RL time constant:
Aτ = L/R (current rises to 63% after τ during step input)
BR + L
CR × L
DR/L
Answer & Solution
Correct answer: A. τ = L/R (current rises to 63% after τ during step input)
RL: τ = L/R. Step response: i(t) = (V/R)(1 - e^(-Rt/L)). After τ: 63% of final. Diodes across inductors dissipate stored energy when supply switches off (prevent voltage spikes from L di/dt).
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