Flywheel/Encoder patterns

[Chris Howard]

At 15:33 12/8/96 -0800, you wrote:

>	Pardon my ignorance, but what effect does a magnet have on a non
>metallic element like aluminum or copper.
>	How's it work?
>	And what kind of drag can you expect from such a device?
>

I'll presume you know that aluminium and copper are metals and you in fact
meant non-ferrous elements. :)

Here's what I remember from physics lectures:

Faraday's law states that a changing magnetic field will induce an emf in a
conductor. If the conductor forms a circuit, a current will flow. This is
how a generator works.

                |  ________
                | | Magnet
                | |________
                |                        (ascii amateur)
 ---------------|
                |
                |
                |

Consider a metal disk which is rotating on a shaft with a magnet at right
angles to the disk on one side. The disk will experience a changing
magnetic field and hence an emf will be induced in it. There are of course
many paths for current to flow within the disk as it is a conductor.
Circular currents flow in the disk and, due to the finite resistance of the
metal, energy is dissipated as heat. The kinetic energy of the disk is
changed to heat energy and the disk slows down.


EMF = electromotive force (V)

Hope this helps,



Chris Howard
Computer Science
University of New South Wales
email: s2184002 at cse.unsw.edu.au
Web: http://www.usyd.edu.au/~choward - Aussie Touring Car Action

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