Physlet Illustration: Resonance in RLC Circuits

 

 
10 Ohms 100 Ohms 1000 Ohms
In this simulation, a 100 W resistor, 50 mH inductor, and a 20 microFarad capacitor are connected in series with a 10-Volt (maximum) AC source. The graph shows the current  in the circuit as functions of time. Vary the value of the source's angular frequency (5 rad/s < w < 5000 rad/s ) using the slider. What is the resonant frequency of the circuit? How does the resistance affect this resonance?

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. Is there an intermediate frequency where the current is high or low?  Why? 
  4. Measure the frequency where the peak current occurs.  Is this approximately what is expected given these components?
  5. Use the radio buttons to change the value of the resistor. Do changes in the resistance affect the resonant frequency?  What does the resistance affect?  

Reference

See Walker, Section 24-5

Illustration written by Chuck Niederriter