Jumping Discs, 4A30.40

Location:

• Cabinet: Thermodynamics Cabinet

• Bay: (A3)

• Shelf: #3

(attachment photo showing the fully set up demonstration)

Description:

Also called hopping discs, bimetallic jumpers. This demo is consisted of various jumping discs.

Setup:

1. Hold the Jumping Disc in your palm.
2. Rub the silver side with your thumb until you feel warm. Then press down on the silver side until it clicks and make sure that it stays in the clicked-in position.
3. Put the Jumping Disc on a cool, hard smooth surface such as the lecture table with the silver face down.
4. Stand back! Jumping Disc will jump into the air.

Cautions, Warnings, or Safety Concerns:

1. Do not put the Jumping Disk on a fine wooden furniture as it may scratch the surface. It is so powerful in its reaction.
2. If the Jumping Disk is not still in the clicked-in position, keep rubbing it until you put it down.

Demonstration:

The Jumping Disk is a bimetallic disc that consists of stainless steel on one side and invar(nickel-iron alloy)on the other. The coefficient of linear expansion of the invar is much lower than that of the stainless steel. When you rub the silver side (stainless steel), heat cause the bimetallic disc to expand. then the cooling makes it contract. The change from the warm and cool caused the bimetallic disc to change shape immediately and jump into the air, because the two surfaces expand and contract at highly different rates due to the change in temperature.

References:

1. EDMUND SCIENTIFIC CO.

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