The Amazing Eddy Current

Hi, do you know what Eddy Current is? No, it's not some sort of ocean currents that Nemo's father traveled to Australia with. *Although* the name comes from some swirling water currents. But I don't care about fluid dynamics! Eddy current is an electric current that's created in any conductor when there is changing magnetic fields around and those currents make any conductor magnetic. What you have probably seen as an effect of eddy current is that throwing a magnet through a copper pipe... Slows the magnet down. This is paper though. I didn't bother buying a copper pipe just to add it to my collection of unused pipes here. I'm pretty sure it's easy to make one at home though. All I need is an aluminum foil. I wrap around my paper pipe and tape it. Now my magnet drops through air at this rate and through the pipe... The exact same rate (?) *POP* F*** Thanks for cheering me up! Well, I guess that's why we need to know how things work and so in an attempt to fill your brains, [Jazz music] This video is sponsored by Audible because the more you read the more you know [Music pauses] ...except with Audible you listen, you don't read. [Music continues] Which is even better! You don't need to sit down and read a pictureless boring book. Your hands are free, your eyes are free So you can do your normal activity while being fed an entire book. Now, that's efficiency! [Music pauses] (Ow) [Music continues] So go to audible.com/electroboom or text electroboom to 500-500 and get your 30-day free trial and listen to a book you like and you can be well read too [Music pauses] Well listened? [Music continues] Thanks to Audible with the largest selection of audiobooks on the *PLANET*! *thud* *thud* What why the hell is it not slowing my magnet, let's see if we can figure it out The whole thing can be explained by Faraday's law, you know if we move a magnet close to any conductor It creates electromotive force or voltage across the conductor. In simple terms voltage or electro-motive force is equal to the rate of magnetic flux change in time through the surface of a loop Which is also equal to the closed loop integral of electric fields over the same loop So when I move a magnet over a metal plate and change the magnetic flux through it I create current through any given loop which is equal to the voltage divided by resistance of the metal plate in that loop This is eddy current the lower the resistance the higher the current. It's all good and dandy What why do I expect my magnet to slow down when it passes over a metal plate? It's due to something called the Lenz law. Basically what it says is that the world hates changing currents and magnetic fields See when a changing current creates changing magnetic field around it those fields generate a reverse current in the same wire that opposes their creator current and tries to stop it It's kind of like when you push on a wall it pushes you back These changing fields can create a changing current in a second loop that new current is such that it creates these Fields that oppose the original fields and try to kill them everyone tries to kill their creator It's just a hate-hate relationship but the enemy of your enemy is your friend if this current tries to kill those Fields and those fields try to kill this current then these two currents are friends what those idiot Opposing fields don't realize is that while reducing the overall fields They are actually reducing this opposing current which means more current runs into the main loop Pushing the amount of fields back up. This is how transformers transfer power from primary to secondary Pulling current from the secondary output results in pulling more current from the input now Opposing fields repel each other because it means that they are coming from the same magnetic poles you can see this by the jumping wire loop see if I have a coil and I place a wire loop on top of it and then Energize it with a changing current The coil creates these changing fields through the wire loop that creates this changing current that creates Opposing fields that repel each other and the ring jumps up. So here we are I place my loop on my coil and I run 10 amps through it And the disappointment ensues Just there's a tiny wiggle. I think we need more current Fine, I'll use my super capacitors to run hundred amps through it. Okay, the capacitors are charged to 20 volts and watch the ring (ow) Hooh (ElectroOWL) My coil totally melted I will NOT fail at this. See connecting it to a DC voltage creates a very strong but very short pulse of magnetic field change If instead I connect it to an AC source, it can provide a continuous push I'm going to use my entire spool of wire as my coil And then I need an iron core to go through the coil there I'll use my wrench handle for that and then I'll just power it from 120 volt AC Okay, here we are and here's a ring if you can see it and... [Loud spark] Whop! (ElectroOWL) Oh, it did jump. [Loud spark and dirty 60hz noise] Hey, but look at this [Loud sparks and dirty 60hz noise] It's dimming my entire home lights how much current is it drawing? How much is it? [Dirty 60hz noise] Like 36 amps how come my f****ng breakers are not popping. I literally have four breakers 10 amps in series Let me switch to my longer spool. Maybe I can run it continuously Holy Sh** [Everything rattles as Mehdi tries to open the window, I guess?] F*** [Clock tips over and something falls onto the floor] F*** [Very angrily] LOOK! My hundred feet of wire *melted*! F***! I'll use the original spool of wire... which looks a bit shorter, is it melted to some extent? hehe And an autotransformer to limit the current below 10 amps before I set the house on fire Here we go There you are The ring is floating because of the opposing magnetic field it creates and if I change the voltage It goes up and down. I created a voltmeter! [Excitement fades] that's drawing 10 amps Okay so eddy currents through a metal plate should work the same way too They should create opposing fields that pushes the magnet back and slows it down Of course we're talking about non ferromagnetic metals that the magnet doesn't stick to already but then Why the hell is the magnet not slowing down? Hmm... I think I know why. See, the strength of opposing magnetic fields depends on their strength of eddy currents and eddy current is equal to the induced voltage or electro-motive force divided by resistance The voltage is created by these moving fields and depends on their strength and how fast they move I'm dropping a strong magnet very close to the foil. So the only remaining factor is the resistance of the foil aluminum has around double the copper resistance and it's pretty thin - Okay, then to reduce the resistance. I'll use the entire pack of aluminum foil [Did you inhale helium?] Yes! It's slowing down! :D JAAH! Here's the magnet to the thinner foil Dang! just drops and here is a similar magnet through a thicker one. eeeEEEEeee if I pick a bigger diameter magnet that gets even closer to the foil... eeeEEEEEEeeeee Goes down even slower Wheeeeeee! Beautiful Beautifuleeee Beautifuleeeeeeee Beautifuleeeeeeeeeeee Beautifuleeeeeeeeeeee! hehe So slow! I suppose it could work the other way around too like a metal ring going down a magnets Here's a loop of wire and an empty roll of paper. And if I put the wire around it... Just falls. But if I put a column of alternating magnets inside the paper and put the ring around it, you see it slows down because of the currents created in the wire. It's interesting. The smaller the resistance the higher the eddy currents and the slower the magnet drops I wonder what happens if the resistance was zero... [Mind Blown!] Now I get it haven't you seen those superconductor videos where the Superconductor is levitating or as they call it quantum locked above or below a magnet in space This is exactly why a zero resistance Superconductor is locked in position remember current is equal to voltage divided by resistance So if the resistance is zero, the voltage must be zero otherwise We would have infinite amount of current that would create infinite amount of magnetic force from Faraday's laws zero volt or electro-motive Force means that D Phi over DT must be zero Which means there cannot be any change of magnetic flux in a superconductor That's why a superconductor can lock in space when we bring it close to a magnet We create huge amounts of eddy current through it that don't die away because there is no resistance those currents create fields that oppose any change in the fields of the source now in that position the superconductor will not move away or towards the magnet because any motion that creates changing magnetic fields through the Superconductor would create huge currents and fields that would oppose that motion So the superconductor is a stuck in space and can only move in directions where the fields remain unchanged with respect to the superconductor So eddy currents can be pretty cool and useful like in an induction cooker. The cooker radiates very fast changing and strong magnetic fields that create huge eddy currents through a metal plate If you use a high resistance metal plate like iron as they use in some pots and pans, it generates a lot of heat Wow, it's getting glowing hot here. But in a lot of cases eddy-current can be pretty [Sheephdi Mode] ba-a-a-a-a-ad [Boiling sound, karma!] Ow! F***! (Ow) So eddy currents can create a lot of heat in iron cores like this one Transformer cores motor cores or basically any inductor. That's why instead of a one piece iron cord they use multiple layers of coated an isolated metal plate glued together This prevents a huge eddy current to be created through the entire core and a lot of power is saved Although I'm not sure if in this specific transformer, they ruined it by welding all the layers together Maybe some idiot thought it was a better way to hold the layers together because I haven't seen something like this in other Transformers or maybe in fact, this is by design and makes it work better. Let me know in the comments. Aaand of course! Audible! If there's anything that can help me read more books It's by not reading any thanks to Audible, you know because ears... So sign up at audible.com/electroboom or text electroboom to 500-500 And claim your 30-day free trial and book. You will get smarter in no time, and you don't even lose your eyesight Because you don't read you can cancel your membership anytime and get to keep all your audiobooks And if you must know I picked Nikola Tesla's autobiography and I'll rate it - it's not rated. I like him. Although I feel like autobiographies might often be biased and then maybe afterwards I listen to some other important people's biographies and then I'll switch to What is eroti--

