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Teaching in LA

03 Dec

Magnet Through a Copper Tube

Posted in Uncategorized on 03.12.11 by Frank

Drop a magnet down this non-magnetic copper tube and witness the magic (physics) that is Lenz’s Law (or Eddy Currents… or… something).


  • A ~ 5 ft. copper pipe (I used 1/2″ diameter, might have to ask to get it cut to length at hardware store)
  • Strong “disc” or “ring” neodymium magnets with diameter less than pipe, (available for reasonable prices by searching for “neodymium magnets” on eBay)


  1. Establish that the copper is not magnetic. Have a student use the magnets to pick up something magnetic (paper clips, nose ring, etc.), then attempt to attract the copper pipe. It shouldn’t work. :o|
  2. Establish that gravity functions properly through the copper pipe. Have the student hold the pipe vertically, then drop an object (pen) through the pipe. Did the pen seem to accelerate down through the pipe at approximately 9.8 m/s/s? If yes, then physics is working.
  3. Do the same demonstration, but with a short stack of magnets long enough that they don’t flip in the pipe. After you drop the magnets at the top of the pipe, take a leisurely stroll to your desk and back, then reach out to catch the magnet.

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