The kind of Resonance

Three kinds of resonant frequency in circuits are officially defined.

 

Phase resonance is the frequency at which the phase angle between sinusoidal current entering a circuit and sinusoidal voltage applied to the terminals of the circuit is zero.

Amplitude resonance is the frequency at which a given sinusoidal excitation (voltage or current) produces the maximum oscillation of electric charge in the resonant circuit.

Natural resonance is the natural frequency of oscillation of the resonant circuit in the absence of any forcing excitation.

 

These three frequencies are so nearly equal in low-loss circuits that they do not often have to be distinguished.