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

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 $f$

The Inductive reactance ${X}_{l} = 2 \cdot \pi \cdot f \cdot L$

The Capacitive reactance ${X}_{c} = \frac{1}{2 \cdot \pi \cdot f \cdot C}$

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.