What Is Inductive Reactance

Inductive reactance is the resistance offered by the inductor in an AC circuit to the flow of ac current. XL is the symbol for it, and it’s measured in ohms. Lower frequencies have a low inductive reactance, while higher frequencies have a greater one. For constant DC current, however, it is negligible.

What Is Inductive Reactance

The inductive reactance of a coil relies on the frequency of the applied voltage as reactance is precisely proportional to frequency. When a DC voltage is put across an inductor, the self-induced or back emf value of the inductor determines the increase of the current through it. 

Actually, the current flow through an inductor behaves substantially differently when an alternating or AC voltage is applied to it. The phase difference between the voltage and current waveforms is caused by a sinusoidal supply.

When an inductor is employed in an AC circuit, its electrical resistance is referred to as inductive reactance. Inductive Reactance, abbreviated as XL, is a property in an AC circuit that opposes the change in current. In a fully inductive AC circuit, the current IL lags the applied voltage by 90-degree, or (π/2 rads).

AC Inductor Circuit

The self-induced back emf in the inductor coil grows and reduces with the frequency as the supply voltage rises and drops. We know that this self-induced emf is related to the rate of change of current through the coil.                                                                                                                               

AC Inductance and Inductive Reactance in an AC Circuit (electronics-tutorials.ws)

It is largest when the supply voltage switches from positive to negative half cycle, or vice versa, at points 0 degrees and 180-degree along with the sine wave. As a result, the AC sine wave passes over at its threshold peak voltage level, resulting in the lowest voltage change rate. Maximum and minimum currents flow through the inductor circuit at these points in the cycle.

Inductive Reactance

The preceding equation for inductive reactance can be rewritten in a more known form that uses the supply’s ordinary frequency instead of the angular frequency in radians, as follows:

Where F is the frequency, L is the coil’s inductance, and 2πƒ = ω. 

Inductive Reactance Against Frequency

It can be seen from the preceding equation for inductive reactance that increasing either the frequency or the inductance will raise the overall inductive reactance value. As the frequency approaches infinity, the reactance of the inductors increases to infinity, serving as an open circuit.

The inductor’s reactance would reduce to zero as the frequency approached zero or DC, resulting in a short circuit. As mentioned before, inductive reactance is “proportional” to frequency, according to this definition. 

Inductive reactance, in other words, increases with frequency, resulting in XL being small at low frequencies and high at high frequencies.

Conclusion

Understanding inductive reactance is necessary to figure out the overall response of the circuit. AC circuit is of concern here as the reactance is highly related to frequency. Hopefully, the above information will help to get a clear perception of what inductive reactance is.