5H40.30 Jumping Aluminum Ribbon


Lorentz force


When conducting, a ribbon of aluminum foil "jumps" up or down in a magnetic field.



  • [1] Aluminum foil ribbon
  • [4] Horseshoe magnet
  • [1] 6 V battery
  • [1] Telegraph switch
  • [3] Banana cable
  • [1] Insulated alligator clip
  • [1] Alligator clip
  • [2] Brass weight

Classroom Assembly

  1. Lay out aluminum foil ribbon with brass weights on the ends. Keep some slack in the foil.
  2. Connect the battery, switch, and foil in series using the cables and clips.
  3. Place the magnets in the desired configuration.

Important Notes

  • Red means a north pole and blue means a south pole.
  • If the demo does not work well, try adjusting the amount of slack in the foil.
  • When packing up this demo, make sure not to short the battery.
  • The aluminum foil becomes hot over time and the battery loses power quickly. Do not leave connected for longer than necessary.
  • The aluminum foil is delicate. Handle with care.


  1. Ask students to predict which way the foil will shift under each magnet.
  2. Close the switch. The foil should "jump" in the local magnetic field.


Additional Resources


  • PIRA 5H40.30


  • Don't attempt this at home!

Last revised

  • 2020


  • Original construction: the current carrying strip of aluminum foil is approximately 30" long x 0.5" wide and was cut from the edge of a roll. The horseshoe magnets were made in house by affixing a permanent magnet between two soft iron poles. The magnet/pole fixture is held in place by a brass top plate.

Related AV

Related demos

  • Lorentz force between parallel wires


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.