Calculate inductor stored energy, inductive reactance, and time constant from inductance and current.
Inductive reactance (XL) is the opposition an inductor presents to AC current. Unlike resistance, it increases with frequency: XL = 2πfL. At DC (0 Hz), an ideal inductor has zero reactance.
The RL time constant τ = L/R determines how fast current builds up or decays in an RL circuit. After one time constant, current reaches 63.2% of its final value. After 5τ, it's essentially at steady state.