Inductive and Capacitive Reactances

Inductive Reactance:

It is the opposition to the current flow in an AC circuit that contain only inductance element and we refer to it by the symbol (XL). If the circuit contains resistance and reactance, the total opposition to the current flow called impedance and we refer to it by the symbol (Z).

When an AC current passes throw an inductance, counter EMF is generated and trying to oppose changes in the current. This opposition is called inductive reactance (XL).

Inductive reactance is measured in ohm and proportional to the value of inductance and the value of the applied frequency according to the following formula:

XL = 2 π F L where π = 3.14, L =value of inductor in henry.

Z = √ (R²+XL² )

Phase relationship between applied voltage and current:

In pure resistive load, current and voltage are in phase (angle = 0) and in pure inductive load, the current lag the voltage by an angle equal to 90 degree and it said to be out of phase. In a circuit contain inductive reactance and resistance the current will lag the voltage by an angle in between (0) degree and (90) degree depending on the ratio between the amount of inductive reactance components to resistive components, as the more resistive component the more in phase relationship and vice versa.

Capacitive Reactance:

It is the opposition to the current flow in an AC circuit that contain only capacitive element and we refer to it by the symbol (XC). If the circuit contains resistance and capacitance, the total opposition to the current flow called impedance and we refer to it by the symbol (Z).

Capacitive reactance is measured in ohm and it increases when the value of capacitor capacitance decreased according to the following formula:

XC =1 / (2π F C)          where π = 3.14,   C = value of capacitance in farad.

Z = √ (R²+XC² )

Phase relationship between applied voltage and current:

In pure capacitive load, current lead voltage by an angle equal to 90 degree and it said to be out of phase. In a circuit contain capacitive reactance and resistance, the current will lead the voltage by an angle in between (0) degree and (90) degree depending on the ratio between the amount of capacitive reactance components to resistive components as the more resistive component the more in phase relationship and vice versa.