Bismuth and Carbon-Graphite work about equally well for this experiment, but Carbon-Graphite is by far the easiest way to go. We tried Bismuth first--we had to melt down Bismuth pellets that were intended as an alternative to lead for re-loading shotgun shells, and cast them into small ingots. Since it's so much easier to obtain and work with, our recent experiments have been exclusively with Carbon-Graphite. You will also need a Neodymium Iron Boron rare earth magnet in the strongest grade possible (try our Item #24, an N-45 grade 3/16 inch gold-plated cube magnet) and a large magnet to use overhead; this could be a stack of ceramic magnets. Speaker magnets would work. We used NdFeB rare earth magnets overhead--this gives a range of 4 to 6 inches above the small levitating magnet. Ceramic overhead magnets give a distance range of around or 3 inches...but are much, much cheaper. The height of the magnets overhead will need to be adjustable, as the distance is critical. In our demonstration the overhead magnets are glued to a threaded shaft so that they can be raised and lowered. On the bottom of the assembly, 1 or 2 diamagnetic plates are required. If two plates are used, the distance between them can be adjusted to achieve maximum levitation. In our demo we used pennies as spacers with good results.
Here are some pictures of various magnets that we used in our experiments:
Levitating magnets requires very precise adjustments, especially when using only one plate. If you get the top magnets too close, the levitating magnet will take its final leap upward and usually shatter when it collides with the large magnets above.
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