As an electrical enginieer, I learned about the poynting vector in two subjects: Electromagnetism 2 and Transmission Lines. Even though 95% of the time (99,9% if you does not work with antenas) this level of abstraction is not necessary.
I've never heard capacitors described as "breathing energy" before but I think it's a brilliant analogy that would have saved me a lot of confusion when I was trying to understand them.
I always thought of it as a balloon filling up and then popping. Except repeatable, like a bubbler. I was glad to see I wasn't far off the mark, even though I didn't understand the mechanisms involved.
Bellows, for a fireplace. The air in, air out can do two things, it shows how a full capacitor stops a direct current load, and how it smoothes during AC operation.
@@Robert_McGarry_Poems :o That's a mighty fine metaphor you got there. You could compare the AC use case to how a bagpipe is played, but that would annoy the neighbors.
@@Robert_McGarry_Poems look at it like this: energy can be divided in two, power (current, work, amps) and potential (voltage). energy always seeks equilibrium from high potential to low, when it cannot get there it acts capacitively until it arcs over and produces power. the capacitor, much like the earth and the storm, draws in energy from its surrounding sides in order to try and obtain equilibrium. so, what's really happening is, we are storing potential voltage and releasing it as infinite current power the moment the switch closes. in opposition to this, an inductor will store magnetic current and release it as infinite potential voltage when the switch _opens_ - what goes into a capacitor is the same thing coming out of an inductor, and what goes into an inductor is the same thing coming out of a capacitor.
I explain the concept of a resivoir capacitor in a dc power supply as a bucket That's being filled with a sporadic stream of water but has a hole in the bottom where water is steadily flowing out.
Nick, probably the best capacitor explanation I have seen so far. Thank you for that! As an electrical engineer, I was always taught "This is a capacitor, this equation describes how it behaves. That's it." But we were never explained "why" and "how" on a deeper level.
@@ScienceAsylum I myself got to a better feel of understanding a capacitor by considering voltage to be negative-pressure. One side electrons are pushed in by the powersupply but only a few, essentially line is in gridlock. The other side the powersupply keeps pulling the metallic-crystal-"free" electrons off until there is equilibrium in electronforce, making that side positive due to lack-off-electrons. Some current/electrons moves between the plates otherwise the distance between the plates would have no meaning, but because the negative-pressure(voltage) stays at the same value the change in field is not really measurable. Also fun maybe in the future to explain how electron orbitals work inside of metals and how they are different than in molecules, and how metals have "free" electrons on the surface, which can be squeezed together or pulled apart without upsetting the molecular bonds of the material. (like when you keep iterating the same Lego blocks together you will have knobs or gaps sticking out at the surface, some electrons have nothing to do in regard to bonding with another atom.
@@tripplefives1402 I`m looking at it like this, which works in multiple problems i`ve solved in electronics. In a circuit with a battery and a resistor/light. After you throw the switch all the available electrons in the battery`s negative side rush onto the circuit and eventually create full gridlock on the line all the way to the plus side of the battery. (i know the electrons dont actually move all the way around, but the gridlock is the main logic here.) The electrons are then waiting to be processed by the battery which because it`s chemical is slow in passing them from the plus to the negative side, however the battery has a big "plate" so it does a bunch of them (say 1000 or something) in one go. When it processes those 1000 a gap forms on the plate which will be filled by the ones that are waiting in line, after that the next 1000 will fill the gap to move from place 1000-2000 to the first 1000, and so on the gap/bubble travels in the opposite direction to the electron flow. The gap/bubble would be the voltage. That gap/bubble has a collision rate of the next electrons filling in the gap because they are pushed in negative direction by the ones that are waiting behind them. The bigger the gap the higher the voltage, the bigger the speed the electrons get at when the bubble passes and they collide with the ones that already passed the bubble. (think of a waiting line where every car is full throttle but not going any speed because gridlock, the bigger the gap the bigger the impact on the ones in front as the gap passes.) You can imagine what goes on if the gap passes a funnel, like a resistor and on which side of the resistor its getting hot or even failing. Applying this for a capacitor means that the "spark" gap is more created by the electron pull side (+) of the powersupply than the push side, and current does actually flow when charging the cap but that is just the electrons being pulled of the positive plate until the plate is "empty". You need "current" through a cap though otherwise the distance factor would make no sense, but understanding what current is becomes something else completely, just because no current detector (magnetic field meter) can pick up the flow doesn`t necessary mean it doesn`t exist, maybe the draw/pull is so big the electrons are not able to make a field/there is no spread but jump so straight over the gap that nothing can be detected.
I have 25yrs in the HVAC trade. I've spent so much time understanding completely how capacitors really work. They have many uses in motors and circuits. This was a great video, helped visualize the concepts
Well, the purpose of capacitors is pretty simple. It is a local charge source. One of the things that most folks don't realize is when there is a transient voltage and current can bounce around. In HVAC, when you turn on the compressor motor there is a pretty big surge of energy needed to kick things off. So, capacitors are used to store energy right there. Otherwise the voltage could dip and cause problems with various circuits. One of the things that Nick mentioned here but didn't really talk about the application (well he is just a physicist) is that different size capacitors will have a different response time. Remember that charge curve? There is an equivalent discharge curve. So it is sometimes necessary to put different value capacitors on the same circuit to have some discharges that are faster starting and small while others are slower starting but larger.
@@jimsackmanbusinesscoaching1344 The capacitor that is used on many single phase motors such as the motor in an AC compressor is there to create a second phase that gives torque to the rotor to get it spinning. Three phase motors, often found in commercial/industrial equipment, don't need them as the three phase power provides the rotating field for the motor to spin.
@@localverse I know most of it since I've been a subscriber for a long time and loved the series on energy flow in electricity. But I've been really dissatisfied with other explanations this is much better.
@@JohnAudioTech every spool in a ac circuit shifts the current out of phase from the voltage. And you get a current that does no work (exept changing the fields aroud wires but essentially spools). This reactive power isnt detected by your power meter because it flows back to the power station but it makes a a bigger current that can be detected by circuit breakers and heats up the conductors. Your energy provider doesn't want to pay for that energy thats used to heat up cabels so here (germany) they mandated the maximum the voltage and current are allowed to be out of phase. A capacitors shifts the voltage behind the current and gets them closer in phase so you reduce the reactive power.
I use variable air gapped capacitors for shortwave listening. They are absolute works of art! Beautiful things! I love watching the plates slide between each other as you tune them to resonance.
@@Robert_McGarry_Poems Look at "Variable Capacitors" on Wikipedia. There you'll see images of air gapped caps used in impedance matching to tune antennas. I use them for shortwave (HF) frequencies. That should give you enough keywords to find some beautiful variable air gapped caps. 😃
Thank you for drawing out the Poynting vectors on this one. I know it's ridiculous to get into all the minutia about the physics, but that made your previous video about energy flow make a little bit more sense.
@@ScienceAsylum It looks great, and it's a nice companion to the ElectroBOOM video you referred to as well, as he in turn referred to your older video, to "debunk" Veritasium's recent video about it. But yeah during this video i was wondering if you did your own graphics, as the logo 'watermark' on the capacitor were definitely made for you, just wasn't sure if they were made by you, but that is cool to know. Hope you get your 1 million subs in 2022 :)
Great explanation! I was going to ask Veritasium to make a follow up video about the circuit energy flow video...but no need now. Your ability to explain complex concepts in a simple way with a pinch of humor is truly amazing. Really appreciate it. Plus you manage to do it without any click bait ;)
I have to say I've learned more about electric fields from your channel than anywhere else. Very interesting perspective and way of conveying information. And thank you for toning down the wild screaming and side stuff. I like the tone of this video a lot. Good work!
When I was a teenager I had an air-gap variable capacitor to tune a crystal set radio receiver. It also had a hand-wound coil on a cardboard tube as the inductor. The antenna was a wire strung from my bedroom window to a post down the garden. That led to a lifetime career in electronics.
This is revolutionary - please keep going. I'm old school - classically trained but understand where you are going here. The jump start you can give our new experimenters will be profound.
Yes. I've always been interested in electronics, but it DEEPLY bothered me to NO END that no-one would ever explain what's inside micro-electronics and how EXACTLY they work. I like to tinker and learn how things are made and interact to be able to understand deeply how they work, but with things like this, it was just expected to accept that they were a black box of magic and they could be used for these specific things or act in this specific way, but not how. Like transistors, how tf do you expect it to make sense to someone and for them to fully understand their capabilities and weaknesses if they don't/can't understand ho exactly they work. I still struggle with this, have you done more, if so, where can I find them?
