5K20.10-Eddy Current Pendulum

Video: Watch this demo | Demo #2

Instructor’s video

MIT video

Description: This demonstration shows the dampening force of a magnet on different discs.
A pendulum is made to swing between the poles of an electromagnet. When the electromagnet is turned on,
discs which allow for eddy currents will be damped, while those that do not allow eddy currents will not stop as fast.


  • Large DC Power supply
  • Eddy current pendulum
  • Multiple metal disks
  • 4 banana plug wires

Setup Procedure:

  1. Attach the solid disk to the pendulum.
  2. Connect the apparatus to the power supply. Use two cables in parallel per terminal due to high currents.
  3. Test to make sure the pendulum stops when power is applied.

Demonstration Procedure:

  1. Insert the appropriate disk into the pendulum
  2. Turn on the power supply with the switch open.
  3. Set the power supply to 10VDC.
  4. Pull the pendulum back and let go.
  5. When you want to damp the oscillation, close the switch to apply power.

Caution: This apparatus is VERY heavy. Two people may be needed to lift this.