Why is the impedance LCR circuit capacitive at a frequency lower than resonant frequency?

1 Answer
Mar 13, 2018

The key is Inductive reactance and Capacitive reactance and how they are related to frequency of the applied voltage.

Explanation:

Consider an RLC series circuit driven by a volatge #V# of frequency #f#

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The Inductive reactance #X_l =2 * pi*f*L#

The Capacitive reactance #X_c =1/(2*pi*f*C)#

At resonace #X_l = X_C#

Below resonance #X_c >X_l#, so circuit impedance is capacitive

Above resonce #X_l >X_c#, so circuit impedance is inductive

If the circuit is parallel RLC, it gets more complicated.