@@OverlordIcy Yes, I have a few suggestions for you: Veritasium, The Science Asylum (this channels PlayList for Electricity), Altium Live with Rick Hartley or Eric Bogatin. What you will find is that Circuit Board designers PCB designers know the Poynting Vector, How Electrodynamics is what electricity is. Search for Transmission Lines and Poynting Vector - that is a good start, the videos by Rick Hartley are easier to follow too. Basically the Energy in any Circuit is from the Electric and Magnetic Fields, the Voltage and Current are factors but they do not carry the energy - it's All about the Fields. I'm still a hobbyist too and following these suggestions you will begin to unfold what Electrical Energy is. Good Luck
@@OverlordIcy As for specific components - you can do a deep dive. Most Microprocessors are logic gates, logic gates are made from transistors, transistors are make from the process of mixing Silicon with other materials to create Negative and Positive charges within the molecules - Negative charge is an abundance of Electrons, and a Positive charge is a lack of Electrons inside a material.
Hey you're doing great man thank you for consistently blowing my mind. We had our first child this year and want to homeschool our kids. This year your channel changed the way I view education and learning. Going to be a long time before even our first kiddo touches anything you've taught me but I won't forget. She'll be watching your videos and learning alongside me sometime soon so please don't stop. God bless you and your wife. Happy new year. Keep doing it man!
That animation at 11:20 is very good representation to clear up the misconception, that the energy does NOT leave the neighborhood of the wire. It is outside and around the wire, but still goes along the wire, following its direction. It’s like if you replace the real wire with a much thicker imaginary wire with no definitive edge, which goes in the same direction.
If only teachers at school/college would be as Lucid as Nick... things would be very different I'm sure! Great video as always. Thanks for the content!
You can obtain content enough from the textbook plus the great teachers like Nick on RUclips, I wish it had been around when I was at school. Obtain the info, complete the exam. Simple.
7:50 - I was an electronic technician in the Navy, I was then an electrician for 10 years, I then went on to get bachelor's and master's degrees in electrical engineering. Long story short, I have a lot of experience with electrical teaching techniques. Anyway, I have never heard this diaphragm analogy for a capacitor. I like it.
10:38 Oh right! So _that's_ why doping a semiconductor makes it a better conductor -- it doesn't give any more energy to the charge carriers, just means _more_ charge carriers are free to move around. I'm currently taking an EE class on semiconductor physics and we're finally getting to the parts that relate to electrodynamics (as opposed to the lower level stuff that's all quantum mechanics and statistical chemistry) so that's what came to mind rewatching this video. It's amazing how _connected_ everything is in physics.
I really appreciate this deeper dive into capacitors. When I first started studying electronics, capacitors were always where I got tripped up. This was very helpful.
When I was an engineering student in college, we had to take Physics I and Physics II For Engineers, so we got both the physics and the engineering of capacitors. Fun stuff.
I did a few years of maintenance and HVAC work and I always wondered what exactly is going on inside a capacitor! I remember asking my boss about it and it kind of went over my head so I always just figured they were kinda like those huge rechargeable portable batteries you can use to charge your phone. This really broke it down and I can say I get it much more now. Really cool!
@@JabranImran maybe. Veratasium make a specific assertion. Uses the word lies. Says energy will arrive in speed of light pretty much regardless of the wiring diagram. Etc...
@@playgroundchooser hmm. Unsure who is trolling whom here. I'm of the opinion Derrick is trying to assert science without experiment. Might even call it trolling, but I'd avoid that word.
@@BenjaminGatti Oh, no no. I mean that Nick warned Derrick of trolls in his comments, not you my man. You bring up a good question. I think Nick is more about the physics (the math itself) behind the problem.
Capacitors are just like synapses between neurons. Jumping "variable current" from one edge to other edge of the capacitors periodically as so called "the resonance" or ""oscillation"". It is sensitive just to the CHANGE as much as its RANGE(capacity, Farad). It is also something like bedroom lamp which shines while movement continues back and forth. When "back-forth" voltage change is extinguished, then it will be sleep time for the lamp...
I am an audio engineer, and we use these things called transformers all the time... they block DC, but allow AC to flow... therefore allowing our digitized sound to flow, but blocking the DC used in many of our devices. A transformer is a capacitor, but instead of it just being nothing in the gap, its a separate wire entirely that essentially carries the magnetic field of one cord and then imprints it on another. This happens in your microphone on your phone, and the speaker on your phone! Not to mention likely several other places on the phone.
Love to see SA referring Electroboom in the video. I love them both. One is a brilliant theoretical physicist and the other a brilliant Electrical engineer. My knowledge about electricity (both AC and DC) has increased a lot by watching videos like this.
I am intimately aware of them due to condenser microphones, I looovvveeee the science of capacitance I love your videos and am stoked to see you doing one on this concept!
I am a lifelong retired electronics & software engineer, and all this physics BLOWS MY MIND! Pointing vectors AGAIN! My head CANNOT TAKE IT!!!!!!!!!!!!! I use maths a lots sometimes for circuits, but you physics guys are on a different level!
Wow... that was a golden 10 minutes lesson. Learned more now than with prep courses into university and a whole year of electromagnetism in a geology major! Thanks dude!
It's just been since last semester that I took a course in introduction to physics 2 where we learnt all around electricity, magnetism, circuit components and it's still so amazing to see just how weird and magical energy behaves
Hey Nick, I loved this video! As an Electrical Engineer, I was also kept fascinated by the way in which this beautiful thing works. All my imaginations and understandings about capacitor were proved right here! Ahh! I feel so happy right now! And that capacitor energy flow is really cool. Thanks a lot Nick! ❤️
That explains a lot, capacitors always seemed like an exception that showed that the rules taught in electronics in school were just a vauge simplification. Thank you!
Saying "superconductors have zero resistance" is easier and sounds more confident than saying "their resistance is below our ability to measure." It's laziness.
@@ScienceAsylum oh wow I never noticed! I just looked at an experiment where they use very low currents to avoid heating the sample. How would it heat up if there was truly zero resistance ;) I'm sure it's much more complicated though, with all the different types and stuff...
@@kylebowles9820 Superconductors have a maximum current above which they cease to superconduct, so yeah the current does need to be controlled if you want to actually have a superconductor
@@triffid0hunter i think the point is that per the conservation of energy, if current generated heat, any amount, there must be resistance. If the resistance was truly zero, heat could not be generated by the current.
Thanks for teaching me about the Poynting Vector for the third time....I forget once every score years. Your stuff is helping out. I learned electronics theory in a Vocational Radio & TV Repair class. The Instructor only briefly mentioned the EM Field and the Poynting Vector, but didn't get serious about it or quiz us on it. In Electromagnetism Physics class, I got the whole gory treatment.... but never really blended it with my electronic circuit theory memories. 40 years later, you helped finish the job.
You are the best teacher ever! So many times now have you managed to teach me something new about something I already thought I understood, and in so doing made the knowledge intuitive instead of memorized. You rock!
Mind. Blown. I was looking through a powerpoint that louis rossmann made that gave a rough overview of electrical engineering (just enough to do electronics repairs) where he said that capacitors block DC but allow AC to pass. It seemed so counterintuitive that I was certain he made a typo. I though for sure it should be the other way around. But this video really shines a light on why it works the way it does! Thank you for all your hard work making these videos! 💯👍
@@whuzzzup they both shift current and voltage away from each other in a pepetual transiant state (AC) a capacitor shifts tha voltage behind the current and an inductor shifts the current behind the voltage.
Dear Nick, there is still a simplification in here: In 05:20ff it's suggested that all the wire and both plates of the capacitor are completely neutral as long as the switch is open. This cannot be true since the battery is already connected with the wire at both sides, meaning that the later positive plate must already be slightly positive at the beginning to be at the same potential as the plus pole. What's the minus side then? It must be the near (seen from the battery) side of the open switch in a way that this and the later positive capacitor plate act as a capacitor of extremely low capacity which means the same voltage at an extremely low charge. The rest of the wire, including the later negative plate of the capacitor, act as a kind of dielectric since they get a slight charge gradient via influence.
Best depiction of real science I have ever seen in all the youtube science channels This is what ALL PHYSICS is all about 4:26 It's not fun like laughing and smiling or watching a 5 minute video and saying "Now I understand" It is fun in this way 4:53
One of my great embarrassments is that i never learned electronics along the way. Not without lack of trying, but most of the resources I've had over the years gloss over so much in a don't-worry-your-pretty-little-head-about-it way. I crave a deeper understanding, and your videos have been one of the best resources I've run into to gain that understanding. Thank you, Nick. I hope you do more of these-and any time you want to create a dedicated electronics course, I'm totally there. :)
How long did it actually take you to derive that expression for V_c at 4:53? I'm glad you showed the actual math even if you sped it up so viewers didn't have to watch, because I paused it abd worked through your algebra, which reminded me how transient analysis actually works. It also made me realize what I don't think really hit me when I learned it in class a couple years ago: its really just applying boundary conditions to a D.E. general solution to get the specific solution. So many E&M problems come down that process.
