Rinnakkaisresonanssipiiriä

Rinnakkaisresonanssipiiri, also known as a parallel resonant circuit, is an electrical circuit consisting of an inductor and a capacitor connected in parallel. When the frequency of the AC voltage source applied to the circuit matches the resonant frequency, the impedance of the circuit becomes very high. This phenomenon is called parallel resonance.

The resonant frequency (f_r) of a parallel resonant circuit is determined by the values of the inductance (L) and capacitance (C) according to the formula f_r = 1 / (2 * pi * sqrt(L*C)). At resonance, the inductive reactance (X_L) and capacitive reactance (X_C) are equal in magnitude but opposite in phase. This causes the reactive currents circulating within the inductor and capacitor to cancel each other out.

The effective impedance of the parallel resonant circuit at resonance is theoretically infinite in an ideal circuit with no resistance. In a real circuit, however, the impedance is finite and depends on the resistance present, often the inherent resistance of the inductor's coil. The high impedance at resonance means that very little current flows from the source to the circuit, while a large current can circulate between the inductor and capacitor.

Parallel resonant circuits are commonly used in radio frequency applications, such as tuning circuits in receivers and transmitters, band-stop filters, and oscillators. Their ability to exhibit high impedance at a specific frequency makes them useful for selecting or rejecting particular frequencies.