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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

 video  - RC Circuit w/ Function Generator


A square wave charges and discharges a capacitor and the charging time is observed on the oscilloscope. To demonstrate the time constant of an RC circuit and its dependence on R and C.


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  DEMO VIDEO DOWNLOAD / no audio / 1920x1080 / 24.19Mb/s / 567MB size  

  DEMO VIDEO DOWNLOAD / no audio / 854x480 / 5.69Mb/s / 135MB size  

Connect R and C in series and use the PASCO generator's square waves as a signal source. Start with 100 Ω resistor and 0.47 μF capacitor and display the voltage across the capacitor (see 2nd picture). Vary the values of C and R (provided) to show the change of the time constant. Show the voltage across the resistor to demonstrate the current dependence in the circuit (see 3rd picture). A schematic of the set up is shown below (4th picture).


New Tektronix DPO 3014 Scope Setup:
  • There are two Instek GDP-025 differential probes attached to CH1 and CH2.
  • Scope has VGA output whose signal can be projected onto screen.
Old HP 1200A Scope Setup:
  • Use differential input oscilloscope to display both the charge and the current dependence.
  • A camera pointing at the scope's screen is available for the use in any of the rooms.
To reduce the time constant two resistors could be quickly put in parallel by stacking them on top of each other.


  • Oscilloscope
  • Connecting Wires
  • Large Bread Board
  • Resistor - Capacitor Substitution Box
  • Wave Generator