What Happens When You Drop A Magnet Inside A Copper Tube [video]
Yup, it's pretty cool. This was one of the most impressive demo's my physics professor did in our freshman physics class. The point is that as the magnet is falling through the copper tube it creates an electric current which then creates a magnetic field in the opposite direction of the magnet's movement. In other words, this is the practical application of the Right Hand Rule [1].<p>Two fun facts about it: first, if you cut a small notch along the length of the tube, this will not happen as the current cannot go around the tube.<p>Second, imagine a superconducting tube with an extremely powerful magnet right in the center of it. Now, try to get the magnet out without cutting the tube.<p>[1] <a href="http://en.wikipedia.org/wiki/Right-hand_rule" rel="nofollow">http://en.wikipedia.org/wiki/Right-hand_rule</a><p>Edit: Of course, there's nothing special about the tube being made of copper. Any conducting substance will do.