Probably the most important concept in electrical engineering and physics involves inductive reactance and how it especially relates to the study of AC circuits. Inductive reactance is the opposition that the inductor presents to alternating current due to its ability to store energy within a magnetic field.

Inductive reactance(XL)​, is a measure of the extent to which an inductor opposes any change in current in an alternating current circuit. Unlike resistance, inductive reactance does not dissipate energy into heat; instead, inductive reactance stores energy in a magnetic field produced by an inductor. The higher the inductance or frequency of the AC signal, the higher is the inductive reactance.

The Formula for Inductive Reactance

The following formula determines inductive reactance:

Where:

• XL is the inductive reactance, expressed in ohms, Ω,

• f  is the frequency of the AC signal, expressed in hertz, Hz,

• L is the inductance of the coil, expressed in Henries, H.

Solved Problems 

Problem 1: An inductor of 2H is connected to a circuit at a frequency of 50Hz. Compute the inductive reactance of this circuit?

Solution: 

Given,

f=50Hz

L=2H

The inductive reactance formula is given as,

XL  = 2×3.14×50×2

XL   = 628 Ω

Problem 2: At what frequency does a 250 mH inductor have 3.5 kΩ of reactance?

Solution: 

Given, 

XL=3.5 

kΩ =3500Ω

f=? and

L = 250mH = 0.25H

The inductive reactance can be computed by the following expression,

 

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