Leader Resource 1A 1 Continued
The first thing that you will need is a rare earth magnet, preferably a neodymium disk magnet. For this and most other purposes, the most efficient magnet geometry is where the thickness is comparable to the diameter. That magnet that I used was part number ZD4 from K & J Magnetics, it's one inch in diameter by a quarter-inch thick, and made of N48 grade (strong) neodymium-iron-boron, and cost about $5. (Note that hard drive magnets are usually not useful for making a compass because they will have both poles on the same face of the magnet.
To make a floating magnet we'll need some other things: A tub of water, a foam tray, a knife, and a permanent marker. Keep the magnet separated from the knife.
1. Using the knife, make a slit in the foam tray.
2. Shove the magnet into the slit. It should seat firmly in place.
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