Is this a special effect or are MAGNETS FREAKING AWESOME?????

[NYC_SKP]

I love these magnets and just this weekend I saw the clip posted below linked in a "Make Magazine" article.

A Neodymium Magnet dropping through a thick-wall copper tube falls VERY SLOWLY.... So I got some pipe and have been amazing everyone at school!!!

Actually, I am looking for a thicker copper tube like what is used in this demonstration. Observe:

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[Graybeard]

1. Way cool.

.
.
.Why do it do dat?
.
.

[siligut]

3. Copper is weakly magnetic

At least that is the only reason I can imagine.

[tclambert]

12. Part of what makes it cool is that explanation is completely wrong.

A moving magnet creates electrical "eddy" currents in the copper. Those eddy currents then create an electromagnetic field opposite to the original magnetic field.

[siligut]

14. That is really cool

So gravity makes the magnet move and it is the movement that causes the reaction? That is so cool, thank you for explaining it so neatly and clearly.

[NYC_SKP]

4. The magnet passing by the copper creates an electromagnetic field ahead of itself....

...which actually REPELS the magnet; slows it's passage down.

It's really paradoxical, and COOL!

[caraher]

5. Counterintuitive but not at all paradoxical

Essentially, the eddy currents induced in the copper create a magnetic field directed opposite that of the falling magnet. I use a really long tube demonstrating this in classes.

Here's a really remarkable demonstration of the same basic effect (this time with a stationary magnet):

Yeah, it still seems like magic even when you know the physics!

[NYC_SKP]

6. Very cool! (nt)

[jonthebru]

8. Great name for a rock band

Perforated pendulum

[freshwest]

9. I got magnets for my kid to play with. Just loved them. Also took speaker magnets for play, too.

We're all electric beings of light, or something like it.

[eppur_se_muova]

10. A consequence of Lenz's law ...

http://en.wikipedia.org/wiki/Lenz's_law

also responsible for electromagnetic rail guns.

[Suich]

2. That's REALLY cool!

[chollybocker]

7. And it never fails.

Theme parks should make rides outta this stuff.

[tclambert]

11. Some newer roller coasters use this effect for braking.

Also high speed trains make use of it. http://en.wikipedia.org/wiki/Linear_eddy_current_brake#Linear_eddy_current_brake

[jakeXT]

13. Doesn't really work with non Neodymium ones

Maybe when they are light and have a hole

[NYC_SKP]

15. Yes, actually, it does.

It is slightly less effective with the black rare earth magnets, but seems to work best with plated neodymium.

Thickness of the copper, however, is everything here.

Even a loose fitting 3/4" within a 1" schedule L Home Depot fit is slower than the 3/"4 inch alone, so I can't wait to get some heavy 1/4" wall tube, or thicker.

[jakeXT]

17. I noticed it's working better when you stack the magnets and the height of the magnetic object

increases.

Still, I haver never seen a neodymium magnet.

[NYC_SKP]

20. In experiments, I've found an ideal range...

In stacking magnets, beyond a height of about 1.5 x diameter the effect diminishes.

Also, I've used square and rectangular shape magnets, too.

I imagine an ideal magnet would be hollow core and 1.5 x diameter in height.

Wall thickness is where I get a lot of improvement.

[northoftheborder]

16. This is all so fascinating to me. I'm not educated in it, but it's still interesting.

[intaglio]

18. Notice, then the magnet is put in the tube

The guy spins it, just a flick of the fingers but a spin nevertheless ...

[Fantastic Anarchist]

19. Trippy!

Dig the pic, too, of the alien guy. He trips me out.

[dawg]

21. I am so very sorry.