Reactance & Resonance

Capacitive and inductive reactance at a frequency, the resonant frequency of an LC pair, and a series/parallel combiner for resistors and capacitors.

Capacitive reactance

Frequency

Capacitance

Xc = 1 ÷ (2πfC). Lower frequency or smaller capacitance means more reactance.

Inductive reactance

Frequency

Inductance

XL = 2πfL. Higher frequency or larger inductance means more reactance.

LC resonance

Inductance

Capacitance

f = 1 ÷ (2π√(LC)), the frequency at which an LC tank's reactances cancel.

Series & parallel combiner

Resistors (Ω, space-separated)

Capacitors (µF, space-separated)

Resistors add in series and combine by reciprocals in parallel. Capacitors are the opposite: they add in parallel and combine by reciprocals in series.