What you're seeing here is a neodynium magnet
falling through a copper tube
, though it falls very slowly for as long as it is in the tube. Since the magnet is moving within the copper tube, an electric current
is formed. With the formation of this electric current, a magnetic field is also formed that starts to attract the magnet.
The magnet falls straight through the tube without attaching to the inside of the tube because the electric current and magnetic field that are being made are equally distributed within the tube. This means that the magnet feels equally attractive forces from all directions, so it doesn't stick to just one area inside the tube.
The magnetic field within the copper tube does slow the magnet's fall but it wouldn't stop the magnet from falling all the way through. This is because without having the magnet moving inside the tube, there wouldn't be any electric current (Eddy Current
), which would also result in the lack of any magnetic field, causing the magnet to start falling again. While the magnet is inside the copper tube, even though it is falling and not physically attached to the insides of the tube, the tube as a whole will feel heavier. The total mass of the system doesn't change, but the weight does.
The Eddy current inducing effect that the neodynium magnet has mainly has to do with Lenz's Law
. Wikipedia describes Lenz's law as, "An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux." It's an explanation to how electromagnets follow Newton's 3rd Law
and the Law of Conservation of Energy
Videos of the experiment and a short explanation of Lenz's law here: http://www.geekosystem.com/neodymium-magnets-copper-pipes/
Short YouTube video of what's going on here: Copper Pipe Magnet
Same YouTube video with an explanation of the demonstration: http://www.neatorama.com/2011/08/09/neodynium-magnets-fall-slowly-through-copper-pipe/#!Aa9wQ