Channel: ElectroBOOM

Views: 2,322,406

Rating: 4.949461 out of 5

Keywords: educational, electrical, ElectroBOOM, science, electronics, engineering, entertainment, equipment, measurement, experiment, mehdi, mehdi sadaghdar, arc, mishap, physics, Sadaghdar, test, tools, circuit, funny, learn, shock, spark, discharge, eddy current, magnet, magnetic force, magnet through copper, opposing fields, generation, regeneration, coil, induction, inductor, metal core, iron core

Id: u7Rg0TcHQ4Y

Length: 12min 17sec (737 seconds)

Published: Mon Feb 11 2019

Reddit Comments

[u/Sack_of_Fuzzy_Dice]

It amazes me this guy isn't dead.

[u/_TechnocratiK_]

So at 11:05, the flux path through the transformer is vertical (from the camera's perspective) on the plane closest to the camera. If the welds are only on the outside (i.e., they don't wrap around to the face adjacent the windings), they do not enclose a surface through which flux is passing. Therefore, although they form a conductive path through the layers, they do not form a closed loop around a non-zero net flux (except for leakage flux, which is negligible). Put differently, although I can construct a conductive closed loop through the welds and two different layers, there should be little-to-no net flux through any such loop, and thus no eddy currents, since the magnetic field is in the plane of the layers inside the core, and in the plane of the welds on the boundary.

[u/liarandathief]

I created a voltmeter...that's drawing 10 amps.

[u/LamboDiabloSVTT]

0:14 "But I don't care about fluid dynamics"

Don't let /u/MrPennywhistle hear this!

[u/Enigmaburrito]

This is what Eddy Current is in Australia. https://youtu.be/pIX6YbpJ5wM

[u/Newyorkinthdesert]

Isn’t six amps lethal? He’s playing with ~ 40amps without gloves...wtf?

[u/SoLongSidekick]

Kind of ruins the comedy when you leave a freaking lighter in frame right as you supposedly "accidentally" set a spool of wire on fire. @ 6:00

[u/mr-mercury]

He grew up as a kid who did everything at home.

[u/Langernama]

dope video, boom sir. Now i understand a bit better what feynman was talking about concerning voltages within metals. Let's hope a superconductor at room temperature under normal pressure will soon be developed. This will, without doubt, revolutionize transport and movement of basically anything.