5H40.71-Rolling rod

Video: Watch this demo

Description: This demonstration visually shows the interaction between a magnetic field and a current carrying rod.


  • Large DC power supply
  • Large magnet
  • Two rods with connectors attached.
  • Lightweight/Thin metal rod
  • DPDT switch
  • 2 table clamps
  • 2 long poles
  • 2 S clamps
  • 6 banana plug cables
  • Medium Fine grit sand paper or abrasive pad

Setup Procedure:

  1. Attach the two rods to a table using the above equipment. Make sure they are level.
  2. Connect the two rods to a DPDT switch. Connect the switch to the power supply.
  3. Rub the abrasive pad on the two stationary rods and the small rod (improves contact).
  4. Position the large magnet under the two rods.
  5. Set the power supply to high and test to make sure it works.

Demonstration Procedure:

  1. Place the small rod on the two large rods.
  2. Turn on the power supply and close the switch to move the rod. The rod moves because the current in the rod produces a magnetic field that opposes that of the permanent magnet, thus creating a force between the two.
  3. Move the switch to the other position to make the current flow in the opposite direction. The rod will move in the opposite direction.
  4. When finished, turn off the power supply.

High Current
This power supply outputs 20-30A at low voltage. Although the voltage is low, caution should still be used.