Eddy and Lenz' Law Explained

This video covers eddy currents and Lenz' Law using the well known demonstration of dropping a rare earth magnet down an aluminium tube.
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[@HJeff]

The best explanation of eddy currents on KZbin. Thank you so much.

[@PhysicsHigh]

Thankyou.

[@clo7473]

left hand for negative electron flow and and right hand for conventional positive current. The video uses both without specifying which of the electron or conventional flow you're applying, which adds to more confusion to the eddy current with its arrow pointing to the electron flow direction. But for the sake of delivering the big picture concept, it does its job but could be improved if the above mentioned can be more precisely specified so students can have a more accurate understanding.

[@clowdflowtr9560]

This is the very thing I was questioning as soon as the hand rule was initially mentioned. Thank you for the further clarification.

[@andrewjustin256]

Thank you so much for that comment! I was just about to ask this question.

[@rudywijaksono4613]

Left hand is using for induced EMF, and right hand for induced current. Remember the second generated emf after the current induced on second bar. Just like motor electric on left hand and motor generator on right hand.

[@framerate1494]

You just helped me understand more in 15 min than my physics teacher taught me in 3 lessons!!! Thank you so much!

[@GlidyBun]

I had struggled with this concept for literal years until I watched your video. Incredible.

[@chaoyue8412]

Best explanation indeed. Thanks for showing how eddy currents are formed. Other videos usually don't explain this part

[@emilyhancock4391]

Really good - I was lost but now am found. I feel like a real electrical apprentice now. I’ll be able to play handball with peace of mind at my lunch break tomorrow. I owe my life and my trade. God speed big hoss x

[@akhileshwarsingh2974]

I was tired of searching the explanation......but you explanation was perfect.....I completed understood... thank you soooo much ☺

[@hatchedcoast7495]

wow, hands down best explanation i've ever seen. Thank you!

[@yasmine9046]

Thank you for this great explanation and the time you took to make a video of such quality!

[@hightttech]

I've watched a dozen videos on this magnet/tube experiment; YOURS IS THE BEST 👍.

[@PhysicsHigh]

Thanks. Do you see my recent one? 2nd latest which is a follow on

[@cz2563]

Best KZbin video on this topic.

[@shanefrank3281]

Best video on eddy currents I have seen. Most of the others are much more confusing. But I have learned a right hand rule that works where you mention a left hand rule. For the right hand the thumb is the direction of movement, the forefinger is the direction of the field and the current is the middle finger (all orthogonal with each other). Of coursethis works the same way as your left hand rule.

[@PhysicsHigh]

Thanks

[@TekCroach]

❤ Actually the best explanation for eddy current.

[@ppmm414]

Best explanation ever. Pliz keep posting videos like these I have already subscribed

[@happyhayot]

Great explanation, very intuitive, now I understand this completely. Thank you very much.

[@matei5054]

Best explanation on Lenz's law after a tiring search for the same. Thanks!

[@PhysicsHigh]

Thanks. Glad it helped.

[@James-eb7ph]

I think you could explain the direction of induced current using Fleming's right hand rule. Remember that motion is in the direction of the conductor. Relative to the magnet, the conductor is moving upwards (you could explain this to a student to imagine that you are holding the magnet still and pull the tube upwards), now you can use first finger = field and thumb = motion to obtain the correct direction.

[@stanleykania7184]

I am age 46 and entering triangle technical school for the electrician program and watching the videos here maybe helping me for my upcoming classes !!

[@Nal555Seriously]

Thank you. Cleared up so many things.

[@velcroman11]

Back in the day. Micro Farad invited his girl friend Milli Amps for a ride on his mega cycle. It was a loverly day, they cycled over a whiet stone bridge and stopped in a magnetic field for a picnic. ….

[@sarava338]

you actually save my life

[@TalesMason]

You have some great lectures on this channel! Thanks a lot!

