Gravity is Optional
Magnetic Repulsion

Magnetically speaking, materials are classified as This page is about diamagnetism. On youtube everyone cares about diamagnetic levitation. (Really cool.) However, except for a few videos below, I concentrate on experiments that most people can do at home (assuming that you have about $10 in magnets.)

Levitating a Sheet of Carbon | The Frog | Torsion Pendulum

Levitating a Sheet of Carbon

This is much better than any video I could make.

How To Float A Piece Of Graphite On Magnets

He uses both 1/4" N42 cube magnets and 1/8" N50 cube magnets.

He says that rectangular and circular magnets will not work.

The Frog

Unbelievable - a frog suspended in a magnetic field.

This is possible because both water and carbon are diamagnetic - repulsed by a magnet. For more information, see The Frog That Learned to Fly.

Torsion Pendulum

"Everyone" does pyrolytic carbon levitation (boring .. well almost) .. and I don't have enough money to levitate a frog (darn) .. but I had a strong cylindrical magnet I drop down copper tubes and I wanted to see what I could accomplish with what I had.

I remembered the Cavendish Balance (1783 AD) from physics - this is what was used to measure the gravitational constant. Basically, it is a torsion pendulum which allows the measurement of very weak forces. I figured, what the heck, I would make one and try to see if I could use it to detect diamagnetism .. and it worked.

First I used pencil leads - the kind used to refill mechanical pencils. Then I tried a piece of wood .. a stick from outside, then a match stick. They all worked. Eventually, I tried a piece of chalk and a lego piece - they also worked.

Flash video goes here

I also had a few notable failures


To make a pendulum, all you need is a support and some sewing thread. For a support, I just used some bamboo skewers (a couple of dollars at any grocery store). I initially used 3 skewers like an Indian teepee. However, this was unstable (kept falling over) so I use 4. A rubber band was used to hold them together and to attach the thread.

I tried just putting a loop in the thread to support the lead .. but that was very hard to balance. I now use a spreader and 2 vertical loops .. much easier. Be sure to make the loops large enough so that the magnet affects the object placed in them and not the wooden spreader .. I use about an inch.

They say that bismuth is a better diamagnet than anything else on the planet. Well, that may be true, but my experience is that pencil leads are pretty good. I obtained 2 samples of bismuth hopper crystals at a local rock and mineral show. My original plan was to melt them down and make a bismuth rod. However, being basically lazy, I decided to simply tie them to a long stick and see what happens. As luck would have it, this was the first stick I tried that was not repelled by a magnet. Perhaps this is because it was collected in winter. (It was very light and probably dry.) Because the crystals were different sizes the balance point was closer to the larger crystal.

Well, it worked .. but I was not impressed. The pencil leads were much better.

Author: Robert Clemenzi
URL: http:// / Magnetic_repulsion.html