Which phenomenon occurs when the inductive and capacitive reactance cancel in a circuit?

Which phenomenon occurs when the inductive and capacitive reactance cancel in a circuit?

• A. Resonance
• B. Impedance
• C. Reactance
• D. Attenuation

Answer: (A)

The concept being tested is resonance—the condition where the inductive reactance and the capacitive reactance balance and cancel each other. When XL equals XC, their reactive effects oppose one another and sum to zero, leaving the impedance purely resistive (Z ≈ R) at that frequency. In a simple LC circuit, this occurs at the resonant frequency f0 = 1/(2π√(LC)). At resonance, the current in a series circuit is maximized for that frequency because the reactive opposition vanishes, and energy continuously sloshes between the magnetic field of the inductor and the electric field of the capacitor. This is distinct from impedance in general, which is the total opposition to current; the cancellation of reactive parts at resonance is the defining feature of the phenomenon.

The concept being tested is resonance—the condition where the inductive reactance and the capacitive reactance balance and cancel each other. When XL equals XC, their reactive effects oppose one another and sum to zero, leaving the impedance purely resistive (Z ≈ R) at that frequency. In a simple LC circuit, this occurs at the resonant frequency f0 = 1/(2π√(LC)). At resonance, the current in a series circuit is maximized for that frequency because the reactive opposition vanishes, and energy continuously sloshes between the magnetic field of the inductor and the electric field of the capacitor. This is distinct from impedance in general, which is the total opposition to current; the cancellation of reactive parts at resonance is the defining feature of the phenomenon.