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,
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*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--