Magnetic levitation

Maglev train

When we talk about magnetic levitation what we are referring to is an object suspended by magnetic pressure which counteracts the effects of gravity. It generates images of large futuristic objects hovering and travelling at high-speeds.

However, magnetic levitation is more science-fact than science-fiction as magnetic levitation is now used in super-high speed trains and magnetic bearings as well as for cool desktop displays that can amaze your friends and family!

From a young age we are all taught that the opposite poles of a magnet attract and the identical poles of a magnet repel. So, surely you could just use two large, strong magnets set to repel and one will levitate above the other.

Unfortunately, magnetic levitation is not quite so simple. This is because strong magnets don’t like being in repulsion with one another, they will do everything possible to flip over so their opposite poles are attracting and snap together. If your fingers are in between, it can be a very painful and messy experience!

If you do have two large magnets and you can keep them from flipping over, by putting a non-magnetic pole through the middle of them for example, you can demonstrate how magnetic repulsion works, like in this video – super-strong magnets levitating a man.

An alternative and more spectacular method to achieve levitation is by using strong permanent magnets and diamagnetic material.

Most common materials are diamagnetic including, water, wood, copper, silver, gold, plastic, DNA the list goes on. Diamagnetic materials repel and are repelled by strong, external magnetic fields like those produced by neodymium magnets or electromagnets. They do this because the orbit of the electrons that surround their atoms change to create a weak magnetic field in repulsion to the magnetic field that is applied to it.

 

There are a number of methods for demonstrating diamagnetic levitation in action:

Placing a diamagnetic object in a strong electromagnetic field

OK, many of us will have seen the gobsmacking image of a levitating frog. This was achievable because a frog has low density and is made primarily of water (which is diamagnetic), and, because a huge electromagnetic field (16 Teslas around 20 times stronger than the strongest magnets) was used. The stable electromagnetic field keeps the frog in place and these experiments have been used to determine the effects of weightlessness on living things. The frog was unharmed…

 

Using a superconductor to repel strong magnets (or vice versa)

Superconductors are materials that when cooled to incredibly low temperatures (around -200oC) have no electrical resistance and because of this they repel magnetic fields. They are the perfect diamagnets because of currents that flow at the surface of the superconducting material which generate a magnetic field that exactly cancels out that of an externally applied magnetic field such as that produced by strong permanent magnets.

We found this video online that shows superconducting material being repelled by a track of strong neodymium magnets – please don’t try this at home as the superconductors are cooled using liquid nitrogen, which is very dangerous!

 

Hovering diamagnetic material above strong magnets

As super-strong permanent magnets are now readily available it is possible to use them to levitate small pieces of the most diamagnetic materials such as pyrolytic graphite and bismuth. However, even in these materials the diamagnetic affect is extremely weak. An arrangement of strong neodymium cube magnets are typically used to float small, light pieces of graphite. The magnets need to be aligned with alternating poles facing upwards, if you arrange them differently the graphite will not float. With this approach you can create a fascinating display to amaze your friends and family.

 

Hovering a small neodymium magnet between diamagnetic material

The final and best way to replicate magnetic levitation with a DIY home experiment is to levitate a small neodymium magnet between two diamagnetic blocks. For this, you need a magnet such as a 23mm diameter x 20mm thick N42 neodymium magnet or similar to act as the lifting magnet which counteract the forces of gravity, a couple of carbon-graphite blocks, a small neodymium magnet such as a 3mm3 neodymium magnet for levitating and a wooden stand. The key to making the arrangement work is fine adjustment and patience. We found this video showing how all the parts can be put together to create a fabulous display.

Hope you found this article useful, if so, please leave us a comment and good luck in creating your magnetic levitation devices!

 

About Matt Newby

Matt Newby is part of a group of people that have a passion for magnets and their endless possibilities. As part of the marketing team at first4magnets.com Matt's aim is to create great magnet-related technical content and help people understand how magnets can be used.

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