Magnetic levitation is really fun to experiment with, and can make a great science fair project. However, it's hard to get dramatic results--the problem goes back to Earnshaw's theorem from 1842. He proved mathematically that any electrical or magnetic levitation would require an extra axis of stabilization...a force from a different direction.

You can show this with ring magnets. Put them on a stick, and they do indeed float over each other. However, the stick is required, that's your extra axis of stabilization--remove it, and the magnets simply flip over and jump to each other, no longer floating. The phenomenon of diamagnetism provides a simple, inexpensive solution to this problem and gives fairly dramatic results.

Most people are familiar with ferromagnetic materials--iron, steel and permanent magnets. These materials are attracted by magnetic fields, and can keep their magnetism after exposure to the field. Diamagnetic materials include carbon-graphite, water, protein, DNA, wood, bismuth, silver, diamond and gold. When exposed to a magnetic field, these materials induce a weak magnetic field in the opposite direction. Superconductors are perfectly diamagnetic, but require liquid nitrogen to work--not something that most folks have a jug of in their fridge!

Diamagnetism is the key to this experiment, and provides the extra stabilizing force needed. We'll be using carbon-graphite and bismuth because they have the strongest diamagnetic effect.

Step 1: Materials Needed

This entire project should cost you less than US$20. You may not be able to find all of them locally, but I've provided links and Google search suggestions for any that you might have to order off the internet.

carbon-graphite blocks, 1.5 inches square by 1/4 inch thick, quantity 2 -- carbon-graphite is commonly used in motor and alternator brushes. However, these are generally too small, and some samples are more diamagnetic than others. It's best to look for 'pyrolytic' carbon-graphite, or for samples that are known to be highly diamagnetic by the seller. They should cost under US$7 each.

small rare-earth magnet to levitate -- This magnet should be of neodymium-iron-boron (NdFeB) composition and of at least N40 grade. Cube or disc shapes work well. This magnet should be very small for best results--the one we will use here for the demonstration is a 1/8 inch cube of N40 grade. These magnets cost less than US$1 each.

large magnet for lifting -- This magnet counteracts the force of gravity to allow the week diamagnetic force to work, and does not have to be very powerful. We used a 1.5 inch diameter by 3/4 inch thick ferrite (ceramic) disc magnet, which cost about US$2.

experiment stand -- we built ours out of wood, but it could be as simple as playing cards stacked over platic cassette tape cases. The key here is fine adjustment -- the threaded rod allows very fine adjustments of the distance between the lifting magnet and the graphite plates.
Hey nice tutorial but.. one question.. Can the temperature variations affect it?
You can buy them online. That is the best resource. try something like Ebay. Or you can also find raw copper from junk yard and then melt it in your back yard. Keep in mind that Bismuth gives the best result of all. I am also into this and currently in China. Here there is abundance of Bismuth so i will try with bismuth or graphite. Copper slabs are expensive here and i dont have a backyard :)
Is there anywhere that you can just locally go out and buy the carbon-graphite blocks. I need it fast this week. btw, i live in fremont, ca if that helps.<br /> <br /> -thnx
hey.. i want dose... where do u live?? i m frm india.. did d project wrkd??? i wanna make it within a week or so..
<a rel="nofollow" href="http://www.scitoys.com">scitoys.com</a>I made one of these from Scitoys.com, except instead of graphite I used Bismusth and melted it into disks. <em><strong>Its awesome!</strong></em> <br/>
that is my second favoritwe website<br />
hey man scitoys is really fooling u all the crap available there is damn expensive the laser pointer that they sell for 11$ is actually availaible for 0.6$
where can i get the graphite?
he said carbon twice...
i have a magnet from a broken harddrive damn that thing is powerful!
this is realy close to this web site www.scitoys.com
It was back in 2002 when we first tried this experiment and put up our web page about it. We were trying to maximize the levitation we could get (and were trying to make the CG chips float over the magnets). We exchanged lots of information with Simon from scitoys.com trying to make it all work; he's a good guy and will treat you right if you order from him. His business was just getting started back then too. DAN
ya ive ordered a lot of magnets off of him and hes realy good about getting it shipped =D<br/>
Can the rig be flipped over? Rather than using the large magnet to lift the small magnet, can it be placed below to repel it?
That's possible, but I've never tried it. It's probably easier to make the carbon graphite chip float over magnets, as shown in step 6. Give it a try! DAN
OOOOOOOOOOOOOOOOOO floating aaaaaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhhh cool
i like magnets : ) i'll have to take my old neodymium headphones apart to get at the magnets
Thanks for the feedback, folks. I'm glad that putting my link on only the last page was subtle enough that folks didn't think it to be shameless self-promotion. Trebuchet -- ferrofluid would only be affected by the lifting magnet, not the diamagnetism. Ditto the tiny magnet, it would just get covered with glop. Stay tuned for some fun with ferrofluid, though--heh heh. Now that I have a camera that can shoot reasonable video, I'm going to put some stuff together on ferrofluid. It really dances to Jimi Hendrix.....
the part that impressed me most is the fact that you WORK for a company that sells all the materials to make this project...but you never linked to any of them with your own company...shows where your dedication is...to the science...not the wallet..deffinitely hard to find now adays...deffinite props! very well writen and excellent explanations...
I'm really glad you posted the last step..... There have been a few members in the past that ripped this pictures just to be "first" without even doing the experiment... What's even funnier is when they didn't know the principle and tried to pass it off as just anything magnetic :P Out of curiosity and a luck of funds to try myself.... what would ferro fluid look like in there?

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