Resonance

Resonance occurs in an electric circuit at a particular resonance frequency when the impedance between the input and output of the circuit is at a minimum.

f=\frac{1}{2\pi \sqrt{LC}}

L=\frac{1}{\left( 2\pi f \right)^2C}

C=\frac{1}{\left( 2\pi f \right)^2L}

More info: http://en.wikipedia.org/wiki/Electrical_resonance