9.8 : 直列共振

Consider a radio tuner that precisely selects a signal of a particular frequency.

The tuner consists of a series-connected resistor, capacitor, and inductor.

The RLC frequency domain circuit impedance is the ratio of the supply voltage to the circuit current.

Resonance occurs when the imaginary part of this impedance equals zero.

This means that the inductive reactance equals the capacitive reactance.

The frequency where this condition is met is called the resonance frequency and is inversely proportional to the square root of the inductance and capacitance product.

At this resonant frequency, the inductor and capacitor series combination are like a short circuit, making the circuit purely resistive.

This results in the voltage and current being in phase, creating a unity power factor.

The impedance reaches its minimum magnitude, allowing maximum current flow through the circuit.

The voltage across the inductor and capacitor exceeds the source voltage significantly.

Resonance enhances the signal strength for the selected channel and improves the overall broadcast quality.