Analyse a series RL circuit for impedance, time constant and phase angle.
The RL time constant is L divided by R, unlike RC where the two multiply. Current rises exponentially toward its steady-state value, which is limited by resistance alone once the transient has settled. Interrupting current in an inductor produces a large voltage spike, which is why freewheel diodes are fitted across relay and motor coils.
RL Circuit
Z = √(R² + X_L²); τ = L ÷ R
Z = √(R² + X_L²); τ = L ÷ R The RL time constant is L divided by R, unlike RC where the two multiply. Current rises exponentially toward its steady-state value, which is limited by resistance alone once the transient has settled.
Interrupting current in an inductor produces a large voltage spike, which is why freewheel diodes are fitted across relay and motor coils.
This calculator takes 4 inputs: Resistance, Inductance, Signal frequency, Supply voltage. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.