Magnetic Levitation

Magnetic levitation seems like magic to most people, even though the concept has been around for ages. Maglev trains utilize a strong magnetic field in the rail to suspend a train using the forces of repulsion.

Image courtesy of FYS

Powerful rare-earth neodymium magnets are found in hard disks, CD-rom drives and speakers.

But you still need to know where to look. They'll be pretty darn obvious in an old hard disk (may need a hammer to bust it open), but in a CD-drive you have to completely dismantle the optical mechanisms PEACEFULLY (don't go smashing with a hammer). They can be very hard to get out of speakers though. Patience is your friend here.

Some metals are attracted by both poles of a magnet. The most popular one is probably Iron. However, there's another group of metals, which have a property called diamagnetism. Materials such as bismuth, carbon, graphite and aluminium possess this weird property.

Basically diamagnetic materials naturally very slightly repel both poles of a magnet due to complex reasons.

The idea behind diamagnetic levitation in the lab is to levitate a small, but very powerful neodymium magnet between two layers of diamagnetic material. This is done by attracting the small magnet using a larger one above the top piece of diamagnetic material. As the big magnet pulls the small one up, there comes a height which the small magnet has enough force to overcome gravity, but not enough to overcome the additional repelling forces posed by the top piece of diamagnetic material. Thus it seems to hover in mid air.

Although bismuth is by far the best material and provides the best results, it is relatively expensive and limited. I'll be getting some soon though, but for the mean time... aluminium will have to do. It sucks, but it works.

Here's the setup in real life. Compare to the above diagram to see the similarities.

And.... results! Hovering a mere fraction of a millimeter above and below the aluminium disks.

Now here is possibly the easiest, fastest, and cheapest form of magnetic "levitation" ever!

The ring magnets in the photo are magnets from a dismantled magnetron. These are found within microwave ovens, and can be a bit tricky to extract sometimes. If you do go looking for these, they can be found in-between the magnetron cooling fins. A hammer is useful for doing the hard work, provided you don't go SMASHING your way through (which I have done countless times, ruining several magnets).

These magnetron magnets have less power density as compared to the neodymium magnets, but still pack alot of punch.

Here is a close up of the simple maglev setup. A PVC pipe of suitable diameter is simply placed into the rings of a few magnets, and these serve as the base.

Another magnet is placed through the PVC pipe, with the north pole pointing down if the north pole of the base stack is pointing up, and vice versa.

Note that the field is not perfectly balanced, as the "levitating" magnet is on an angle. If the PVC pipe wasn't there, it would just flip over and snap straight onto the base magnets, and you would probably end up with shards of magnet all over the floor.

Video time!

Click HERE to watch what happens when the magnet is dropped from the top of the pipe. (350kb WMV)

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Or... using only two magnets as a base, the rest of them can be suspended in a S-(NS)-(SN)-(NS)..etc configuration, so that all magnets repel each other.

The width of the gaps between the magnets seem to follow some sort of exponential trend, although there is a clearly a limiting factor as the top magnet cannot be suspended anymore than its repelling power allows it. The gaps are smaller towards the bottom, as the lowest magnet has to carry the weight of all the magnets above it.