5K20.23 Eddy Current Ramps


Faraday's law, Lenz' law, magnetic fields from currents


A magnet sliding down a copper ramp is slowed by magnetic fields from eddy currents induced in the tube. A magnet sliding down a Plexiglas ramp is unaffected. A magnet sliding down a brass ramp goes faster than on the copper ramp due to the higher resistivity of the brass damping the currents.



  • [1] Ramp holder
  • [1] Copper, Plexiglas, and brass ramps
  • [3] Rare earth magnets 

Classroom Assembly

  1. Mount the appropriate ramps at the desired slant at the labelled locations.

Important Notes

  • Make sure the magnets don't slam into each other. They can break when that happens.


  1. Slide a magnet down the Plexiglas ramp. Remove the magnet.
  2. Ask for predictions on what will happen with the copper ramp.
  3. Slide a magnet down the copper ramp. Remove the magnet.
  4. Ask for predictions on whether the magnet will slide down faster on the brass or copper ramp.
  5. Slide magnets down the copper and brass ramps simultaneously.


Additional Resources


  • PIRA 5K20.23


  • Don't attempt this at home!

Last revised

  • 2020


Related AV

Related demos

  • Eddy current tubes


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.