37.6991
Ω
376.9911
rad/s
0.1
H
3.183099
A
37.6991
Ω
376.9911
rad/s
0.1
H
3.183099
A
The Inductive Reactance Calculator computes the opposition to alternating current offered by an inductor at a given frequency. Inductive reactance (Xₗ) is a key parameter in AC circuit analysis, determining how much an inductor impedes the flow of alternating current based on both its inductance value and the signal frequency.
An inductor stores energy in a magnetic field when current flows through it. When the current changes—as it continuously does in an AC circuit—the inductor generates a back-EMF (electromotive force) that opposes the change. The faster the current changes (higher frequency), the greater this opposing voltage, and consequently the greater the reactance. This is captured by the formula Xₗ = 2πfL.
Inductive reactance is measured in ohms (Ω) and behaves like a frequency-dependent resistance, but with a crucial difference: it does not dissipate energy. Instead, energy is alternately stored in the magnetic field and returned to the circuit. This storage-and-return cycle causes the current to lag behind the voltage by 90° in a purely inductive circuit.
This property makes inductors invaluable in many applications. In power systems, the reactance of generators, transformers, and transmission lines governs power flow and voltage regulation. In radio frequency circuits, inductors are used in tuning circuits, matching networks, and oscillators. In power electronics, inductors smooth out current ripple in switch-mode power supplies. In audio systems, inductors in crossover networks direct low-frequency signals to woofers.
The calculator accepts frequency in hertz and inductance in millihenrys, then computes the inductive reactance along with the angular frequency and a reference current value. For engineers and students, this tool provides a quick way to evaluate how an inductor will perform at any operating frequency, helping to select appropriate component values for circuit design.
Understanding inductive reactance is essential for grasping impedance, resonance, filter design, and power factor correction—all cornerstone concepts in electrical engineering and electronics.
The inductive reactance calculator uses the fundamental formula:
$$X_L = 2\pi f L = \omega L$$
where:
The calculator converts the input inductance from millihenrys (mH) to henrys (H) by dividing by 1000:
$$L_{H} = \frac{L_{mH}}{1000}$$
A reference current at 120V is also computed using Ohm's law for AC:
$$I = \frac{V}{X_L} = \frac{120}{X_L}$$
This shows how much current an ideal inductor would draw from a 120V AC source at the given frequency.
The inductive reactance value tells you the effective opposition (in ohms) that the inductor presents at the specified frequency. A higher reactance means less current will flow. At low frequencies, the reactance is small and the inductor behaves almost like a short circuit. At high frequencies, the reactance is large and the inductor blocks most of the current. The reference current at 120V helps visualize the practical effect of the reactance value.
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Results
A 250 mH inductor at 60 Hz power line frequency has a reactance of 94.25Ω. Connected to 120V, it would draw about 1.27 A of current.
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Results
A 0.1 mH (100 µH) RF choke at 1 MHz has a reactance of 628.3Ω, effectively blocking radio-frequency signals while allowing lower frequencies to pass.
Inductive reactance (Xₗ) is the opposition an inductor offers to alternating current. It arises because a changing current through an inductor creates a changing magnetic field, which in turn induces a voltage (back-EMF) that opposes the current change. Measured in ohms, it depends on both the inductance and the frequency: Xₗ = 2πfL.
The back-EMF produced by an inductor is proportional to the rate of current change (V = L·di/dt). At higher frequencies, the current changes faster, producing a larger opposing voltage and thus greater effective opposition. Doubling the frequency doubles the inductive reactance.
At DC (f = 0), the inductive reactance is zero: Xₗ = 2π(0)L = 0. An ideal inductor has zero DC resistance and acts as a short circuit to direct current. In practice, real inductors have some DC resistance from the wire used in the coil, called DCR (DC resistance).
An ideal inductor does not consume power. It stores energy in its magnetic field during one quarter of the AC cycle and returns it to the circuit during the next quarter. The power oscillates between the source and the inductor with a time-average of zero. In practice, real inductors have wire resistance that dissipates some energy as heat.
Inductive reactance is the imaginary component of impedance. For a pure inductor, the impedance is Z = jXₗ, where j is the imaginary unit. For a series RL circuit, impedance is Z = R + jXₗ, with magnitude |Z| = √(R² + Xₗ²). The reactance determines the reactive part while resistance determines the real part.
In a purely inductive circuit, the current lags the voltage by exactly 90° (or π/2 radians). This is often remembered by the mnemonic 'ELI the ICE man'—in an inductor (L), voltage (E) leads current (I). This 90° phase shift is why inductors do not dissipate real power.
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