, , , ,

Check out this awesome video of neodymium magnets slowing their own fall through a copper tube with shear magnetic muscle, then stick around for the science.


Neodymium Magnets

A neodymium magnet (also known as NdFeB, NIB, or Neo magnet), the most widely used type of rare-earth magnet, is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. Developed in 1982 by General Motors and Sumitomo Special Metals, neodymium magnets are the strongest type of permanent magnet made. They have replaced other types of magnet in the many applications in modern products that require strong permanent magnets, such as motors in cordless tools, hard disk drives, and magnetic fasteners [1].

Neodymium magnets are very very strong. Their magnetic field strength can be as much as 1.4 Tesla’s. For perspective, the strongest recordings of the Earth’s magnetic field are around 65,000 nano-Tesla’s (a value of field strength). This means that a neodymium magnet is around 21,500 times stronger than the Earth’s magnetic field.

Falling Magnet Science

As the magnet falls through the tube, as it does in the videos above, its magnetic field creates an electrical current in the copper tube. English physicist Michael Faraday discovered this, that a changing magnetic field (flux) leads to a flow of electric charge or current.

Physics tells us that where there is an electrical current, there is also a magnetic field. This new induced (or created) current’s magnetic field opposes the original magnetic field of the falling magnet.

This magnetic field (green) from the induced current (red) created by the falling magnet opposes the motion of the magnet, slowing it down.

At each point the magnetic passes, there is an induced current above and below the falling magnet, meaning that there are also induced magnetic fields pulling the magnetic from above and pushing the magnet from below. Combine all of this and you have a magnet falling much slower than plain old gravity would normally dictate.

If visualization is more your thing, try watching this video:

or looking at this physics GIF’s.

Still confused? You can find another discussion of this phenomenon here.

See? It’s not always lab coats and test tubes. Many times, science looks like downright magic.

About these ads