Reactance is the opposition inserts by a pure coil or a capacitor to the flow of alternating current through it. A pure coil or capacitor is one without any resistance in it. The opposition offered by a resistor to the flow of current is termed as resistance. Resistance Dissipates energy in the form of heat. Reactance diminishes current by setting up an opposing EMF and therefore controls a source of alternating emf without wastage of electrical energy.
There are two type of reactance
1. Inductive reactance
2. Capacitive reactance
Reactance of a coil, called inductive reactance, it is denoted by XL. Inductive reactance is depends the frequency of an AC and inductance of the coil. If frequency (f) in fz and Inductance (L) in henries then inductive reactance XL is given by XL = 2πfL
Reactance of a capacitor, is called capacitive reactance, it is denoted by XC. Inductive reactance is depends the frequency of an AC and capacitance of capacitor. If frequency (f) in and capacitance (c) then capacitive reactance XC is given by XC = 1 / 2πfc
Note1. Both capacitive reactance and Inductive Reactance is measured in Ohms
Note2. The combination of Reactance and resistance is called impedance.