[@PhysicsHigh]

Thankyou

[@samuelojimba1516]

Well done

[@H750S]

Really enjoy the videos, learning a lot so thank you. Question about the copper pipe and magnet. I saw another video of a copper pipe with a small slit cut all the way down so you can see the magnet fall slowly. Wondered how the eddy currents could flow and produce a magnetic field when there is not a complete circuit anymore?

[@PhysicsHigh]

Can you share the video. I essence that should not work. As you surmised, there’s no complete circuit meaning no eddy currents and no electromagnetic braking

[@essence7275]

thank you sir

[@CocaKola913]

Great video

[@danielstiller4810]

Really good, thanks a lot

[@anthonyskilton8634]

Superb explanation, thank you.

[@PhysicsHigh]

You’re welcome

[@diamony123]

nice, you also describe what its like dealing with a teenager. more force the more opposition.

[@PhysicsHigh]

So true

[@flabbergasted7237]

you just explained what i have been researvhong for 3 hours in 4 words, thank yiu anon

[@kassahunleta7616]

Simple explanation. Thank u. Keep it up sir.

[@PhysicsHigh]

You’re welcome

[@lucaholmes4157]

absolute legend

[@AlexRamirez-pj9vr]

in the example problem, i’m having a hard time understanding how the magnetic field is opposing the change in the initial magnetic field. i understand the explanation of how we get the direction going upwards inside the coil, but how does this support lenz’ law where “the magnetic field created by the induced current opposes changes in the initial magnetic field” if there are portions of the magnetic field that are actually in the same direction (like inside the coil)

[@semisemi9736]

easy to unterstand, thanks :)

[@chrisyo4461]

Brilliant

[@andrewjustin256]

11:15 I could not wrap my head around this point that whether the drawn induced magnets, one on top and bottom, are horizontally oriented where one pole is going into the screen or are they vertically oriented as the real magnet is. Please clarify that.

[@MrTube310310]

Good lecture

[@sanjeebchakravarty1415]

Thanks for the explanation. But i think it is Right hand rule not a Left hand rule. Kindly edit the hand picture. Anyway a very clear explanation. Thank you again.

[@PhysicsHigh]

You’re welcome. There are two types of hand rules. You are referring to Fleming hand rule which is not the one I’m using I have a video which examines both.

[@divermike8943]

The purple velocity vector is up in the picture. But the magnet is moving down. Correct? Left hand rule? Not right hand rule?

[@PhysicsHigh]

I’m not using Fleming hand rule. See my video on hand rules

[@jordanb5529]

Thank you so much for this! Question - how did you know the velocity of the tube was in the upwards direction?

[@l.t.a821]

relativity in motion

[@surendrakverma555]

Thanks 🙏🙏🙏🙏🙏

[@ainsleyharriott3783]

great video Phill xx

[@PhysicsHigh]

Thanks. Though my name is Paul 😉

[@_programming]

Thank you 🌟

[@PhysicsHigh]

You’re welcome 🤓

[@Hino_55]

i understand it better now!

[@MemeNiche]

Very very clear explanation thank you sir.

[@sunethedirisinghe9644]

Excellent..thanks a lot, I clearly figure out how to eddy current produce.

[@davidcorbett2170]

This may seem a stupid question but could the magnetic fields created by the eddy currents also induce their own currents in other areas of the metal tube ?

[@PhysicsHigh]

not a stupid question at all and a great question. The model that I present is a simplified model and helps explain Lenz Law. But just like projectile motion being parabolic but really simplified (see one of my recent videos), in reality ANY change of flux in a material will cause the production of eddy currents. So yes, the eddy current produced will produce magnetic fields which will cause smaller eddy currents. The end result is probably something quite complex, not the simply circular currents I have drawn.

[@Niglnws]

​@@PhysicsHigh do you mean the transient phase of producing eddy current, the eddy current doesnt increase in no time, so there is changing magnetic field which will induce other eddy currents and so on until stesdy state?

