4A30.40 - Spencer Disks

Code Number:
Demo Title:
Spencer Disks
Expansion & Contraction with Temperature Variation
Area of Study:
Heat & Fluids
Spencer Disks - Jumping Disks (Bimetal Disks) and Aluminum Block.

Warm the jumping disks with your hand and press it to the click position.  Set the disk on a cool level surface.  In a few seconds the transfer of heat from the disk to the level surface will cause the bimetal disk to snap back to its original position causing the disk to jump into the air as it does so.

This demo may be enhanced by using an aluminum block heat sink that has been placed in the freezer for several hours.

  • Ed McNell and Earl Zwicker, "Newton's Laws with Jumping Disks", TPT, Vol. 26, #5, May 1988, p. 308.
  • "H-122. Jumping Disks", DICK and RAE Physics Demo Notebook, 1993.
  • G. D. Freier and F. J. Anderson, "Ha-11", A Demonstration Handbook for Physics.
  • Robert Ehrlich, "I.3. Bimetallic Jumping Disks", Turning the World Inside Out and 174 Other Simple Physics Demonstrations, p. 114 - 116.

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