@@localverse Differential equation(s). To briefly summarize what I was talking about, a differential equation is simply an equation involving derivatives (if you haven't had calculus, a derivative is a function giving the rate of change of another function; e.g. the derivative of f(x)=2x+5 is f'(x)=2). Since rate of change is such a broad concept, D.E.'s show up all over the place in physics (and other sciences too). In regards to capacitors specifically, the equation that describes the charging of a capacitor is the solution to a D.E. The actual equation, for a circuit with just a resistor and capacitor (which is the type of circuit Nick showed in the video) is I(t)=(Vₛ/R)e^(-t/RC), where Vₛ is the voltage of the power source. It essentially says that the current will decrease exponentially with time, starting with a value of Vₛ/R and decreasing at a rate depending on RC.
@@Lucky10279 as someone who tries to follow physics but is rusty on the math (2 decades since I took calculus), this was probably the single most useful / impactful youtube comment I've come across. Now I have to go back and re watch some of those Sean Carroll explanations. Thanks!!!
"The charge must flow!" - 😂I almost didn't get it - classic!! Thanks for another great video - wish I'd had a science teacher like you at school - what a difference that would have made! Could say the same for my theoretical physics courses at uni sometimes too! :)
@@whatelseison8970 In case you’re actually asking for an explanation: It’s a reference to Frank Herbert’s sci-fi classic “Dune” and the phrase “The spice must flow”.
@@germansnowman fun fact, "the spice must flow" is a phrase used in movies and mini series based on Frank Herbert's work, but he didn't use the phrase in the original novels.
Best explanation ever, for two reasons. First the modelling makes a difficult concept much easier to visualise and understand. Secondly is the nitty gritty details for those who want to delve a bit further.
It definitely IS a beautiful abstraction. The energy flowing from the battery to the capacitor not by electrons being pushed on one plate and removed from the other (that is only charge being moved) but through the EMfield from all around is still a mindshift for me. Waiting for the coils now :-) .
Actually, the only physical thing is the movement of charge (there are separate components for the velocity and acceleration which behave very differently). The magnetic field is just something we measure as a result of moving charge. And the energy is just a mathematical abstraction for bookkeeping. At the fundamental level there are just moving charges influencing each other with a time delay due to the finite speed of light. We describe that by convenient notions of electric and magnetic fields and the even more abstract notion of energy. The electric field is the part we would measure if the charges weren't moving. The magnetic field is essentially just the adjustment we need to make because the charge moved from the location where we would have otherwise measured it to be and that "information" took time to reach us. Thinking of energy as some kind of substance flowing into a gap is also not really that helpful. It's not really a physical thing that moves. The actual physical things that move are the charges. The rest is just something we either measure or something we use mathematically to do bookkeeping. Of course the whole thing gets really wild when we introduce quantum mechanics, where radiation (one of the two components I discussed above) is considered. We know it is quantized and we have absolutely zero idea what a measurement actually is physically in this context. Anyone who tells you we do is just making stuff up. The measurement problem is a major unsolved problem in physics. But at a deep fundamental level we need to distinguish between what is physical, what is measured and what is bookkeeping for convenience but totally nonphysical and non-measurable. For example, set up a permanent magnet in a static electric field. The Poynting vector then says there is energy flux in some direction. But good luck measuring it. It does not correspond to something physically measurable. (Mathematically it is intrinsic angular momentum, i.e. angular momentum when you are not having angular momentum. You can demonstrate it must have been there by doing certain tabletop experiments, but ultimately it is just something that we infer is there for bookkeeping purposes. There's not something actually spinning there in the gap between the magnetic poles and the charged plates!)
As an electrician, I have to say your videos explain the actual physics of electrical circuits in much more realistic detail than I ever learned in school. Thanks for your explanations and great work as always.
I have a pretty cool story about Capacitors from when I was in University. I was in a circuits lab where we were measuring electric waves with an oscilloscope at different frequencies but we kept getting this 6 GHz signal mixed into our wave, for low frequencies we could basically ignore it, but by the time we were measuring a 1 GHz one (the highest frequency we were working with) it became impossible to ignore while getting anything resembling good data (it probably was messing with our accuracy before that I just don't remember that well). Anyway, we asked the TA that was running the lab, but nothing he suggested worked, but finally we asked the Lab Tech who looked at it and put in a capacitor (or 2, I can't remember the details) in the circuit and the 6 GHz signal vanished, because a capacitor acts as a short for high frequency signals so the high one just drained away (or at least that's how they described it) and we could finish the experiment.
I always think of a capacitor as a DC blocker, but one that allows more current flow as frequency increases, depending on the resistances and impedances in the circuit. I'm old school!
A teacher of teachers. Very precise, concise, and all around just nice. Keep up the good fun and happy new years! Oh yeah, capacitors really are super cool! You know what has a diaphragm? living things, for their lungs. It seems that our own circulatory system can be used analogously to an electrical circuit, hmm? Heart, as the battery; capacitors, for the lungs. I wonder what other analogous electronic parts fit?... Also, there's about to be a revolutionary new capacitor coming out soon that I hear will replace LI batteries.
This video is simply BEAUTIFUL! I'm familiar with almost all of the terms you've used in this video, Displacement current, Poynting vector etc. But it's only know that I've actually understand what happens. Thank you so much for this
When we deal with grounding of various parts of Space Flight batteries we have to qualify parts in milliohms. Basically, our connections have to be at wire resistance levels.
If this dude took psychedelics while *scientifically and mathematically* analyzing whats happening in neither a spiritual nor a mocking manner we might be lookin at the next Nikola Tesla for real. Over the years, much of my understanding of math and quantum mechanics has come from analyzing my psychedelic experiences and my lucid dreams. Ive been a math and science nerd growing up and i really looked at everything like a math equation or theorem to be solved. I NEED to know "why" for everything. So simply having my brain do unimaginable things was not enough. *Why* is this happening?? This channel has coalesced alot of my understanding into pure knowledge since ive found this channel a month ago. Man so many of my experiences over the years make so much more sense now its freakin powerful and weird AF. Literally kno other channel ive seen has done this youre like, a whole thing kudos
I'm always in awe of the people that figured these things out when everyone else thought it was magic... I can't even understand it when it's thoroughly and reasonably explained! I'm pretty sure capacitors are magic... :D
Can you read my mind? Cause I was watching your video about how energy actually flows in a circuit on 28 of December, and today you've done this one that further explains how things works . I love it 😍
Great video - a few things that would be worth mentioning (for the you know, practical folks...) First, is that a dielectric will increase the capacitance, by the relative permittivity. Second, the charge on the capacitor is proportional to both the Capacitance and Voltage (Q=CV). Finally, the energy goes as the square of the voltage (E=1/2 CV^2). Many thanks once again!
Although my knowledge of quantum mechanics is limited, I appreciate this video as a metal fabricator. If a capacitor in my welder goes bad, the welder will still work but with reduced performance...way reduced.
We learned a bit about these when I was in welding school, in particular that you needed to be aware of them if you were doing maintenance. Cool to learn a bit more!
I'm a welder, I've always been curious about the physics involved with arc welding, we usually run electrode positive DC circuits with welding rod, and the heat tends to focus in the base metal, what is actually happening in the arc?
With SMAW (Stick welding) the electrode positive polarity makes the rod actually get consumed, which drives the arc characteristics and such. It's the opposite with GTAW (tig welding) where there is not a consumable electrode. For tig welding, it's DCEN (electrode negative) and that makes all of the heat go into the base metal.
I’ll explain this in electron current flow, not traditional current flow. Stick and MIG welding are DCEP (direct current electrode positive), meaning the ground is hooked up to the base metal. TIG welding is DCEN (direct current electrode negative) meaning the positive is hooked up to the base metal (except on aluminum or magnesium, where the cleaning action/heat management of AC alternating current is needed). In stick welding, you are creating a net negative charge on the base metal, hooked from the - cable on the voltage source. This happens because it is more electron charge dense in relation to protons. The + cable on the voltage source is hooked to the welding stick, and creates a net positive charge, because electrons are pulling them from the stick and into the voltage source, so the stick is less electron dense in relation to protons. When the positively charged stick touches the negatively charged base metal, electrons are violently pulled from the base metal into the stick. This enormous amount of heat creates the arc that allows the stick to be fused with the base metal. It doesn’t matter if the electrons are being pulled from the base to electrode, or vice versa. Because in TIG welding the electrons are ripped from the tungsten electrode to the base metal, which is the opposite of MIG/Stick. And in AC welding, the electrons are constantly being pushed/pulled each way- like TIG polarity, then MIG polarity, 120 times per second. The heat and ionization is the important part. In the presence of oxygen, it wants to pull electrons from the metal and give it to the oxygen, and over-oxidize the material. That’s why you use more inert gasses, so electrons can’t be stripped and over-oxidize your material. Inert gasses do not pull electrons from your material, making a smooth transition of electrons from stick to base, and thus don’t oxidize them. Inert gasses do not have available electron-empty spaces in their outer orbitals to steal them from metals. Different Inert gasses are chosen for specific metals too, because electron properties are different for both.
@@rebeuhsin6410 Stick welding uses flux on the outside of the stick, that coats and vaporizes as an (inert) gas over the welds. It serves the same function as inert gases passed through a nozzle on MIG welding. TIG uses a non-consumable tungsten tip to create the arc, and a metal consumable rod is used while fed in.
