When finding resonant frequency, you find the equivalent admittance or impedance and set the imaginary part equal to 0 or infinity. I choose to use admittance because the resulting calculations are usually easier. The problem I'm having, however, is in knowing when the admittance is infinite and when it is zero. In traditional parallel circuits admittance is infinite and in series circuits it is zero. What I don't understand is, what is it when the circuit is a mixture of both?. Can anyone clarify? The following examples are some problems where it isn't clear. In the first and second circuits, the admittance is equal to zero. In the third, it's equal to infinity. I can't figure out why, however.
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