At resonance, what is the impedance of parallel tuned circuits?

At resonance, a parallel tuned circuit presents a very high impedance to the source of the signal. This characteristic occurs because, at the resonant frequency, the reactive components of the circuit—the inductor and capacitor—tend to cancel each other out. This results in minimal current being drawn from the source at that frequency.

In a parallel circuit, the inductor reacts with energy storage in its magnetic field, while the capacitor reacts with energy storage in its electric field. At resonance, the inductive reactance becomes equal to the capacitive reactance, leading to a situation where the circuit effectively behaves as if it has an infinitely high resistance at that particular frequency, preventing significant current flow through the circuit.

This behavior is crucial for applications in amateur radio, such as tuners and filters, where maximizing the impedance at the desired frequency helps to ensure that maximum power transfer occurs only at the resonant frequency, thereby improving the efficiency and effectiveness of signal transmission and reception. The other choices do not accurately describe the behavior of a parallel tuned circuit at resonance; hence, they do not correctly represent the impedance characteristics observed in practice.