The air gap between the electrode and the metal plate is a "resistor" an invisible one...5000volts per centimeter and lower at like 500 volts per mm... That gets multiplied by the amperes... Equals wattage.,. You control the gap with your hands.. Your actually controlling the resistance bigger gap more resistance less amperes... Closer narrow gap is less resistance more amperes.... More electrons more heat . More melting
When I first learned electronics at college 35 years ago, understanding actually how capacitors worked... well, I simply didn't. I just accepted that they blocked DC but 'somehow' passed AC with the plates charging and shit, lol. Even diode and transistor theory seemed easy by comparison. I think capacitors, along with their varied uses, are a wonder within electronics... no, they're the unsung heroes!
I often use the water analogy for trying to explain voltage and current... But I had never seen your example using the rubber dam inside the capacitor ! That's pretty good ! Next, I suppose you will be talking about the dielectric constant. Or not. 😍😀
I studied capacitors in this way on my engineering career, we had a subject that studied almost every component of a circuit but in a physic/theoric way. Was really interesting.
Now that WOULD be a good metaphor for an inductor, since it resists changes in current, kinda giving some metaphoric 'inertia' to the current in circuit
Caps are much more like springs or elastic bands. In fact, there's an old timey unit for inverse capacitance called "elastance". It's a better analogy when you think about the polarity of the voltage as you force charge onto the the plates - that is, it comes back out the same way it went in. On the other hand a flywheel only stores up energy as you accelerate it and releases it when you try to slow it down but the wheel only has to go in one direction through those changes. They also behave similarly in that you can charge a cap just like you can wind up a spring and they can both just kinda sit there charged up until you get the energy out because it's being stored as _potential_ energy. In an inductor the energy is only stored as long as current flows just like a flywheel needs to be spinning to store it's energy. In some sense they both store _kinetic_ energy. And because there's a natural duality between potential energy and kinetic energy a cap connected to a coil will hand their energy back and forth at a particular frequency the same way a flywheel hung off the end of an elastic will spin back and forth.
@@localverse Yes. That is what an inductor does. It reacts to an attempt to change the current in it, and applies a voltage to the rest of the circuit to oppose this change. A capacitor would be analogous to elasticity in the mechanical world, where energy is stored in the form of potential energy by virtue of position/configuration. An inductor is analogous to inertia, where energy is stored by virtue of motion. Resistance is analogous to viscous friction, where energy leaves the domain of reversible processes and is converted into thermal energy. Like resistance requires a voltage drop across it to sustain a current, a viscous friction requires a force to sustain a constant velocity. For viscous forces, it is proportional to velocity. For other regimes of fluid resistance, it is a lot more complicated and extremely non-linear.
a guy in one of my electronics classes ended up with a mark on his face when he hooked up his electrolytic capacitor backwards and it got real shiny real quick... instructor took the opportunity to point out 2 things: 1. make sure you're hooking up your electrolytic capacitors correctly. 2. this is why we wear safety goggles.
Thanks, Nick, for your improved Poynting vector graphic which now clearly shows that the energy flow density is greatest nearest the conductor and then drops off further away from the conductor (specifically the Poynting vector magnitude is inversely proportional to the biquadrate of the distance [square of the square, or 4th power] away from the conductor). This means that almost all of the energy flows along the surface of the conductor.
Love the ending: "That means energy flowing inside fields is an abstraction inside of another abstraction. But it's really beautiful to look at, isn't it?"
Pretty much. Physics is _full_ of abstractions on top of abstractions. Computer science and software engineering have got physics beat in regards to the sheer _layers_ of abstraction they use though.
I just finished understanding Displacement current and Maxwell's equation from my physics book and you dropped this video this made them more clear to understand. Thanks Nick!
I get it that theoretical physicicists eschew practical matters 🤣. In practice though, the internal resistance of the battery is more significant than the resistance of the connecting wires-the latter can usually be ignored. So when analyzing or designing circuits, we engineers model voltage sources with an explicit series resistance (Thévenin's theorem). Coincidentally, for the circuit that you were analyzing, it gives the same result that you got by assuming that the wires have a significant resistance. Lucky you!
Great video Nick, from the El.Eng. perspective I would only add: the main application of capacitors is to build circuits which can filter frequencies, i.e. through capacitors we can select and isolate frequency ranges in the perturbations of the electrical field. That has applications in basically any useful electronic device.
What happens right around the wires? The energy is flowing along the fields around them towards the light bulb, capacitor, etc. In some places, it looks like it's flowing away from the wires (e.g. near the battery). But if the wires are experiencing resistive heating, then they must be pulling energy from the fields. Does that go into the wires from the outside? In which case is there some particular distance from the wire where energy is not flowing at all? Or some kind of "event horizon" where energy will either end up going into the wire or into the device?
*"But if the wires are experiencing resistive heating, then they must be pulling energy from the fields."* Yes, while most of the energy goes into the light bulb, some of it does go into the wires (from outside but is immediately turned into heat). The exact direction of the Poynting vector depends on resistance. The Poynting vector near a conductive wire is _ever so slightly_ slanted toward the wire.
This is why we have grouping factors and balance runs with return paths. It’s extra interesting when you think what is actually happening, it’s so counter intuitive!
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Poggers
As an electrical enginieer, I learned about the poynting vector in two subjects: Electromagnetism 2 and Transmission Lines. Even though 95% of the time (99,9% if you does not work with antenas) this level of abstraction is not necessary.
best science channel on youtube , why didnt varatasium credit you for stealing your video idea tho ?
@@borgholable He _did_ credit me, just not verbally in the video. I'm listed as a reference in the video description.
Took me a while to remember who Fabulous were but damn glad they're still around :D
Used their app a few many years ago
I've never heard capacitors described as "breathing energy" before but I think it's a brilliant analogy that would have saved me a lot of confusion when I was trying to understand them.
I always thought of it as a balloon filling up and then popping. Except repeatable, like a bubbler. I was glad to see I wasn't far off the mark, even though I didn't understand the mechanisms involved.
Bellows, for a fireplace. The air in, air out can do two things, it shows how a full capacitor stops a direct current load, and how it smoothes during AC operation.
@@Robert_McGarry_Poems :o That's a mighty fine metaphor you got there. You could compare the AC use case to how a bagpipe is played, but that would annoy the neighbors.
@@Robert_McGarry_Poems look at it like this: energy can be divided in two, power (current, work, amps) and potential (voltage). energy always seeks equilibrium from high potential to low, when it cannot get there it acts capacitively until it arcs over and produces power. the capacitor, much like the earth and the storm, draws in energy from its surrounding sides in order to try and obtain equilibrium. so, what's really happening is, we are storing potential voltage and releasing it as infinite current power the moment the switch closes. in opposition to this, an inductor will store magnetic current and release it as infinite potential voltage when the switch _opens_ - what goes into a capacitor is the same thing coming out of an inductor, and what goes into an inductor is the same thing coming out of a capacitor.
I explain the concept of a resivoir capacitor in a dc power supply as a bucket That's being filled with a sporadic stream of water but has a hole in the bottom where water is steadily flowing out.
Nick, probably the best capacitor explanation I have seen so far. Thank you for that! As an electrical engineer, I was always taught "This is a capacitor, this equation describes how it behaves. That's it." But we were never explained "why" and "how" on a deeper level.
Thanks! I'm glad you appreciate it 🤓
The 'why' and 'how' were never addressed when I studied these subjects, such a shame
@@ScienceAsylum I myself got to a better feel of understanding a capacitor by considering voltage to be negative-pressure.
One side electrons are pushed in by the powersupply but only a few, essentially line is in gridlock. The other side the powersupply keeps pulling the metallic-crystal-"free" electrons off until there is equilibrium in electronforce, making that side positive due to lack-off-electrons.
Some current/electrons moves between the plates otherwise the distance between the plates would have no meaning, but because the negative-pressure(voltage) stays at the same value the change in field is not really measurable.
Also fun maybe in the future to explain how electron orbitals work inside of metals and how they are different than in molecules, and how metals have "free" electrons on the surface, which can be squeezed together or pulled apart without upsetting the molecular bonds of the material. (like when you keep iterating the same Lego blocks together you will have knobs or gaps sticking out at the surface, some electrons have nothing to do in regard to bonding with another atom.
@@tripplefives1402 I`m looking at it like this, which works in multiple problems i`ve solved in electronics.
In a circuit with a battery and a resistor/light.
After you throw the switch all the available electrons in the battery`s negative side rush onto the circuit and eventually create full gridlock on the line all the way to the plus side of the battery. (i know the electrons dont actually move all the way around, but the gridlock is the main logic here.)
The electrons are then waiting to be processed by the battery which because it`s chemical is slow in passing them from the plus to the negative side, however the battery has a big "plate" so it does a bunch of them (say 1000 or something) in one go.
When it processes those 1000 a gap forms on the plate which will be filled by the ones that are waiting in line, after that the next 1000 will fill the gap to move from place 1000-2000 to the first 1000, and so on the gap/bubble travels in the opposite direction to the electron flow.
