Inductive Reactance


The Inductive Reactance of an inductor is how the impedance (or resistance) of the inductor changes in regard to the frequency of the signal passing through it.

Inductors, unlike resistors, are reactive devices. This means that they offer different resistances to signals of differing frequencies. To high-frequency signals, inductors offer a lot of resistance, so that high-frequency signals are essentially blocked from passing through an inductor. As the frequencies of the signals passing through an inductor decrease, the inductor offers less and less resistance, so that lower frequency signals can pass through easier.

Inductive Reactance Formula

The formula for calculating inductive reactance is:

Inductor Reactance Formula

XL is equal to the value of the inductor's reactance or impedance.

You can see, according to this formula, how inductive reactance changes according to the frequency of the signal input into it. It has an direct relationship with the frequency of the signal passing through it. The higher the frequency of the signal, the higher the value of the reactance. The lower the frequency of the signal, the lower the value of the reactance.


Using the inductive reactance (also called inductor impedance) formula above, we will now go through an example to show how the formula is used to compute actual inductor impedance values.

Let's say we have a circuit with an inductor of 30mH with an AC current of 10KHz frequency. What will the inductive reactance (or impedance) of the inductor be for this circuit?

And working it out and using the formula XL= 2πfL, we compute the value of the inductive reactance to be XL= 2π(10KHz)(30mH)≈ 1885Ω.

This value means that an inductor of 30mH with a 10KHz AC signal passing through it will have an impedance (resistance) of 1885Ω.

At our website, we have an online calculator to calculate inductive reactance. Check out this calculator at Inductor Impedance Calculator. This can calculate any inductive reactance, with the inductance and frequency values known.

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