.

[@RandyLott]

Dave is absolutely correct. It requires the addition of charge density to really describe it. Schematic diagrams don't consider that current flows differently over different surfaces.

[@manwar999]

you must establish what current is first before you even discuss it...the real simple discussion should be '' DOES ELECTRONS FLOW THRU THE DIELECTRIC OF THE CAPACITOR'' the answer is NO...

[@JViello]

Old post, I know...if the current changes medium it's still current. I.E. Current in a wire being turned into radio waves, transmitted, received and transmitted back through a wire. Did the current actually flow "through" the air? Yes, yes it did. Just because it wasn't some visible plasma arc doesn't mean it didn't flow. Same idea here.

[@nishantyadav1793]

hattt be chutiye..

[@EEVblog]

Correct. No electric current flows. Please rewatch the video and see that there is more than one type of current. That was the whole point.

[@yadusolparterre]

For those who want to skip to the answer, the video starts at 11:40 Anything before that is noise

[@martingannon132]

I'm new to this channel and I always enjoy listening to Dave. You always talk about the the most important things keep it up!! And I think that you have a great way of explaining everything.

[@aeroscience9834]

Well, it is of incredible practical importance to people who invented or design capacitors. Also, I find I have a better feeling for the basic equations if I understand the physics involved.

[@foxyrollouts]

there must be a reason why they teach it. I enjoy maths in this regard as well

[@thedill1984]

You do an amazing job of explaining complicated theory in a form that is accessible to people who may not have had much formal exposure to training or education in this field. And this is an amazing channel overall - highly entertaining and informative - that I wish I had discovered earlier! Keep up the great work, you're a natural teacher!

[@kobraflyer]

+++ I really liked the last part where you use the analog meter. Says it all: Even that no electrons pass through the capacitor, there is current in the circuit. The electrons just flow back and forth during charge/dischage, and those moving electrons make up the current in the curcuit. It's all about how we define current.

[@BMan18]

NO! There are two kinds of current. Neither one transfers electrons. The science is so messed up. Charge current is actual movement of field potential. Displacement current is actual movement of field density. Think of it like one making room for the field, the other filling it. One will cause the fields around it to react to the distortion of space, the other will pass by without incident because it conforms to space. But that can be misleading too, its a metaphysical thing, electric fields. There are no particles. Matter is a a construct to make conversation simple. Magnetic fields are like shadows. They make things look different, but really aren't anything at all. All magnetic fields are the shadowy projection of moving charge fields which are making the structure of space. The whole equation that makes displacement current generate a magnetic field is a lie to cover up a bullshit theory about electricity and magnetism that is wrong. Don't be like these scientists, its OK to be wrong. Learn from it. Don't bury it in BS. What's really cool is you can squeeze field density out of the background fields that sustain our space by moving the moving charge fields. That creates an imbalance which precipitates field density. But they only last as long as you squeeze, so you have to trap and capture it in other fields. It's called induction, but Lenz's Law is a lie. That reaction only happens if you do a bad job of capturing the density field and convert it to a moving charge field immediately, like with a conductor with zero capacitance. If you squeeze that displacement current out, move it to a high capacity field structure, and then convert it to charge and get it moving you can then do it all over again without resistance. But not like they do today, not in the face of the field you just bent to force it go the other way. Move it elsewhere or delay the movement with capacitance and now you have it for free. Just like a sailboat moving across the ocean; capture the lift of the breeze but move on to fresh air. Ride the wind and the waves. Induction can capture energy without resistance just by transforming charge current to displacement current and back again at the right times in the induction cycle or in the right places so the fields don't conflict. But sadly, you will never see that while focused on magical electrons that are invisible and magically disappear and reappear in complete invisibility. All imaginary concepts that cannot possibly do what can easily be done. Try to imagine what is really happening with the components.

[@kobraflyer]

BMan18 Our definition of current is dQ/dt. A flow of charges. The charges are either electrons or ions according to our established physics model of matter.