The gap/bubble would be the voltage.
That gap/bubble has a collision rate of the next electrons filling in the gap because they are pushed in negative direction by the ones that are waiting behind them.
The bigger the gap the higher the voltage, the bigger the speed the electrons get at when the bubble passes and they collide with the ones that already passed the bubble. (think of a waiting line where every car is full throttle but not going any speed because gridlock, the bigger the gap the bigger the impact on the ones in front as the gap passes.)
You can imagine what goes on if the gap passes a funnel, like a resistor and on which side of the resistor its getting hot or even failing.
Applying this for a capacitor means that the "spark" gap is more created by the electron pull side (+) of the powersupply than the push side, and current does actually flow when charging the cap but that is just the electrons being pulled of the positive plate until the plate is "empty".
You need "current" through a cap though otherwise the distance factor would make no sense, but understanding what current is becomes something else completely, just because no current detector (magnetic field meter) can pick up the flow doesn`t necessary mean it doesn`t exist, maybe the draw/pull is so big the electrons are not able to make a field/there is no spread but jump so straight over the gap that nothing can be detected.
"But we were never explained why and how on a deeper level."
Basically the entire history of my school years.
I have 25yrs in the HVAC trade. I've spent so much time understanding completely how capacitors really work. They have many uses in motors and circuits. This was a great video, helped visualize the concepts
What surprised you the most from the video? Did you already know the part that electrical engineering classes usually don't teach?
Well, the purpose of capacitors is pretty simple. It is a local charge source. One of the things that most folks don't realize is when there is a transient voltage and current can bounce around. In HVAC, when you turn on the compressor motor there is a pretty big surge of energy needed to kick things off. So, capacitors are used to store energy right there. Otherwise the voltage could dip and cause problems with various circuits. One of the things that Nick mentioned here but didn't really talk about the application (well he is just a physicist) is that different size capacitors will have a different response time. Remember that charge curve? There is an equivalent discharge curve. So it is sometimes necessary to put different value capacitors on the same circuit to have some discharges that are faster starting and small while others are slower starting but larger.
@@jimsackmanbusinesscoaching1344 The capacitor that is used on many single phase motors such as the motor in an AC compressor is there to create a second phase that gives torque to the rotor to get it spinning. Three phase motors, often found in commercial/industrial equipment, don't need them as the three phase power provides the rotating field for the motor to spin.
@@localverse I know most of it since I've been a subscriber for a long time and loved the series on energy flow in electricity. But I've been really dissatisfied with other explanations this is much better.
@@JohnAudioTech every spool in a ac circuit shifts the current out of phase from the voltage. And you get a current that does no work (exept changing the fields aroud wires but essentially spools). This reactive power isnt detected by your power meter because it flows back to the power station but it makes a a bigger current that can be detected by circuit breakers and heats up the conductors. Your energy provider doesn't want to pay for that energy thats used to heat up cabels so here (germany) they mandated the maximum the voltage and current are allowed to be out of phase. A capacitors shifts the voltage behind the current and gets them closer in phase so you reduce the reactive power.
I use variable air gapped capacitors for shortwave listening. They are absolute works of art! Beautiful things! I love watching the plates slide between each other as you tune them to resonance.
I wonder if what I was thinking about, the rather large air gapped capacitors, had anything to do with early radio? 🤔 I can't remember...😞
@@Robert_McGarry_Poems Look at "Variable Capacitors" on Wikipedia. There you'll see images of air gapped caps used in impedance matching to tune antennas. I use them for shortwave (HF) frequencies.
That should give you enough keywords to find some beautiful variable air gapped caps. 😃
@@Aengus42 Thanks that totally helped. Yeah, it's been so long since I did that initial research into the subject.
Weren't those old variable caps called condensers?
@@mikelastname Old timers would call them tuning condensers. It's just an old fashioned name for capacitors.
Thank you for drawing out the Poynting vectors on this one. I know it's ridiculous to get into all the minutia about the physics, but that made your previous video about energy flow make a little bit more sense.
I didn't have the animation skills to do it last time. Now that I have those skills, I felt like this needed a revisit.
@@ScienceAsylum What software do you use and how did you learn it?
@@ScienceAsylum It looks great, and it's a nice companion to the ElectroBOOM video you referred to as well, as he in turn referred to your older video, to "debunk" Veritasium's recent video about it.
But yeah during this video i was wondering if you did your own graphics, as the logo 'watermark' on the capacitor were definitely made for you, just wasn't sure if they were made by you, but that is cool to know.
Hope you get your 1 million subs in 2022 :)
Thanks for Pointing it out 😅
@RUclips Official because there is no nobel prize for teaching great things but for fundamental research results...?!
Great explanation!
I was going to ask Veritasium to make a follow up video about the circuit energy flow video...but no need now. Your ability to explain complex concepts in a simple way with a pinch of humor is truly amazing. Really appreciate it. Plus you manage to do it without any click bait ;)
Chintan
Yeah, tbh looking at this video I'm _really _*_really_* wondering why it was so controversial.
I have to say I've learned more about electric fields from your channel than anywhere else. Very interesting perspective and way of conveying information. And thank you for toning down the wild screaming and side stuff. I like the tone of this video a lot. Good work!
I have to say I support every minute Nathan Rich sits in front of someone else's content while he can't shill for the CCP.
Check out " The Big Misconception About Electricity" video.
When I was a teenager I had an air-gap variable capacitor to tune a crystal set radio receiver. It also had a hand-wound coil on a cardboard tube as the inductor. The antenna was a wire strung from my bedroom window to a post down the garden. That led to a lifetime career in electronics.
This is revolutionary - please keep going. I'm old school - classically trained but understand where you are going here. The jump start you can give our new experimenters will be profound.
Yes. I've always been interested in electronics, but it DEEPLY bothered me to NO END that no-one would ever explain what's inside micro-electronics and how EXACTLY they work. I like to tinker and learn how things are made and interact to be able to understand deeply how they work, but with things like this, it was just expected to accept that they were a black box of magic and they could be used for these specific things or act in this specific way, but not how. Like transistors, how tf do you expect it to make sense to someone and for them to fully understand their capabilities and weaknesses if they don't/can't understand ho exactly they work. I still struggle with this, have you done more, if so, where can I find them?
@@OverlordIcy Yes, I have a few suggestions for you: Veritasium, The Science Asylum (this channels PlayList for Electricity), Altium Live with Rick Hartley or Eric Bogatin. What you will find is that Circuit Board designers PCB designers know the Poynting Vector, How Electrodynamics is what electricity is. Search for Transmission Lines and Poynting Vector - that is a good start, the videos by Rick Hartley are easier to follow too. Basically the Energy in any Circuit is from the Electric and Magnetic Fields, the Voltage and Current are factors but they do not carry the energy - it's All about the Fields. I'm still a hobbyist too and following these suggestions you will begin to unfold what Electrical Energy is. Good Luck
@@OverlordIcy As for specific components - you can do a deep dive. Most Microprocessors are logic gates, logic gates are made from transistors, transistors are make from the process of mixing Silicon with other materials to create Negative and Positive charges within the molecules - Negative charge is an abundance of Electrons, and a Positive charge is a lack of Electrons inside a material.
"I theoretical physicisttt" almost cost a very painful 'soda-out-nose' incident I laughed so hard. Please keep doing these outstanding videos!
So you can keep spitting soda out of your nose?
Hey you're doing great man thank you for consistently blowing my mind.
We had our first child this year and want to homeschool our kids. This year your channel changed the way I view education and learning. Going to be a long time before even our first kiddo touches anything you've taught me but I won't forget. She'll be watching your videos and learning alongside me sometime soon so please don't stop.
God bless you and your wife. Happy new year. Keep doing it man!
That animation at 11:20 is very good representation to clear up the misconception, that the energy does NOT leave the neighborhood of the wire. It is outside and around the wire, but still goes along the wire, following its direction.
It’s like if you replace the real wire with a much thicker imaginary wire with no definitive edge, which goes in the same direction.
Yup, 'cause magnetic field strength drops dramatically as you go far and far away from the wire 👍
If only teachers at school/college would be as Lucid as Nick... things would be very different I'm sure! Great video as always. Thanks for the content!
They could try, but only Nick is Nick Lucid! Hey, you should trademark that somehow Nick.
Amazing content -- one of my favorite RUclipsrs out there.
You can obtain content enough from the textbook plus the great teachers like Nick on RUclips, I wish it had been around when I was at school. Obtain the info, complete the exam. Simple.
Wouldn’t a spark gap make the circuit open.
Teachers don't get a month to prepare for a 15 minute lecture.
Thank you for the incredibly lucid explanation! Came for getting a few doubts cleared, and left appreciating capacitors a lot more :)
I'm in avionics, and it's been a while since I've had a refresher on electrical components, this is way better than the way I was taught
I finished an AC circuits course last semester. Much appreciated
7:50 - I was an electronic technician in the Navy, I was then an electrician for 10 years, I then went on to get bachelor's and master's degrees in electrical engineering. Long story short, I have a lot of experience with electrical teaching techniques.
