One good way to make a dramatic experiment is to get two identical
Neodymium-Iron-Boron magnets, permanently demagnetize one by
subjecting it to heat, and comparing how they perform in the copper
pipe. You could look up the demagnetizing temperature[1] and rig up
a thermometer, but it's easier to hold a small compass near the
magnet as you heat it. You could also try degaussing it with a
powerful AC electromagnet.

[1] See irreversible demagnetization versus temperature curves
at http://www.component.tdk.com/eneor_mg.pdf

Also see:
http://www.scitoys.com/scitoys/scito...s/magnets.html
http://www.rare-earth-magnets.com/ma...agnets_FAQ.htm


--
Guy Macon, Electronics Engineer & Project Manager for hire.
Remember Doc Brown from the _Back to the Future_ movies? Do you
have an "impossible" engineering project that only someone like
Doc Brown can solve? My resume is at http://www.guymacon.com/