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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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 Electric Fields And Potential
  video  - Van de Graaff Generator
  video  - Electrostatic Bell
 Electric Lines of Force
 Electrostatic Motor
  video  - Electric Fields
  video  - Gauss' Law
 Radio in Faraday Cage
  video  - Fluorescent Bulb in Faraday Cage
  video  - Lightning Rod
  video  - Electric Wind
 Ionic Drive
  video  - Smoke Precipitator
 Current and Resistance
 Electromotive Force And Current
 DC Circuits
 Magnetic Materials
 Complex Circuits
 Semiconductors And Tubes
 Transmission Lines and Antennas

 video  - Gauss' Law


To show that excess charge resides totally on the outside of an insulated conductor.


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  DEMO VIDEO DOWNLOAD - HD - 1920x1080 / 27.4Mbps - 479MB size  

  DEMO VIDEO DOWNLOAD - LD - 854x480 / 5.69Mbps - 113MB size  

Charge the metal cylinder by touching it inside with a Teflon rod (charged with fur or silk) a few times. Show that there is a charge on the cylinder by bringing it close to the electroscope. Then lower the ball into the top opening of the cylinder making sure not to touch the edges. Extract the ball with the same care after banging it around inside the cylinder. Bring the ball near the electroscope and note the absence of charge. Now touch the outside of the cylinder with the ball and demonstrate with the electroscope that the ball is charged.


Be patient and careful. Ground the cage before the first trial, ground the ball on the rod between the sets, be mindful of not touching the edges of the cylinder while extracting the stick from inside.

On the Pasco ES-9054B Electrometer, it is best to use a scale setting of 30 or 100 Volts. Here is the instruction manual.

In case of wet weather, one can use the following trick: charge the cup with a Wimshurst machine (lots of charge that doesn't leak off very fast) and instead of electroscope use a pith ball. When attempting to take charge from the inside surface of the cup, the ball will stay immobile, while when attempting to take charge from outside surface of the cup, the ball will deviate.


  • Silk
  • Ball on the rod
  • Metal Cylinder on Stand
  • Electroscope
  • Teflon Tod
  • Cat's fur