Anyway, I have never heard this diaphragm analogy for a capacitor. I like it.
The diaphragm analogy was the way I learned it as a kid (or at least a very young person). You must have been very unlucky not to hear about it.
We learn something new every day! And it's a big world. Knowledge doesn't spread evenly 🙂
@@localverse that's for sure, the more I see and lurk around the more it is confirmed that knowledge spreads greatly unevenly
10:38 Oh right! So _that's_ why doping a semiconductor makes it a better conductor -- it doesn't give any more energy to the charge carriers, just means _more_ charge carriers are free to move around. I'm currently taking an EE class on semiconductor physics and we're finally getting to the parts that relate to electrodynamics (as opposed to the lower level stuff that's all quantum mechanics and statistical chemistry) so that's what came to mind rewatching this video. It's amazing how _connected_ everything is in physics.
I really appreciate this deeper dive into capacitors. When I first started studying electronics, capacitors were always where I got tripped up. This was very helpful.
Glad to help 🤓
You could have been best Professor in any great University. You make most complicated concepts sound simple. I respect you a lot.
When I was an engineering student in college, we had to take Physics I and Physics II For Engineers, so we got both the physics and the engineering of capacitors. Fun stuff.
I did a few years of maintenance and HVAC work and I always wondered what exactly is going on inside a capacitor! I remember asking my boss about it and it kind of went over my head so I always just figured they were kinda like those huge rechargeable portable batteries you can use to charge your phone. This really broke it down and I can say I get it much more now. Really cool!
Happy to help 🤓
Flirting with the Veratasium debacle without touching it? Love your channel! Also, any thoughts on Veratasium's assertion?
10:50 he was years ahead
@@JabranImran maybe. Veratasium make a specific assertion. Uses the word lies. Says energy will arrive in speed of light pretty much regardless of the wiring diagram. Etc...
Nick commented on Derrick's video directly. He was of course supportive and warned him of comment trolls.
@@playgroundchooser hmm. Unsure who is trolling whom here. I'm of the opinion Derrick is trying to assert science without experiment. Might even call it trolling, but I'd avoid that word.
@@BenjaminGatti Oh, no no. I mean that Nick warned Derrick of trolls in his comments, not you my man. You bring up a good question. I think Nick is more about the physics (the math itself) behind the problem.
Capacitors are just like synapses between neurons. Jumping "variable current" from one edge to other edge of the capacitors periodically as so called "the resonance" or ""oscillation"". It is sensitive just to the CHANGE as much as its RANGE(capacity, Farad). It is also something like bedroom lamp which shines while movement continues back and forth. When "back-forth" voltage change is extinguished, then it will be sleep time for the lamp...
"If your capacitor is literally shining, you're having a bad day." Unless you're ElectroBoom making a video, then it's perfect.
I really appreciate how you take the abstract and complicated things and make them fun to learn as well as easy to understand.
Haven't seen anyone better than you explaining this. Thank you so much! Congratulations!
I am an audio engineer, and we use these things called transformers all the time... they block DC, but allow AC to flow... therefore allowing our digitized sound to flow, but blocking the DC used in many of our devices. A transformer is a capacitor, but instead of it just being nothing in the gap, its a separate wire entirely that essentially carries the magnetic field of one cord and then imprints it on another. This happens in your microphone on your phone, and the speaker on your phone! Not to mention likely several other places on the phone.
Love to see SA referring Electroboom in the video. I love them both. One is a brilliant theoretical physicist and the other a brilliant Electrical engineer. My knowledge about electricity (both AC and DC) has increased a lot by watching videos like this.
I am intimately aware of them due to condenser microphones, I looovvveeee the science of capacitance
I love your videos and am stoked to see you doing one on this concept!
I am a lifelong retired electronics & software engineer, and all this physics BLOWS MY MIND!
Pointing vectors AGAIN! My head CANNOT TAKE IT!!!!!!!!!!!!!
I use maths a lots sometimes for circuits, but you physics guys are on a different level!
Us physicists like to understanding things on a deep level, often deeper than is necessary to do anything practical with it.
I think "The truth resists simplicity." is the best analogy I've ever heard for how the world works.
Wow... that was a golden 10 minutes lesson.
Learned more now than with prep courses into university and a whole year of electromagnetism in a geology major!
Thanks dude!
This was awesome! I always hated the typical capacitor explanation but didn't know why until today. It's because "the truth resists simplicity"
Nice!
It's just been since last semester that I took a course in introduction to physics 2 where we learnt all around electricity, magnetism, circuit components and it's still so amazing to see just how weird and magical energy behaves
Hey Nick, I loved this video! As an Electrical Engineer, I was also kept fascinated by the way in which this beautiful thing works. All my imaginations and understandings about capacitor were proved right here! Ahh! I feel so happy right now! And that capacitor energy flow is really cool. Thanks a lot Nick! ❤️
Glad you enjoyed it! 🤓
That explains a lot, capacitors always seemed like an exception that showed that the rules taught in electronics in school were just a vauge simplification. Thank you!
Honestly, I hoped you'd expand on the superconductor bit, given that you can hear basically everywhere they're exactly zero resistance.
Saying "superconductors have zero resistance" is easier and sounds more confident than saying "their resistance is below our ability to measure." It's laziness.
@@ScienceAsylum That's kinda disappointing, but thanks. I guess I should read up more on them.
@@ScienceAsylum oh wow I never noticed!
I just looked at an experiment where they use very low currents to avoid heating the sample. How would it heat up if there was truly zero resistance ;)
I'm sure it's much more complicated though, with all the different types and stuff...
@@kylebowles9820 Superconductors have a maximum current above which they cease to superconduct, so yeah the current does need to be controlled if you want to actually have a superconductor
@@triffid0hunter i think the point is that per the conservation of energy, if current generated heat, any amount, there must be resistance.
If the resistance was truly zero, heat could not be generated by the current.
Thanks for teaching me about the Poynting Vector for the third time....I forget once every score years.
Your stuff is helping out. I learned electronics theory in a Vocational Radio & TV Repair class. The Instructor only briefly mentioned the EM Field and the Poynting Vector, but didn't get serious about it or quiz us on it.
In Electromagnetism Physics class, I got the whole gory treatment.... but never really blended it with my electronic circuit theory memories.
40 years later, you helped finish the job.
Glad I could help 🤓
You are the best teacher ever! So many times now have you managed to teach me something new about something I already thought I understood, and in so doing made the knowledge intuitive instead of memorized. You rock!
As an electrical engineering student, even my mind was blown with your explanation! Good work! Thank you for learning this!
Mind. Blown. I was looking through a powerpoint that louis rossmann made that gave a rough overview of electrical engineering (just enough to do electronics repairs) where he said that capacitors block DC but allow AC to pass. It seemed so counterintuitive that I was certain he made a typo. I though for sure it should be the other way around. But this video really shines a light on why it works the way it does! Thank you for all your hard work making these videos! 💯👍
Glad I could help 👍
There is also the opposite, a device that "blocks" (hinders) AC but allows DC: An inductor (a coil).
@@whuzzzup they both shift current and voltage away from each other in a pepetual transiant state (AC) a capacitor shifts tha voltage behind the current and an inductor shifts the current behind the voltage.
studied 5 years of electrical engineering and never found these. god thank you
Dear Nick,
there is still a simplification in here:
In 05:20ff it's suggested that all the wire and both plates of the capacitor are completely neutral as long as the switch is open.
This cannot be true since the battery is already connected with the wire at both sides, meaning that the later positive plate must already be slightly positive at the beginning to be at the same potential as the plus pole.
What's the minus side then?
It must be the near (seen from the battery) side of the open switch in a way that this and the later positive capacitor plate act as a capacitor of extremely low capacity which means the same voltage at an extremely low charge. The rest of the wire, including the later negative plate of the capacitor, act as a kind of dielectric since they get a slight charge gradient via influence.
I love understanding things beneath the abstractions, especially with electrical components, looking forward to more videos like this
Best depiction of real science I have ever seen in all the youtube science channels
This is what ALL PHYSICS is all about 4:26
It's not fun like laughing and smiling or watching a 5 minute video and saying "Now I understand"
It is fun in this way 4:53
One of my great embarrassments is that i never learned electronics along the way. Not without lack of trying, but most of the resources I've had over the years gloss over so much in a don't-worry-your-pretty-little-head-about-it way. I crave a deeper understanding, and your videos have been one of the best resources I've run into to gain that understanding. Thank you, Nick. I hope you do more of these-and any time you want to create a dedicated electronics course, I'm totally there. :)
How long did it actually take you to derive that expression for V_c at 4:53? I'm glad you showed the actual math even if you sped it up so viewers didn't have to watch, because I paused it abd worked through your algebra, which reminded me how transient analysis actually works. It also made me realize what I don't think really hit me when I learned it in class a couple years ago: its really just applying boundary conditions to a D.E. general solution to get the specific solution. So many E&M problems come down that process.
