Physics Demo -- Lenz's Law

[zarkoasenov]

If you connect a lamp to section of the tube, phase and zero higher conductivity than the tube, does the magnet fall faster when passing this section?

[SpazzyMcGee1337]

My Phy 110 professor did this in class. I was amazed!

I love all these cool physics experiments!

[davidls11]

It's not eddy currents...the aluminum tube is longer on the inside than it is on the outside. 

[GregoMorgan]

@davidls11 You got me thinking a lot.

[davidls11]

@GregoMorgan Doctor Who reference.

[freemanx2x]

Many people believe that the magnet in motion creates a field that opposes the magnets own filed. Like if you approach a magnet with the N pole to a conductor plate the induced current in the plate will develop an opposing N pole. Its not like that! The induced field will oppose to the VARIATION of the inductor field wich is completly different thing! The induced current will have the same orientation with the current in an DC electromagnet used insted of a permanent magnet in the above example.

[jj987987987]

can elevator use that method?

[panzarw]

lemme try: The magnet falls in the metal pipe thus creating current in it and if theres current there an electric field which try's to repel the magnet.

I'm right ?

[gennaman2bit]

@panzarw yes, u are. A magnetic field variation in a conductor produces a current which produces a magnetic field, and as Lenz says "An induced current is always in such a direction as to oppose the motion or change causing it".

The current produces also a thermal change due to joule law (e=current^2 * resistance * time).

In a superconductor pipe there is no resistance at all, so the current induced by Lenz law will never dissipate, so the magnet never falls.

[PacVsEu]

This is not lenz's law, this is an Eddy current, which is a reverberation of a magnetic field through a on-ferromagnetic metal. Lenz's law is a similar effect, but involves and polarity rotational electromagnetic field, which, coupled with eddy currents forces the coil to levitate.

[gennaman2bit]

@PacVsEu Eddy current is due to lenz law, and as the video shows, u don't need to have rotational field to see it. Eddy current is the effect of Lenz law, that's it.

[quidproquo2004]

I love physics <3

[tenchimuyo69]

Obvious shit is obvious.

[Casowsky]

The slow magnet is just like 'oh... oh hey guys ! Whad I miss?'

[m1ndcontroller]

Oh my God?  It's a miracle!!! MIT finally demostrated something correctly!!!!

I didn't think it was possible.

[onthecuttingedge2005]

does it work with conductive glass?

[super6plx]

@onthecuttingedge2005 yes, anything that's conductive

[firewilson81]

does it make a difference for the rate of speed the magnet in the metal tube falls if the poles of the magnet have the south or north facing either direction. like since the south is entrance and the north exit for the atoms, (yes?) doesn't this mean if the south is pointed down it will fall faster then if north faces down? fractions of seconds, that is?

[LanceTheBlueKnight]

Magnetism isn't a transfer of atoms.

Think of it as gravity... it's not a thing we can touch.. there's no atoms pulling on us physically. It's a field, just like a magnetic field. So no, the orientation of the magnet wouldn't have an effect.

[andrewwingard]

it would not matter because lenzes law just states that when the magnet is droped regardles of the direction, there will be a created field that opposes the magnet be it positive or negative.

[terryphi]

is there a way you could use the same principle to speed it up?

[LanceTheBlueKnight]

That's what a railgun is.

[adisharr]

Looking to build an over-unity motor? ;)

[RayJoel2007]

very sharp ;-)

[domthomson]

@terryphi sadly we physicists did think of that and, as it turns out, no. Lenz's Law effectively opposes any change, gravity tries to speed it up, lenz's law slows it down

[Jynna28]

Great demo.

[megahurtz30]

pretty cool demonstration! Simple and instructive.