Ac Electricity
Reactance
Reactance is the frequency-dependent opposition that inductors and capacitors present to alternating current. Inductive reactance is X_L = 2πfL and rises with frequency and inductance. Capacitive reactance is X_C = 1/(2πfC) and falls as frequency and capacitance rise. Both are measured in ohms, but unlike resistance they do not dissipate active power; they exchange energy with the source.
Reactance
X_L = 2π × f × L; X_C = 1 ÷ (2π × f × C)
Variables and units
| Symbol | Quantity | Unit |
|---|---|---|
| X_L | Inductive reactance | Ω |
| X_C | Capacitive reactance | Ω |
| f | Frequency | Hz |
| L | Inductance | H |
| C | Capacitance | F |
Conditions of application
Sinusoidal steady state. Inductive reactance rises with frequency; capacitive reactance falls with frequency. Reactance is measured in ohms but does not dissipate active power.
Worked example
Solved
Put this formula to work
Electrical Unit Converter →
Convert voltage, current, resistance and power between SI prefixes.