It took about 30 minutes, including all the mess ups. It was about 12.5 minutes for the final sheet. Apparently, I'm a little rusty.
What does D.E. mean? (merely curious, I've no idea about any of the math)
@@localverse Differential equation(s). To briefly summarize what I was talking about, a differential equation is simply an equation involving derivatives (if you haven't had calculus, a derivative is a function giving the rate of change of another function; e.g. the derivative of f(x)=2x+5 is f'(x)=2). Since rate of change is such a broad concept, D.E.'s show up all over the place in physics (and other sciences too). In regards to capacitors specifically, the equation that describes the charging of a capacitor is the solution to a D.E. The actual equation, for a circuit with just a resistor and capacitor (which is the type of circuit Nick showed in the video) is I(t)=(Vₛ/R)e^(-t/RC), where Vₛ is the voltage of the power source. It essentially says that the current will decrease exponentially with time, starting with a value of Vₛ/R and decreasing at a rate depending on RC.
@@Lucky10279 as someone who tries to follow physics but is rusty on the math (2 decades since I took calculus), this was probably the single most useful / impactful youtube comment I've come across.
Now I have to go back and re watch some of those Sean Carroll explanations.
Thanks!!!
@@uninspired3583 Glad you found it so helpful! :)
i'm just going to say you're leaps and bounds better at explaining this sort of stuff than anyone else on youtube.
"The charge must flow!" - 😂I almost didn't get it - classic!! Thanks for another great video - wish I'd had a science teacher like you at school - what a difference that would have made! Could say the same for my theoretical physics courses at uni sometimes too! :)
I'm glad you appreciated the joke 🙂
I almost didn't get it.. and then I fully didn't get it.
@@whatelseison8970 In case you’re actually asking for an explanation: It’s a reference to Frank Herbert’s sci-fi classic “Dune” and the phrase “The spice must flow”.
@@whatelseison8970 see? transient state!
@@germansnowman fun fact, "the spice must flow" is a phrase used in movies and mini series based on Frank Herbert's work, but he didn't use the phrase in the original novels.
I'm 42. And this is the first time someone adequately explained to me how capacitors work. Bravo. It's about time.
Awesome. Glad I could help.
Dang it. Now I understand inductors better as well. Their kinda inverse relationship with capacitors was always fascinating to me! Thanks.
This is brilliant. I'm an Elec Eng of 30+ yrs and still got something out of it.
Loved the paper work scene.. such a great insight to a scientists life 👍
Cheers Nick ❤️
Best explanation ever, for two reasons.
First the modelling makes a difficult concept much easier to visualise and understand.
Secondly is the nitty gritty details for those who want to delve a bit further.
It definitely IS a beautiful abstraction. The energy flowing from the battery to the capacitor not by electrons being pushed on one plate and removed from the other (that is only charge being moved) but through the EMfield from all around is still a mindshift for me. Waiting for the coils now :-) .
Actually, the only physical thing is the movement of charge (there are separate components for the velocity and acceleration which behave very differently). The magnetic field is just something we measure as a result of moving charge. And the energy is just a mathematical abstraction for bookkeeping. At the fundamental level there are just moving charges influencing each other with a time delay due to the finite speed of light. We describe that by convenient notions of electric and magnetic fields and the even more abstract notion of energy. The electric field is the part we would measure if the charges weren't moving. The magnetic field is essentially just the adjustment we need to make because the charge moved from the location where we would have otherwise measured it to be and that "information" took time to reach us.
Thinking of energy as some kind of substance flowing into a gap is also not really that helpful. It's not really a physical thing that moves. The actual physical things that move are the charges. The rest is just something we either measure or something we use mathematically to do bookkeeping.
Of course the whole thing gets really wild when we introduce quantum mechanics, where radiation (one of the two components I discussed above) is considered. We know it is quantized and we have absolutely zero idea what a measurement actually is physically in this context. Anyone who tells you we do is just making stuff up. The measurement problem is a major unsolved problem in physics. But at a deep fundamental level we need to distinguish between what is physical, what is measured and what is bookkeeping for convenience but totally nonphysical and non-measurable.
For example, set up a permanent magnet in a static electric field. The Poynting vector then says there is energy flux in some direction. But good luck measuring it. It does not correspond to something physically measurable. (Mathematically it is intrinsic angular momentum, i.e. angular momentum when you are not having angular momentum. You can demonstrate it must have been there by doing certain tabletop experiments, but ultimately it is just something that we infer is there for bookkeeping purposes. There's not something actually spinning there in the gap between the magnetic poles and the charged plates!)
@@goodwillhart 👍 wow, thanks for this reply, insightful and also more things to think through ... thanks and best wishes for the new year!
Science starts becoming interesting when explained by amazing teachers like you!
Thanks! 🤓
Addicted to these videos. I've just covered capacitors in Grade 12 - this would've been a great addition.
As an electrician, I have to say your videos explain the actual physics of electrical circuits in much more realistic detail than I ever learned in school. Thanks for your explanations and great work as always.
Thanks! 🤓
Wow this is so well explained. Always found them exciting! Thank you Nick!
I have a pretty cool story about Capacitors from when I was in University. I was in a circuits lab where we were measuring electric waves with an oscilloscope at different frequencies but we kept getting this 6 GHz signal mixed into our wave, for low frequencies we could basically ignore it, but by the time we were measuring a 1 GHz one (the highest frequency we were working with) it became impossible to ignore while getting anything resembling good data (it probably was messing with our accuracy before that I just don't remember that well). Anyway, we asked the TA that was running the lab, but nothing he suggested worked, but finally we asked the Lab Tech who looked at it and put in a capacitor (or 2, I can't remember the details) in the circuit and the 6 GHz signal vanished, because a capacitor acts as a short for high frequency signals so the high one just drained away (or at least that's how they described it) and we could finish the experiment.
I worked as a university lab tech for a while. Always ask the lab tech!
Anyone else still having PTSD from the Veritasium video?
I always think of a capacitor as a DC blocker, but one that allows more current flow as frequency increases, depending on the resistances and impedances in the circuit.
I'm old school!
A teacher of teachers. Very precise, concise, and all around just nice. Keep up the good fun and happy new years! Oh yeah, capacitors really are super cool! You know what has a diaphragm? living things, for their lungs. It seems that our own circulatory system can be used analogously to an electrical circuit, hmm? Heart, as the battery; capacitors, for the lungs. I wonder what other analogous electronic parts fit?... Also, there's about to be a revolutionary new capacitor coming out soon that I hear will replace LI batteries.
This video is simply BEAUTIFUL! I'm familiar with almost all of the terms you've used in this video, Displacement current, Poynting vector etc. But it's only know that I've actually understand what happens. Thank you so much for this
I am an EE student. Thank you sir for this explanation with a physical analogy.
You're welcome! 🤓
@@ScienceAsylum I think Nerd Clone replied to me, even the emoji have specs XD.
I knew this video was going to be made after Veritasium made the video about electric flow. Great visuals and fabulous explanation
When we deal with grounding of various parts of Space Flight batteries we have to qualify parts in milliohms. Basically, our connections have to be at wire resistance levels.
Good analogy using the membrane as reservoir of energy, which will be restored when pump is off. Just as condenser work. Hats off
If this dude took psychedelics while *scientifically and mathematically* analyzing whats happening in neither a spiritual nor a mocking manner we might be lookin at the next Nikola Tesla for real.
Over the years, much of my understanding of math and quantum mechanics has come from analyzing my psychedelic experiences and my lucid dreams. Ive been a math and science nerd growing up and i really looked at everything like a math equation or theorem to be solved.
I NEED to know "why" for everything. So simply having my brain do unimaginable things was not enough. *Why* is this happening??
This channel has coalesced alot of my understanding into pure knowledge since ive found this channel a month ago. Man so many of my experiences over the years make so much more sense now its freakin powerful and weird AF. Literally kno other channel ive seen has done this youre like, a whole thing kudos
checked over 10 videos in youtube, this video so far is the best one...the capacitor is actually important for balancing current...
What I learnt till now is, "Happening something is easy, but explaining and reasoning about it is really hard..."
I worked for a passive component company for years and this is an excellent explanation.
I'm always in awe of the people that figured these things out when everyone else thought it was magic... I can't even understand it when it's thoroughly and reasonably explained! I'm pretty sure capacitors are magic... :D
Can you read my mind? Cause I was watching your video about how energy actually flows in a circuit on 28 of December, and today you've done this one that further explains how things works . I love it 😍
I'd like you to explain what happens when the capacitor discharges.
Same thing, just in reverse.
Great video - a few things that would be worth mentioning (for the you know, practical folks...) First, is that a dielectric will increase the capacitance, by the relative permittivity. Second, the charge on the capacitor is proportional to both the Capacitance and Voltage (Q=CV). Finally, the energy goes as the square of the voltage (E=1/2 CV^2). Many thanks once again!
