Work out rl time constant instantly with clear inputs, formula shown and shareable results.
In an RL circuit the time constant is L/R, and current rises as I(t) = (V/R)(1 - e^(-t/tau)). Note that more resistance makes the circuit faster, the opposite of RC, because resistance limits the final current the inductor must build up to.
RL time constant
tau = L / R; I(t) = (V/R)(1 - e^(-t/tau))
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.
Because the final current is lower, so less flux has to be established. The rate of change dI/dt = V/L is unchanged at the start.
Interrupting the current forces dI/dt to a huge value, and V = L dI/dt produces a destructive voltage spike unless the current has somewhere to go.