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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Electrostatics
Electric Fields And Potential
Capacitance
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
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video - RC Circuit w/ Function Generator

Purpose:

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.

Procedure:

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).

Hints:

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.

Equipment:

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