Although my knowledge of quantum mechanics is limited, I appreciate this video as a metal fabricator. If a capacitor in my welder goes bad, the welder will still work but with reduced performance...way reduced.
We learned a bit about these when I was in welding school, in particular that you needed to be aware of them if you were doing maintenance. Cool to learn a bit more!
I like that he doesn't even change shirts, he just puts a lab coat on.
i'm a first year EE student and i love this, it's getting me really excited to start learning this stuff in class
It's cool stuff 🤓
I'm a welder, I've always been curious about the physics involved with arc welding, we usually run electrode positive DC circuits with welding rod, and the heat tends to focus in the base metal, what is actually happening in the arc?
Very good question ! That’s plasma physics goin’ on in there. I guess Nick can do a separate video on that.
With SMAW (Stick welding) the electrode positive polarity makes the rod actually get consumed, which drives the arc characteristics and such.
It's the opposite with GTAW (tig welding) where there is not a consumable electrode. For tig welding, it's DCEN (electrode negative) and that makes all of the heat go into the base metal.
I’ll explain this in electron current flow, not traditional current flow. Stick and MIG welding are DCEP (direct current electrode positive), meaning the ground is hooked up to the base metal. TIG welding is DCEN (direct current electrode negative) meaning the positive is hooked up to the base metal (except on aluminum or magnesium, where the cleaning action/heat management of AC alternating current is needed).
In stick welding, you are creating a net negative charge on the base metal, hooked from the - cable on the voltage source. This happens because it is more electron charge dense in relation to protons. The + cable on the voltage source is hooked to the welding stick, and creates a net positive charge, because electrons are pulling them from the stick and into the voltage source, so the stick is less electron dense in relation to protons. When the positively charged stick touches the negatively charged base metal, electrons are violently pulled from the base metal into the stick. This enormous amount of heat creates the arc that allows the stick to be fused with the base metal. It doesn’t matter if the electrons are being pulled from the base to electrode, or vice versa. Because in TIG welding the electrons are ripped from the tungsten electrode to the base metal, which is the opposite of MIG/Stick. And in AC welding, the electrons are constantly being pushed/pulled each way- like TIG polarity, then MIG polarity, 120 times per second. The heat and ionization is the important part.
In the presence of oxygen, it wants to pull electrons from the metal and give it to the oxygen, and over-oxidize the material. That’s why you use more inert gasses, so electrons can’t be stripped and over-oxidize your material. Inert gasses do not pull electrons from your material, making a smooth transition of electrons from stick to base, and thus don’t oxidize them. Inert gasses do not have available electron-empty spaces in their outer orbitals to steal them from metals. Different Inert gasses are chosen for specific metals too, because electron properties are different for both.
@@rebeuhsin6410 Stick welding uses flux on the outside of the stick, that coats and vaporizes as an (inert) gas over the welds. It serves the same function as inert gases passed through a nozzle on MIG welding.
TIG uses a non-consumable tungsten tip to create the arc, and a metal consumable rod is used while fed in.
The air gap between the electrode and the metal plate is a "resistor" an invisible one...5000volts per centimeter and lower at like 500 volts per mm... That gets multiplied by the amperes...
Equals wattage.,. You control the gap with your hands.. Your actually controlling the resistance bigger gap more resistance less amperes... Closer narrow gap is less resistance more amperes.... More electrons more heat . More melting
When I first learned electronics at college 35 years ago, understanding actually how capacitors worked... well, I simply didn't. I just accepted that they blocked DC but 'somehow' passed AC with the plates charging and shit, lol. Even diode and transistor theory seemed easy by comparison. I think capacitors, along with their varied uses, are a wonder within electronics... no, they're the unsung heroes!
I agree that they're pretty amazing.
I often use the water analogy for trying to explain voltage and current... But I had never seen your example using the rubber dam inside the capacitor ! That's pretty good !
Next, I suppose you will be talking about the dielectric constant. Or not. 😍😀
I studied capacitors in this way on my engineering career, we had a subject that studied almost every component of a circuit but in a physic/theoric way. Was really interesting.
When I used to play with capacitors as a kid. I used to imagine a tiny flywheel inside of them. Thx for explaining! That was great!
Now that WOULD be a good metaphor for an inductor, since it resists changes in current, kinda giving some metaphoric 'inertia' to the current in circuit
Caps are much more like springs or elastic bands. In fact, there's an old timey unit for inverse capacitance called "elastance". It's a better analogy when you think about the polarity of the voltage as you force charge onto the the plates - that is, it comes back out the same way it went in. On the other hand a flywheel only stores up energy as you accelerate it and releases it when you try to slow it down but the wheel only has to go in one direction through those changes.
They also behave similarly in that you can charge a cap just like you can wind up a spring and they can both just kinda sit there charged up until you get the energy out because it's being stored as _potential_ energy. In an inductor the energy is only stored as long as current flows just like a flywheel needs to be spinning to store it's energy. In some sense they both store _kinetic_ energy.
And because there's a natural duality between potential energy and kinetic energy a cap connected to a coil will hand their energy back and forth at a particular frequency the same way a flywheel hung off the end of an elastic will spin back and forth.
@@whatelseison8970 is that like pulling back a rubber band and flinging the charge? (or a slingshot)
@@tk4x431 does it keep the flow of charge consistent too like a flywheel would to acceleration?
@@localverse Yes. That is what an inductor does. It reacts to an attempt to change the current in it, and applies a voltage to the rest of the circuit to oppose this change.
A capacitor would be analogous to elasticity in the mechanical world, where energy is stored in the form of potential energy by virtue of position/configuration. An inductor is analogous to inertia, where energy is stored by virtue of motion. Resistance is analogous to viscous friction, where energy leaves the domain of reversible processes and is converted into thermal energy. Like resistance requires a voltage drop across it to sustain a current, a viscous friction requires a force to sustain a constant velocity. For viscous forces, it is proportional to velocity. For other regimes of fluid resistance, it is a lot more complicated and extremely non-linear.
Your channel has been so educational that I understood what this video was essentially going to be about from the get go.
a guy in one of my electronics classes ended up with a mark on his face when he hooked up his electrolytic capacitor backwards and it got real shiny real quick... instructor took the opportunity to point out 2 things:
1. make sure you're hooking up your electrolytic capacitors correctly.
2. this is why we wear safety goggles.
Ooo shiny
Thanks, Nick, for your improved Poynting vector graphic which now clearly shows that the energy flow density is greatest nearest the conductor and then drops off further away from the conductor (specifically the Poynting vector magnitude is inversely proportional to the biquadrate of the distance [square of the square, or 4th power] away from the conductor). This means that almost all of the energy flows along the surface of the conductor.
Love the ending: "That means energy flowing inside fields is an abstraction inside of another abstraction. But it's really beautiful to look at, isn't it?"
Pretty much. Physics is _full_ of abstractions on top of abstractions. Computer science and software engineering have got physics beat in regards to the sheer _layers_ of abstraction they use though.
That's the best explanation of the Veritasium video so far!
3:12 The shining state of capacitor doesn't last very long.
It quickly changes it smelling state of capacitor.
Indeed.
I love the smell of burning dielectric and ozone in the morning - Circuit apocalypse.
I just finished understanding Displacement current and Maxwell's equation from my physics book and you dropped this video this made them more clear to understand. Thanks Nick!
Glad I could help! 🤓
I get it that theoretical physicicists eschew practical matters 🤣. In practice though, the internal resistance of the battery is more significant than the resistance of the connecting wires-the latter can usually be ignored. So when analyzing or designing circuits, we engineers model voltage sources with an explicit series resistance (Thévenin's theorem). Coincidentally, for the circuit that you were analyzing, it gives the same result that you got by assuming that the wires have a significant resistance. Lucky you!
super usefull, thanks ! first time in my life, I could visualize how initial current flows thru the capacitor.
3:01 Electroboom: Everyday is a bad day
Great video Nick, from the El.Eng. perspective I would only add: the main application of capacitors is to build circuits which can filter frequencies, i.e. through capacitors we can select and isolate frequency ranges in the perturbations of the electrical field. That has applications in basically any useful electronic device.
What happens right around the wires? The energy is flowing along the fields around them towards the light bulb, capacitor, etc. In some places, it looks like it's flowing away from the wires (e.g. near the battery). But if the wires are experiencing resistive heating, then they must be pulling energy from the fields. Does that go into the wires from the outside? In which case is there some particular distance from the wire where energy is not flowing at all? Or some kind of "event horizon" where energy will either end up going into the wire or into the device?
*"But if the wires are experiencing resistive heating, then they must be pulling energy from the fields."*
Yes, while most of the energy goes into the light bulb, some of it does go into the wires (from outside but is immediately turned into heat). The exact direction of the Poynting vector depends on resistance. The Poynting vector near a conductive wire is _ever so slightly_ slanted toward the wire.
This is why we have grouping factors and balance runs with return paths. It’s extra interesting when you think what is actually happening, it’s so counter intuitive!
Never saw that detailed explanation of capacitors working mechanism.👍
One of the best video of your channel.