[@-mustang-9383]

So when are we applying left Hand rule and right Hand rule? in right Hand rule, is for current, magnetic field and force. moreover how is it going to be connected with back emf? and in Minute 11:35, i still don't get the idea for drawing the coil and the N S direction, also with the right Hand and thumb. Why did you Point out the thumb is equal to North pole instead of South pole?

[@CosmJJ]

best explanation! thank you!

[@نائلنعمان]

excellent video,thanks a lot

[@james77011]

So, eddy currents, are currents that oppose the original source that created it?

[@PhysicsHigh]

Yes but more correctly the eddy currents magnetic field will oppose the field that created them.

[@freckle3773]

thanks!!

[@txemaglez8251]

Great!!!

[@manojsingh-rm6ms]

Make a video on Lorentz force and how this is help in synchronous machine when we take stator windings.

[@annetteku1]

Can you explain and show what makes a magnet magnetic, Down to atomic particle level.. This question has never been adressed in my experience.. I have tried to imagine electrons fixed in a prefered orbital direction. But why is iron good at Holding a magnetic current and not many other materials? Dont speak about miniature magnets, but how or why iron behaves like this.. if there even is an explanation in science for it...😅

[@PhysicsHigh]

Great topic. I’ll add it to the list. Thanks

[@chronickatie]

I'm confused, in my physics class and my curriculum we were taught that it's the right hand rule, everything means the same thing, fingers are B, thumb is I and palm is direction of F but because it's my right not left hand I have the current in the opposite direction which means that if I did it with my left hand I would be marked wrong. (Unless he is talking about negatively charged particles shooting perpendicular to the field, such as electrons, in which case I get it but I thought we were dong positives

[@PhysicsHigh]

There are differing hand rules around and they can get confusing if you mix them up. I have a video on the hand rules that might help.

[@susannam3923]

i think generally in different countries there's different standards for that? like some places they only teach I as negative charge (the actual flow of electrons) whereas america teaches the conventional electric current. i think. this is what wikipedia says: en.wikipedia.org/wiki/Electric_current#Conventions

[@EB3103]

and what if the magnet will placed horizontally in the pipe? will there even be a magnetic flux?

[@JensenPlaysMC]

yes

[@ppmm414]

I am a university student, I did this in high school but when the topic was introduced today in class. I felt like he was speaking in another language 😂😂😂

[@studyroa9045]

you are using the conventional current or electron flow

[@PhysicsHigh]

Conventional current.

[@studyroa9045]

@@PhysicsHigh thanks for your fast replay

[@jeremyburnum8604]

This is great, but when you consider rotating magnetic fields instead of constant fields, rules change!!!. This is the beginning concept, not the end. When coils are set to oppose Lenz's law and you have RMF...then RMF takes over and you have EMF produced without counter interaction. Learn and grow!!! Don't think of 2 directions. Don't be stuck in your ways of the 2nd law of thermodynamics.

[@dp0813]

Great vid; thanks! 👍

[@lukebitschnau9455]

matey i think it is the right hand law not left hand one

[@keithnguyen6323]

wise man

[@lukebitschnau9455]

@@keithnguyen6323 fax do

[@PhysicsHigh]

There are two versions of the hand rules - If you are referring to Fleming's Rule,, you are correct, if thats the case. There's another one, and that's in common use here in schools, and the one I use here - so also correct - see my video on hand rules kzbin.info/www/bejne/fZ64g5l9aNl0nsk

[@lingyisheng3260]

tq

[@tallguywitham5ivviii557]

I have the most important exam of my whole life in the next 2 months and i gotta say if it isnt bcuz of u i dont think imma pass

[@PhysicsHigh]

Glad I can help

[@Adamvz54]

Great video, easy as to understand, thank you so much

[@akhileshwarsingh2974]

Doubt sir.....what will happen to the speed of the magnet when the copper pipe is cut along its length??

[@sanjeebchakravarty1415]

If the copper pipe is cut along it's length, there won't be any induced current, because the circuit won't be completed. Hence there won't be any induced flux. The Lenz's law won't be valid.

