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Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography

PLEASE REQUEST DEMOS WELL IN ADVANCE

Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

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 Surface Tension
 Surface Tension
 Surface Tension with Electric Field
 Soap Films
 Capillary Tubes
 Fluid Statics
 Fluid Dynamics

Surface Tension

Purpose:

To show some of the effects of surface tension in water.

Procedure:

Provide plenty of beakers and fresh water if instructor expects to do multiple demos. Use wide Pyrex dish for razor blade "jumping" demo, and deep beaker for weight-cork-loop apparatus.
  1. Float the cotton in the jar and add a drop or two of wetting solution. The cotton will begin to sink.
  2. Float the razor blade in the water and place a small drop of wetting solution in the center. The reduction of surface tension will cause the blade to be propelled around the surface of the water.
  3. The plates can be firmly stuck together using a few drops of water placed between them.
  4. The weight-cork-loop apparatus is shown to float in water with the weight down. If one pushes the apparatus down until it it is submerged, it will remain under water due to the wire loop being pushed down vy the water surface tension. Submerged float stays submerged until soap is added to reduce the surface tension.
  5. Silicon vapor treated sand becomes non-polar and wets in oil but not water. The oil spills can be collected by pouring the Space Sand over an oil spot on the water.

Hints:

Razor blade must have one end cut off.

Equipment:

  • Glass Adhesion Plates
  • Large Flat-Bottomed Bowl
  • Non-Absorbent Cotton
  • Razor Blade