Inputs
Result
Enter values and click Calculate to see results.
Theory & Derivation
For a step input applied to a series circuit, the current rises as i(t) = Ifinal(1 − e−t/τ) with τ = L/R. The half‑rise time t50% satisfies 1 − e−t/τ = 0.5 → e−t/τ = 0.5, hence t = τ ln 2 ≈ 0.693 τ.
This same factor applies to the voltage across the resistor (proportional to current). The inductor voltage decays from its initial value and does not use the same expression for “rise.”
FAQs
Provide inductance L and resistance R. The calculator converts common prefixes automatically and returns the half‑rise time in multiple units.
For first‑order timing, no. The step amplitude sets the final value but cancels out of the time expression; timing depends only on L and R.
The formula t50%=τ ln2 assumes a step change. For periodic drive, ensure the pulse width is long compared with τ or use transient simulation.
τ=L/R is the time constant; t50% is the time to reach half the final value. They are related by t50%≈0.693τ.
Yes. Choose the target in the dropdown to compute R from L and t50%, or L from R and t50%.
Results assume ideal components and a simple series path. Parasitics, core nonlinearity, temperature, and wiring resistance can shift the effective τ.
Extremely small τ may push into nanoseconds where layout matters; very large τ may require long measurement windows. Use units that keep numbers well‑scaled.