Inductor Calculator

Inductors are passive electronic components that store energy in a magnetic field when current flows through them. They resist changes in current, oppose AC signals while passing DC, and are fundamental building blocks of filters, oscillators, transformers, and power converters.

Inductive Reactance (XL): Reactance is the opposition an inductor presents to alternating current. Unlike resistance, it increases with frequency.

XL = 2π × f × L

Variable definitions:

• XL = inductive reactance (ohms, Ω)
• f = frequency of the AC signal (hertz, Hz)
• L = inductance (henries, H)
• π ≈ 3.14159

Energy stored in an inductor:

E = ½ × L × I²

• E = energy stored (joules, J)
• I = current through the inductor (amperes, A)

Self-resonant frequency (with parasitic capacitance C):

f₀ = 1 ÷ (2π × √(L × C))

Worked example — reactance: A 470 μH inductor in an audio crossover circuit at 5,000 Hz:

• XL = 2π × 5,000 × 0.000470 = 14.76 Ω

Compare: at 500 Hz, XL = 2π × 500 × 0.000470 = 1.476 Ω — ten times less, confirming that inductors pass low frequencies more easily than high ones.

Worked example — energy storage: A 10 mH power supply inductor carrying 2 A:

• E = ½ × 0.010 × 2² = 0.020 J = 20 mJ

Inductors in series and parallel:

• Series: L_total = L₁ + L₂ + L₃ + … (same as resistors in series)
• Parallel: 1/L_total = 1/L₁ + 1/L₂ + … (same as resistors in parallel)

Common inductor applications: power supply chokes, RF tuning circuits, EMI suppression filters, buck/boost converters, and speaker crossover networks.