a quantity characterizing the opposition presented to an alternating current by the inductance of a circuit or of part of a circuit. Inductive reactance is measured in ohms.
In the case of a sinusoidal current, the inductive reactance xL can be expressed as the product ωL, where ω is the angular frequency of the current and L is the inductance of the circuit. Inductive reactance is equal to the ratio of the amplitude of the voltage applied to the terminals of the circuit and the amplitude of the current through the circuit if the circuit has an inductive character (that is, has little resistance and fairly large inductance); such a circuit can be regarded as equivalent to an inductance coil. When direct current is in the coil (ω = 0), the inductive reactance is equal to zero. When alternating current flows through the coil, electrical energy is transferred from the current source to the magnetic field of the coil and then back to the current source; the average power during a period is equal to zero.