Reactance is essentially inertia against the motion of electrons. It is present anywhere electric
or magnetic fields are developed in proportion to applied voltage or current, respectively; but most
notably in capacitors and inductors. When alternating current goes through a pure reactance, a
voltage drop is produced that is 90o out of phase with the current. Reactance is mathematically
symbolized by the letter “X” and is measured in the unit of ohms (Ω).