Editing Inductor (section)

===Reactance===
The ratio of the peak voltage to the peak current in an inductor energised from an AC source is called the [[electrical reactance|reactance]] and is denoted ''X''<sub>L</sub>.

:<math>X_\mathrm L = \frac {V_\mathrm P}{I_\mathrm P} = \frac {\omega L I_\mathrm P}{I_\mathrm P} </math>

Thus,

:<math>X_\mathrm L = \omega L </math>

where ''ω'' is the [[angular frequency]].

Reactance is measured in ohms but referred to as ''impedance'' rather than resistance; energy is stored in the magnetic field as current rises and discharged as current falls.  Inductive reactance is proportional to frequency.  At low frequency the reactance falls; at DC, the inductor behaves as a short circuit.  As frequency increases the reactance increases and at a sufficiently high frequency the reactance approaches that of an open circuit.