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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
 Current and Resistance
 Electromotive Force And Current
 DC Circuits
 Ohm's Law
 Resistivity of a Pencil
 Resistive Heating of Nichrome Wire
 Blowing a Fuse
 Wheatstone Bridge
  video  - Wheatstone Bridge II
  video  - Circuit Analysis
  video  - RC Circuit w/ Function Generator
 RC Circuit w/ Battery
 RC Time Constant (DECAY)
 Telephone model as simple DC circuit
 Magnetic Materials
 Complex Circuits
 Semiconductors And Tubes
 Transmission Lines and Antennas

Resistivity of a Pencil


To show that the resistance of a piece of material (in this case graphite) is proportional to its length.


Connect the bulb, battery and pencil in series. The bulb can be dimmed or brightened by sliding one of the connectors along the exposed graphite of the pencil.


  • Light Bulb
  • D battery
  • leads
  • Pencil