5K20.25 Eddy Current Tubes
Faraday's law, Lenz' law, magnetic fields from currents
A magnet falling down a copper tube is slowed by magnetic fields from eddy currents induced in the tube. A magnet falling down a glass tube is unaffected.
-  Lab stand
-  Glass tube
-  Copper tube
-  3-finger clamp
-  90-degree clamp
-  Bell
-  Aluminum slug
-  Magnet
-  Plastic container
- Set up lab stands, each with a 3-finger clamp holding a tube and a bell mounted just below the tube.
- Put the plastic container under the bells to catch the magnet and slug when they fall.
- Using either the document camera or overhead projector, show the class that the aluminum slug and magnet are the same diameter.
- Put the aluminum slug through both tubes, showing there are no obstructions inside. The bells will ring when the slug hits them.
- Put the magnet through the glass tube, showing how it falls as the aluminum slug did.
- Put the magnet through the copper tube. In about 8 seconds, it will make a very light "ding" sound on the bell.
- PIRA 5K20.25
- Don't attempt this at home!
- Use a non-ferromagnetic 3-finger clamp to hold the copper tube. Otherwise, there is a small (~10%) chance of the magnet stopping next to the clamp.
- Jumping rings
- Superconducting train
- AC induction
- Solenoid induction with a battery
- Permanent magnet induction
- Eddy current ramps
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.