Lecture Demonstrations Laboratory

The Demonstrations Manual

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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; Wheatstone Bridge II; Circuit Analysis; RC Circuit; RC Time Constant (DECAY); Telephone model as simple DC circuit
Magnetic Materials
Magnetism
Inductance
Induction
Complex Circuits
Semiconductors And Tubes
Transmission Lines and Antennas

RC Circuit

Purpose:

To demonstrate the time constant of an RC circuit and its dependence on R and C.

Procedure:

Connect R and C in series and use the PASCO generator's square waves as a signal source. Start with 100Ohm resistor and 0.47uF 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:

To reduce the time constant two resistors could be quickly put in parallel by stacking them on top of each other.
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 room 203.

Comments:

If you have a suggestion for the use of this demo which might benefit others, you can enter it below.

Equipment:

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