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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


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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 Thermal Properties Of Matter
 Heat And The First Law
 Change Of State
 Kinetic Theory
  video  - Brownian Motion
 Crookes Radiometer (Light Mill)
  video  - Kinetic Theory
 Gas Law
 Entropy And The Second Law

 video  - Kinetic Theory


To show a model of kinetic theory using a 2-dimensional box holding steel ball bearings.


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Small metal balls are contained in a holder between glass plates. Container is mounted on a PASCO Mechanical Vibrator. The piston connected to the vibrator is inserted through the bottom of the container. Plastic slide acting like a freely moving piston is inserted through the top of the container. The image is projected onto a screen by an optical apparatus and projector.

Vibrator is driven by a function generator and causes the balls to move and simulate the motion of the molecules of a gas. When the amplitude of the motion of the piston is increased the balls move with greater speed and greater mean-free-path. This causes the lid on the top of the container to rise and simulate an increase in temperature.

A small plastic disk can be inserted in the container to demonstrate Brownian motion. Different sizes disks are available to show Brownian motion dependence of the particle size.

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  • Function generator should be set to approx 30 Hz. If the balls are not vibrating, check the lock lever on the mechanical vibrator.
  • Place glass ball bearing plates holder at an angle to projector/lens to prevent light reflection from showing up on screen