Capacitive Impedance Demo
Capacitive Impedance Demo
Capacitive Impedance Demo

 

Code Number: 5C30.42

Demo Title: Capacitive Impedance Demo

Condition: Good

Principle: Parallel vs. Series Capacitance

Area of Study: Electricity & Magnetism

Equipment: 

150 V DC power supply, Capacitors (2), Light bulb (25 watt), Key switch, Digital or Overhead Volt Meter, Resistor, Knife Switch.

Procedure:

Hook the power supply, capacitor, light bulb, and Key switch in series as a circuit. Observe the voltages with and without the capacitor in the circuit. 

You can also add a second capacitor in parallel which doubles the time for charging.  As the voltage goes up on the meter the light will become dimmer.

CAUTION:  Do not go above 75 VDC on the power supply when adding the second capacitor.

The other part of the demo shown is the same as above except that a resistor replaces the light bulb. 

The two circuits may also be placed in parallel as shown.  

Another meter may be substituted for the overhead volt meter. 

References:

  • Baswajit Ray, "When Is a Capcitor NOT a Capacitor?", TPT, Vol. 44, # 2, Feb. 2006, p. 106.
  • Sudha Krishnan, Monoranjan Rao, "Hydrostatic Analogy for the Two-Capacitor Problem", AJP, Vol. 50, # 7, July 1982, p. 662.
  • En-4:  Freier and Anderson,  A Demonstration Handbook for Physics. 
  • Ronald Newburgh, "Two Theorems on Dissipative Energy Losses in Capacitor Systems", Physics Education, Vol. 40 # 4, July 2005, p. 370.
  • W. Bolton, "Capacitor in a d.c. Circuit", Book 4 - Electricity, Physics Experiments and Projects, 1968, p. 33.