I want to answer as many of my science questions as I can during the spring break so I can put the information to use.
They make either a series or parallel tuned circuit. Series circuits are high impedance at the resonant frequency and parallel cirsuits are low impedance at resonance.
Formulas can be found in any basic Ac electrical text. Ham Radio study guides have it as well. see my other answer
A capacitor has reactances at different frequencies. An inductor has reactances at different frequencies. A capacitor/inductor combination will have a frequency at which the reactances, or impedances cancel each other out. This is called the resonant frequency.
The inductor-capacitor (LC) combination picks (selects) a particular wave frequency in two different ways. If connected in series their capacitance and inductance values can be selected such that their individual impedance is equal to each other`s and their combined impedance to the selected frequency is zero ohms. This will allow the selected (picked) frequency to pass through the LC combination with no impedance while at the same time it will present a high impedance to all the undesired frequencies above or below the selected frequency. Hence the output of the series connected LC combination would be the place where the picked (selected) frequency would be predominantly available. If connected in parallel their capacitance and inductance values can be selected such that their individual impedance values are equal to each other. At these values their combined impedance will be approaching infinity to the selected (picked) frequency. This parallel combination will offer maximum impedance to the selected frequency and a lesser impedance to the frequencies above and below the selected frequency. Hence the input of the parallel connected LC combination would be the place where the selected (picked) frequency would be predominately available.
