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.
Original link: <a href="https://www.youtube.com/watch?v=keMpUaoA3Tg" rel="nofollow">https://www.youtube.com/watch?v=keMpUaoA3Tg</a><p>This digg page is blogspam.
Lenz's Law in action, lots of good demos online, or take any strong magnet and move it rapidly while in close proximity to any non-magnetic conductor (brass, copper, aluminum, etc.) You can feel the force exerted by the generated field. Automobile speedometers used to operate on this principle.
Here is a much more informative video: <a href="http://www.youtube.com/watch?v=NqdOyxJZj0U" rel="nofollow">http://www.youtube.com/watch?v=NqdOyxJZj0U</a>
be very careful when handling such powerful magnets - if you have something metalic on you, they might jump off the table and smack you really hard. bones will be broken.
This effect gets used in modern trains and roller coasters in the form of linear eddy current brakes. In practice, this looks like an electromagnet that's held just over the rail.<p>More reading: <a href="http://en.wikipedia.org/wiki/Eddy_current_brake" rel="nofollow">http://en.wikipedia.org/wiki/Eddy_current_brake</a>
So it's ok to post links to third party instead of the original content now ?
here's the link to the video instead of this portal profiting from it: <a href="http://www.youtube.com/watch?v=keMpUaoA3Tg" rel="nofollow">http://www.youtube.com/watch?v=keMpUaoA3Tg</a>
Another cool physics experiment: What happens when you wring out a wet cloth in space?<p>Here's the answer:
<a href="http://youtube.com/watch?v=KFPvdNbftOY" rel="nofollow">http://youtube.com/watch?v=KFPvdNbftOY</a>
He had the large square magnet and the large round one within arms reach of each other so that he could swap them with one hand without walking away. That kind of freaks me out a little.
If you think that's cool you should have a look at this frog:<p><a href="http://www.youtube.com/watch?v=A1vyB-O5i6E&list=PL8E7ED16454FE1C63" rel="nofollow">http://www.youtube.com/watch?v=A1vyB-O5i6E&list=PL8E7ED16454...</a><p>The physics behind this are explained here: <a href="http://en.wikipedia.org/wiki/Magnetic_levitation" rel="nofollow">http://en.wikipedia.org/wiki/Magnetic_levitation</a>
Eddy currents are also used in exercise equipment with "magnetic resistance".<p><a href="http://www.bicycleman.com/recumbent-exercise-bikes/images/Magnetic-recumbent-bike-ECB.jpg" rel="nofollow">http://www.bicycleman.com/recumbent-exercise-bikes/images/Ma...</a>
For a similar effect using an MR scanner see the link below. I have done similar with an old door stop. <a href="http://www.youtube.com/watch?v=fxC-AEC0ROk" rel="nofollow">http://www.youtube.com/watch?v=fxC-AEC0ROk</a>
I wonder, with a tube that is of sufficient thickness and a magnet of sufficient strength, would it be possible to levitate the magnet inside the tube?
The slinky trick is better
<a href="http://www.youtube.com/watch?v=eCMmmEEyOO0" rel="nofollow">http://www.youtube.com/watch?v=eCMmmEEyOO0</a>