[@BMan18]

Elis, Is "established physics model" supposed the mean right? Or are you admitting what you're saying is according to fairy tales, and truth is not about to be discussed or entertained here. I respect your right to be entertaining and say whatever you like. It's just not completely accurate. And it won't make or enable progress. Oh, and it leads to and supports the end of life on the planet unnecessarily. No biggy.

[@allesklarklaus147]

Man are you posting shit all over... Making weird claims, talking obscure things but nothing gets explained properly. just "yeah this dude shows you how it's done". Once you claim something proven right for quite some time is just wrong you gotta bring some nice evidence in. It's called science. Don't confuse engineers all over the place, go to a physics page and troll them. They have a better understanding and usually are more into "in-depth" discussion. These people just want to get their stuff done which they are perfectly able to with rules you claim to be so damn wrong.

[@BMan18]

alles klar klaus Sorry. Inconvenient questions are a bitch. I thought critical thinking was integral to engineering. Apparently your style is "do what you're told". I have a BSEE, and I managed for 30+ years to make a better than average income spinning the BS just like it was taught. Not much different than what was presented here. Then the internet and KZbin happened and I found the time to investigate those inconsistencies that I was taught to ignore. Guess what, not only are the inconsistencies deserved, the reasons why they persist go beyond science and engineering. So, the argument isn't about what is the right model or proof, it's about looking beyond models and demonstrations that are limited and clearly inadequate for how electricity actually operates. People who get this type of education need to know it's bogus. Then, when they can afford to cross their educators and employers, and raise their standards of morality to a higher than social acceptable level, begin their real education. If you know any real engineers, they will tell you what some of my mentors acknowledged: Every Theory has a hole. So they do what they have to, contrary to the theory, every day. What works rules. This has a limitation, it keeps things as they are, and it's far less than what you are capable of. You call it trolling, I call it spreading breadcrumbs to draw out the independent thinker. Why, because after a lifetime of working to keep things going the way they are, I've found out that its all a sham. Real electrical engineering can create energy without burning anything. And how can that be? You have to start by abandoning the flawed model of electricity being a mechanical system. You want proof? Play with magnets. They have fields that will act independently of their source fields. There is no direct mechanical feedback in that system, and that means no conservation of energy. But you won't develop it unless you understand how that can be. But there's more. And capacitors transfer energy without transferring charge. Charge is induced where the dielectric intersects the conductor. (This is an alternative model that actually explains how electrical fields travel through a capacitor.) This distinction of electric fields that does not carry charge does not exist in modern electrical theory. That theory is very inconsistent. It doesn't count the component and gets good results, but the component is there. Then there is a whole raft of demonstrations that may be using this as actual power. Look at the hairpin circuit and apparent potential-less power transfer. Or the aspect of induction of power but ignoring it in designs... there's so much. No time. Check out Distinti on KZbin. Eric P Dollard and Peter Lindemann from Borderland, the late Joe Bedini, Edwin Gray, so many more if you want proofs and even some math to back it up. Its your life, live it your way. I'm not trying to change or criticize beyond opening a door to a clearer reality.

[@GeorgeGraves]

Darn it Dave! Your last 3-4 videos have been so amazing, that I stop watching half way through, so I can order parts and follow along in the tests you do! You *must* do more of this teaching style stuff! I think you found your pace. Good on ya dude.

[@Milos89kv]

I remember this lesson from university. The point was that current is not only movement of charged particles, but also a change in electric field is also a current. I think that was on forth year. Another argument was that magnetic effect this current has are the same as those of moving charged particles. Can't remember any math or details nowdays, don't really use it in practice. Amazing that, at some point in time, I had some understanding of that stuff.

[@Robstafarian]

Just so you know, one more person on the planet loves you. Great work, mate.

[@pauldow1648]

Never a dull moment here. Thank you for a enthusiastic overview of caps.