[@dustinbrodie]

Few Questions. Can you use dielectric grease or Vaseline to negate Eddy currents? If I lined a copper pipe with dielectric grease and dropped a magnet down the pipe would Lenz law still take affect but cancel out the Eddy currents? Only asking because I don't have e the material to conduct and experiment.

[@PhysicsHigh]

+Dustin Brodie I'm not an expert on dielectric grease but I can't see this working. It's all about conservation of energy. You cant stop the edgy currents from happening. So any other effect involving the grease would violate LCE. Happy to be corrected by others.

[@dustinbrodie]

Same principle for transformers apply to the pipe if you do it that way. I think it would be better to offset the cuts along the pipe though. That way it ensures the eddy currents will be too weak because they won't have a consistent path to follow.

[@sparkyinwa]

dielectric grease does not stop current inside the copper tube. if slits were cut top to bottom, the circulating currents would become smaller and the magnet would reach a higher terminal velocity but the effect still happens. this is why motors are made from stacked layers of sheet steel instead of solid blocks, the eddy currents are confined to smaller cross sections and the effect is lessened.

[@zahidfaheem3233]

the poles of the eddy currents... shouldn't they have been the opposite according to the left hand rule?

[@PhysicsHigh]

Poles are determined by the right hand where fingers curl in direction of current and thumb points to N

[@zahidfaheem3233]

But the current direction is not conventional since you used the left hand rule to find its direction not right hand :/

[@robertbeed497]

Surely a magnet dropping through a metal tube is acting as a generator and therefore the Right Hand Rule should be used. Reply

[@sparkyinwa]

@@robertbeed497 right and left swap for motors and generators depending on whether you are using electron flow or conventional current flow concepts. it seems like most physics classes are stuck in some time warp where they speak as if electrons have not been discovered and we were speaking of some mysterious unknowable flow of energy.

[@shamsalghadeer1283]

Great!! Thank you ❤️

[@teabiscuit2618]

similalaly

[@leocarlton4364]

chish and fips

[@khaledel-manse497]

Nice Job thanks man :)

[@harrycritchfiled3992]

Surely the magnet falling through the conductive pipe would accelerate as it is still free falling. The magnetic field created by the eddy currents isn't increasing therefor the magnet will accelerate. This graph shows the emf induced as the magnet falls through the tube. It increases over time and so surely the magnet is accelerating through the tube (www.a-levelphysicstutor.com/images/fields/EMI-dropped-mag02.jpg). Hope that makes sense, maybe I have missed something. I'd be grateful for any help Thanks

[@PhysicsHigh]

As soon as the magnet starts to accelerate the rate of change flux increases. Thus the eddy current increase and thus the opposing force. So no, as long as it’s in the tube it will maintain its velocity. The issue with the image is that the coil is very short. If be it was longer than the magnet then you would have a section where the emf is zero whilst in the middle.

[@harrycritchfiled3992]

@@PhysicsHigh thanks makes sense.

[@Niglnws]

​@@PhysicsHigh will it fall because there are losses of current in the metal?

[@divyamgoyal3723]

Thanks for your amazing video. It has really made me understand thoroughly. I would also like you to explain me about the role of eddy currents in induction cooktops as well, please. Thanks

[@ft8925]

Yes point taken thanks .

[@aashisingh4498]

Can you please explain how to minimise eddy currents using lamination ?

[@PhysicsHigh]

+AASHI SINGH I discuss that in my video on transformers.

[@aashisingh4498]

Oh! Sorry and Thanku!!😅

[@txkflier]

Where? He?

[@sanjanavinay6602]

this was a good video ,it will surely help me i would request you to discuss on the topic LC ocillations

[@rakeshbeniwal4737]

This video gives an idea about eddy currents in specific dimensions, but sometimes the dimensions in question is quite different from this video and that would be very hard for me to solve(hsc 2009 Q7). so please explain the concept through different dimensions or point of views to make it completely clear.

