- #1
Jon.Nevermind
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Help me explain how the "magnet dropped down a copper tube" demo conserves energy
I've tried explaining to this person that the potential energy you give a magnet when you do work against gravity to raise it up to the copper tube is all the energy it has to deal with, and once dropped down it, natural laws (Ampere's, Lenz's etc) governing the situation so happen to create a series of eddy currents, fields, and forces which oppose its descent. The magnet moves down the tube slower, heats up the pipe, and imparts some momentum to it as well. The heat cannot exceed the potential energy you give the magnet in the first place.
I tried thinking of the simplest analogy possible, and came up with: http://www.google.com/images?q=koos...source=og&sa=N&hl=en&tab=wi&biw=1280&bih=939" correctly sized and dropped down the tube would slow down, heat up, and impart some momentum to the tube, but we don't think it "creates energy" because...it's a koosh ball...and its tendrils are plainly visible.
He doesn't like this analogy because friction will eventually wear the koosh tendrils down, but "not so with a permanent magnet".
Now, I know exposing permanent magnets to opposing fields can (somewhat) disassociate electrons in its magnetic domains, but will performing the magnet drop/copper tube demo enough times analogously wear down the magnet? Or is this just not a good analogy in the first place?
If that's not a good analogy, most basically, there is a sum resistive force acting for the distance of a magnet's fall through a tube that doesn't exist with a normal ball.
How better do you explain to a layperson that it's not "energy out of nowhere"?
I'm trying to create the argument to show at the end "you can't get something from nothing; energy conservation works", so I don't want to use that as a supporting argument.
I know it sounds silly.
Anyone?
(Thank you whichever mod for placing this in a more appropriate forum)
I've tried explaining to this person that the potential energy you give a magnet when you do work against gravity to raise it up to the copper tube is all the energy it has to deal with, and once dropped down it, natural laws (Ampere's, Lenz's etc) governing the situation so happen to create a series of eddy currents, fields, and forces which oppose its descent. The magnet moves down the tube slower, heats up the pipe, and imparts some momentum to it as well. The heat cannot exceed the potential energy you give the magnet in the first place.
I tried thinking of the simplest analogy possible, and came up with: http://www.google.com/images?q=koos...source=og&sa=N&hl=en&tab=wi&biw=1280&bih=939" correctly sized and dropped down the tube would slow down, heat up, and impart some momentum to the tube, but we don't think it "creates energy" because...it's a koosh ball...and its tendrils are plainly visible.
He doesn't like this analogy because friction will eventually wear the koosh tendrils down, but "not so with a permanent magnet".
Now, I know exposing permanent magnets to opposing fields can (somewhat) disassociate electrons in its magnetic domains, but will performing the magnet drop/copper tube demo enough times analogously wear down the magnet? Or is this just not a good analogy in the first place?
If that's not a good analogy, most basically, there is a sum resistive force acting for the distance of a magnet's fall through a tube that doesn't exist with a normal ball.
How better do you explain to a layperson that it's not "energy out of nowhere"?
I'm trying to create the argument to show at the end "you can't get something from nothing; energy conservation works", so I don't want to use that as a supporting argument.
I know it sounds silly.
Anyone?
(Thank you whichever mod for placing this in a more appropriate forum)
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