Reatância Indutiva
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
X_L = 2πfL
About this calculator
The inductive reactance calculator determines the opposition that an inductor offers to alternating current, given by the formula X_L = 2πfL. In this equation, X_L is the inductive reactance in ohms, f is the frequency in hertz, and L is the inductance in henrys. The term 2πf represents the angular frequency, which relates to the time variation of AC. This quantity is fundamental in AC circuits, as it directly affects the total impedance and the behavior of filters, transformers, and electric motors.
The calculator works simply: the user inputs frequency and inductance values, and the tool applies the formula to compute the inductive reactance. It is important to note that inductive reactance increases with frequency, meaning higher frequencies result in greater opposition from the inductor. This explains why inductors are used to block high-frequency signals in electronic circuits, such as in low-pass filters. The calculator can also be useful for sizing components in power electronics, switched-mode power supplies, and power transmission systems.
When to use this calculator? It is ideal for students and professionals in electrical and electronic engineering who need to analyze AC circuits. For example, when designing a filter for an audio amplifier, calculating inductive reactance helps determine the cutoff frequency. It is also useful in labs for experimentally verifying inductor behavior. However, caution is needed: the formula assumes ideal inductors with no internal resistance or parasitic capacitance. At high frequencies, parasitic effects may reduce accuracy.
Additional care: the calculator expects positive values for frequency and inductance. Ensure consistent units (hertz and henrys). For inductors with ferromagnetic cores, inductance may vary with current, which is not considered in this simple calculation. Also, in resonant circuits, inductive reactance combines with capacitive reactance to form total impedance. Thus, this tool is a starting point, but more complex analyses may require simulations or practical measurements.
Frequently asked questions
What is the difference between inductive reactance and impedance?
Inductive reactance is the opposition caused only by inductance, while impedance includes resistance and capacitive reactance as well. In circuits with resistance and inductance, total impedance is the vector sum of resistance and inductive reactance.
Can inductive reactance be negative?
No, inductive reactance is always positive because inductance and frequency are positive quantities. Capacitive reactance, on the other hand, is negative in the formula, but both contribute to total impedance.
How does frequency affect inductive reactance?
Inductive reactance is directly proportional to frequency: if frequency doubles, reactance also doubles. This means inductors offer greater opposition to high-frequency currents.
Can I use this calculator for iron-core inductors?
Yes, but with caution. The inductance of ferromagnetic core inductors can vary with current and frequency due to saturation and losses. The calculation assumes constant inductance, so results are approximate.
What is the unit of measurement for inductive reactance?
Inductive reactance is measured in ohms (Ω), the same unit as resistance. This is because both represent opposition to electric current.