[@Alexandreitsme]

That what I like! I wish I could express my self like you do! Keep the teaching I like the eevblog.

[@jenykoo]

I WISH YOU HAVE MORE VIDEOS LIKE THIS EXPLAINING HOW TRANSISTOR WORKS AND STUFF) GREAT CHANNEL!

[@wbeaty]

To stir up more trouble: ignore vacuum capacitors. Instead... in modern ceramic caps about 99.99% is a real electron current in the dielectric. Those electrons in the dielectric can move a bit, but aren't totally free like in metals. Look up ferroelectrics and PZT ceramics. Not "vacuum polarization," but polarized ceramic. So, Maxwell's displacement current actually plays an insignificant role, at least in ceramic caps. That's why their dielectric const is 2,000, or 5,000, or higher.

[@ralfschneider9260]

I love your passion Dave, keep up the good work.

[@johnbrowne3964]

Also what the vid is saying is that current flows into a plate inducing a equivalent magnetic moment which does cross the gap and "knocks" electrons off of the other plate which then are attracted back to the differential voltage source. Currrent here is either a movement of charge (and argueably mass also) or a field of equivalent energy. Here conventional current flow (ie of holes) is interesting, because holes are nothing and can move arbtrairly fast (at least as fast as electricity seems to move) as opposed the electron which are something and therefore slower, but that's a bit off topic.

[@richb313]

Another in a long line of excellent videos Dave. You bring your deep understanding and enthusiasm to your videos and they are informative and entertaining. I have been an E.T. since the early 70's. Having worked with recent tech school graduates in the U.S. I find that they are light on basic DC/AC theory and this leads to me having too supplement their education. These videos are an excellent resource for anyone interested in electronics including recent entries to this field.

[@CarlosArruda77]

Anybody that has tested a capacitor for continuity should have seen that it didn't had any. As you well said, it is basic an opened circuit.

[@jpsousa4]

It's an open circuit to DC and DC only. Any time you try to change the voltage on a capacitor, current flows IN on one lead and OUT on the other, and the currents are equivalent -- current flows through it.

[@pman1902]

jpsousa4 i disagree, when something goes in one end, and something goes out the other end, doesn't mean it went thru. i think this is not the same electron. it are other electrons that already were on the other side to start of with. And just before the same electron that came in first wants to come out the other way, the capacitor refuses and basically says "you, shall not pass!" that's why it doesn't conduct in a DC situation.

[@mmichaeldonavon]

Peter de Man I'd say you are correct!!

[@pufarinu]

Great video Dave! it would be extreamly interesting if you would make a follow-up video regarding the current ripple and voltage ripple of a capacitor as well as losses calculation/measurement of an electrolytic capacitor.

[@DigGil3]

For this is why I loved the «Shock and Awe» show of Jim Al-Khalili! He goes through the thinking of the first people to try understand electricity and how they've evolved the "weird" concepts of it to make sense of how we understand it today.

[@ManoelNunesOSan]

You're totally right Dave, except for one thing: It's not "Asterix", it's "asterisk" (or "asterisc"). "Asterix" is actually Obelix's best friend.

[@405line]

Love the videos. I have always explained capacitors to myself as current flowing onto or into the plates and no further rather than through the capacitor and the fact that ac "passes" as the same energy being returned to source dependent on the "size of the plates"

[@BUNCHofxs]

I always thought it was kind of like filling a bucket with water, when the bucket is empty, water "flows" into it, when it gets full, the water stops "flowing". And all of this happens while no water is flowing on the "other side" of the circuit.

[@misiddiai]

Ok, I do know about the displacement current and all, but still...don't understand how someone could come up with the idea of inserting a capacitor into a circuit and expect it to conduct any current, before Maxwell explained how it works. That just blows my mind.

