Physlet Illustration: Capacitive Reactance

 

 
In this simulation, a 100 W resistor and a 1 mF capacitor are connected in series to a 10-Volt (maximum) AC source. The graph shows both the voltage and current  in the capacitor as functions of time. Vary the value of the source's angular frequency (500 rad/s < w < 5000 rad/s ) using the slider. How do this affect the current in the capacitor?

Hints:

  1. As you increase w to a very high frequency, does the current increase or decrease? Why?
  2. As you decrease w to a very low frequency, does the current increase or decrease? Why?
  3. Set a particular frequency. What is the capacitive reactance at this frequency? The impedance of the circuit? What, then, should be the maximum current?
  4. What is the phase relationship between the voltage and current in the capacitor? Does this relationship depend upon the frequency?

Reference

See Walker, Sections 24-2 and 24-3

Illustration written by Steve Mellema