[@stikndip]

Firstly, you may want to mention that the metal tube is a non-ferrous metal, i.e. copper. Secondly, what the hell was that palm/fingers/thumb rule? Fleming's right-hand generator rule applies here. Never seen yours before!

[@PhysicsHigh]

The palm rules I used is more common in school here. See my video on hand rules. It will explain that as well as Fleming’s.

[@mundymorningreport3137]

Beef up the demo by connecting two N poles of two magnets together and drop them through the plastic tube (or without a tube) and watch it fall slower than two magnets n-s to n-s. Not really Lenz's law, but putting Galileo to shame. Party on dudes, be good to each other.

[@hamzamaqsood374]

WHY IS THERE UPWARD MOTION OF TUBE WHEN IT IS STATIONARY

[@tamarapaterson9009]

The tube is moving upward relative to the magnet. If you imagine that you are on the magnet, the tube appears to be moving upwards relative to you. Hope that helps.

[@mshajahan6228]

Can u pls expln hw we can reduseEddy curnt nd why shd we refduse it?

[@PhysicsHigh]

We use eddy current in magnetic braking.

[@robertbeed497]

Surely a magnet dropping through a metal tube is acting as a generator and therefore the Right Hand Rule should be used.

[@mattenmedia]

I get confused about the left and right hand rules. Because you used both hands in this video relating to lenz's law.

[@PhysicsHigh]

Yes. There are two forms out there. The palm rule and Fleming. Trick is, use one and stick to it. See my video on hand rules.

[@charlieobrien8590]

But you used both on your video?

[@vinodsonawane1300]

This is because that the earths gravitational force, downwards is more as compared to the magnetic flux creating magnetism......

[@ft8925]

Right hand rule I think ?

[@PhysicsHigh]

If you are referring to Fleming’s right hand rule then yes, but I am using a different rule , the palm rule. Have video that discusses the different hand rules.

[@jeremyz8020]

Wrong explanation, left thank for or induction but you rust use right hand to find current first

[@jeremylindsay1682]

5:34 Similarlarly

[@pakistanmurdabaad1382]

over he.... over dee

[@artificiallift9110]

He probably speaks better English than you nobhead

[@bobbob123ful]

Artificial Lift That's prejudice

[@o.w.dobbins6927]

"I Did Not Know That".

[@notSavant]

The left hand rule is wrongly applied!

[@PhysicsHigh]

Different left hand rule

[@an_conner]

Can you please provide the reference for the left hand rule that you applied?

[@an_conner]

@@PhysicsHigh Reference please

[@polymetric2614]

the magnetic field over hee

[@jefferyaustin1571]

What is over he? who is over he?

[@PhysicsHigh]

Haha. Not American

[@Fishies125]

Chube.

[@PhysicsHigh]

+Jon Russell you making fun of how I say "tube"? You must be American. 😜

[@lebergerdesphotons4565]

It couldn't happen that you get more out than you put in IF it's truly a closed system. Not surprisingly, you, having been raised in the dogma of believing that you have closed systems will only see what you have been programmed to see. What is your proof that you have a closed system here? Doesn't this mean that you are denying the existence of the zero point field? Or are you implying without proving that you know that nothing you can do would ever interact with any part of the zero point field? If so, how do you know that? Have you proved that? Proving a negative is quite difficult, I doubt you have. So you are good for a reference in the fictionaly world of closed systems. That is what I came here to learn, so I could see the difference between the effects of closed systems and the real world of which you are in complete denial. Thanks for that. By the way, your grandparents did not participate in a shoah. They participated only in the mass imprisonment, total confiscation of property and exploitation of the labor of your chosen targets. So forgive yourselves and please resume some of the critical thinking which we haven't seen so much of since the time of Lenz.

[@bottledducky9610]

this video saved me from crying so many tears, tysm 🥲❤‍🔥

[@davidcorbett2170]

Excellent explanation, thank you