[@WilliamMcCormickJr]

People misunderstand insulators for sure. A good experiment for you to do is to take a piece of aluminum foil, about two feet long. Lay it on a cement floor it can be a painted cement floor. Put a bag of sand or something similar on the aluminum foil to insure it is contacting the floor over most of its area. You can use a piece of aluminum metal without a sand bag. Attach one lead from a 24 volt DC source to the aluminum foil. You can use two A23 batteries in series. Attach the other lead to a volt meter set to volts, hold the other multi-meter lead in your hand. Then slowly lay down on the floor, watching the meter. As you put one knee on the floor, you will see the meter read voltage. When you put two knees and a hand on the floor you will see it go up in voltage. When you are totally laying on the floor you will probably read around 16-18 volts. Many electrical engineers will tell you that cement could not conduct that kind of low voltage, that it is just impossible. They would be mistaken. Welders know that their 40 volt welding power supply is more then enough to give you a little tingle while you are on your back welding the underside of railings. The ground clamp is attached to railings anchored in the ground, when you change the consumable arc rod, which is powered at all times, you can feel a circuit has been created through your back and the concrete back to the railing. The key is surface area. The same is true with capacitors.

[@MrBrightlight66]

A very good description Dave. A good analogy I once came accross was that of a water pipe with a flexible diaphram inside. The diaphram would stop actual water flow but any variations in flow would still get transmitted from one side of the water pipe to the other. Since water movement is the analogy to electric current, there you have it. Simplistic but easy to understand.

[@Search4TruthReality]

I enjoyed the presentation. Nice review and re-learned stuff I'd forgotten. I work with a few guys who are attempting to build a flying saucer by applying Forbes' monopolor motor wiring to a Tesla-inspired craft designed and built by Otis T. Carr. Carr had labeled plates in his craft's design as capacitor plates; but, his illustrations show these plates as one-piece, folded over an insulator (essentially, a disk on a spindle). The purpose of this so-called capacitor plate isn't completely understood; and, the guys see the plate as a means of invoking rotation, as the disk passed through electromagnets positioned at the periphery / mounted to the internal hull, which is also free to rotate. The ability of them to hold a charge may also be key; as, Carr addresses charged bodies rotating in opposition to each other can cause levitation. Nothing I've yet seen proves this to be true. Carr says he's done it and a man by the name of Ralph Ring claims to have operated a full-sized craft in 1960. More about the wiring of the craft may be seen on my channel. In future videos, I'll keep your channel in-mind for my viewers to get a better understanding of electronics. Again, I enjoyed watching this presentation. Thank you for posting it.

[@davefeda2442]

The concept of dipoles that develop in the dielectric more easily explain the concept of current flow through the cap. Also, it is important to remember that the cap will only have current flow during times of a CHANGE in voltage. Current will flow foe AC, but not DC (since DC does not change). This also explains Xc, the phase shift, and why caps block DC (Xc is infinite when F=0)

[@TonyHammitt]

Say you have a box with 2 sponges filling it, separated by a rubber membrane. You can squirt water in one side for a while and it'll push water out the other side until the pressure you've put on it can't cause any more compression in the other side's sponge. But for a while there, you push water in, and water comes out. It's not the same water molecules, but the current is flowing. You can ease up on the pressure going in and some water will get sucked back into the other side, or you can start sucking water out either way, for a while. Send it alternating directional pressure and that'll propagate. Send it too much pressure one way and no further flow will occur.

[@sbreheny]

I'm being pedantic about it because when most technical people ask "can current flow through a capacitor", they do not mean in the simple sense of "can current flow in one side and out the other", they are usually referring to the question of what is really going on inside, since they know that there is an insulator present between the plates. The question wouldn't even arise if they did not already know that current can flow in one side and current flow out the other.

[@wh459]

Love it. If physics was important on a practical level we may actually get something out of those particle accelerators.

[@curtwuollet2912]

I'm quite happy to use the "apparent" understanding. It works out just fine for all practical purposes. Charge works better as a pile of electrons than a physics problem.