Cool experiments with magnets
I've had my share of playing with iron filings and magnets, trying to stick magnets together the wrong way, or pulling around piles of bolts with a big magnet. I'm sure my kids will too (in fact I've been saving iron filings from cutting rebar), but in an old issue of Home Power
they were talking about a presentation given at a workshop on building wind power generators, there the guys at Wonder Magnet
gave a presentation on cool things to do with magnets, like dropping them down a copper pipe which generates a counter magnet field and actually breaks the fall. They also have this cool stuff called ferrofluid
Basically this is an oil with magnetic particles in it. In the presence of another magnet, they take the form of the magnetic field in 3D. Adult supervision required however, as it will make a major mess if spilled (stains skin, clothing, table tops, etc.)
Something to add to my chrismas wish list.