FUN WITH DIAMAGNETIC LEVITATION
Earnshaw's theorem from 1842 states that the stable levitation of a permanent magnet is
impossible without an added force for stabilization. This can be demonstrated with a stack of ring magnets--unless
they have a stick through the center, they will flip over instead of levitating.
However, the phenomenon of diamagnetism can provide the stabilizing force needed for levitation without any
sort of stick or tether.
Click on each photo for details on how to reproduce the experiment!
The photos above show three variations of the diamagnetic levitation experiment--a magnet
levitating between Carbon-Graphite plates, a magnet levitating between Bismuth plates, and a chip
of Carbon-Graphite levitating over magnets.
What is Diamagnetism?
Certain materials are diamagnetic, which means that when they are
exposed to a magnetic field, they induce a weak magnetic field in the opposite
direction--their magnetic susceptibility is negative.
Diamagnetic materials include Carbon-Graphite, water, protein, DNA, wood,
Bismuth, Silver, Diamond and Gold. Bismuth and Carbon-Graphite are the strongest, around 20
times more diamagnetic than water. With an extremely powerful electromagnet, it's possible
to diamagnetically levitate a living creature due to the water, protein, and DNA in it's body.
See a levitating frog here!
There are a few easy experiments that demonstrate the diamagnetic properties of water. A drop of water
could be levitated with a strong enough magnetic field--this has been done with large electromagnets, but not
yet with permanent magnets.
Check out our diamagnetic
water experiments page HERE. Superconductors are perfectly diamagnetic--that's part of why the demonstration of magnet levitation
over a superconductor is so dramatic.
Check out our superconductor levitation page HERE.
How does Diamagnetic Levitation Work?
A large magnet above the small levitating magnet provides a lifting force to counteract gravity. The
tiny, super-powerful levitating magnet is stable horizontally (it tries to stay centered in the big
magnet's field) but unstable vertically--it tries to fly up and destroy itself on the big lifter
magnet. The diamagnetic material provides vertical stability using the weak, reverse magnetic field
that is induced in it by the small magnet. With gravity compensated for by the big magnet, the diamagnetic
effect is enough to levitate the magnet. The effect will also work in reverse...the small levitating magnet can be suspended
underneath a diamagnetic block. This can be done using your fingers as the diamagnetic material (though
it is a bit tricky)--but please use caution around strong magnets or you'll get pinched.
What Materials are Needed?
We sell all of the materials needed to reproduce these experiments on our
Large lifting magnet--We used a large Neodymium-Iron-Boron magnet for our stand. It works
at a distance of 4 to 6 inches above the carbon-graphite block. A stack of ceramic magnets
(such as speaker magnets) will also work, though they will have to be closer to
the levitating magnet than when using a N-I-B magnet as a lifter. Ceramics are also more affordable. Check our
Products page for availability of large
ceramic or Neodymium magnets, or call/email us. When levitating carbon-graphite over magnets, the
lifter magnet is not needed...one of the advantages of that method!
Small levitating magnet--Use the highest grade of N-I-B magnet available. We have successfully
levitated many different shapes of magnet, but the stronger the magnet,
the higher levitation you will achieve. We obtained great results with our Item #24( an N-45
grade 3/16 inch gold-plated cube magnet),
Item #49 (a 3/32 inch cube), and other discs and cubes of similar (or smaller) size. Use N-45 grade for best results.
Diamagnetic Material--Carbon-Graphite is the best material to try. It is possible
to get it from old DC motor brushes, but the material varies in how diamagnetic it is...some
samples will work batter than others, and some kinds won't work at all. Our Carbon-Graphite
proven to be very diamagnetic; it's what we used in all of our photos. Bismuth also works, but
is much harder to come by. You'll probably have to buy Bismuth shotgun pellets, carefully melt
them down, and cast them into ingots. That's why we've been using only Carbon-Graphite for our
recent experiments--you don't have to go through the long process of melting it down and casting it.
Levitation Apparatus--The adjustments needed to achieve stable levitation are very fine, and
the lifting magnet must be slowly and precisely lowered over the levitating magnet and Carbon-
Graphite. It should be fastened to a threaded shaft, which can be normal steel threaded rod. The
stand itself must be made of wood or other non-ferromagnetic material. The adjustment shaft for the
second diamagnetic top plate cannot be ferromagnetic; we used a slip-fit on wood since
brass threaded rod is so expensive and hard to find.
Also see our SUPERCONDUCTIVITY EXPERIMENTS!
An AMAZING diamagnetic levitation page--they inspired us to experiment with all of this stuff
Another great diamagnetic levitation site
More diamagnetic levitation experiments
Our Shopping Cart (Get your magnets and Carbon-Graphite here!)
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2606 West Vine Dr.
Fort Collins, CO 80521