Visualise RC and RL charging/discharging curves; find time constants and settling times
When a voltage step is applied to an RC or RL circuit, the energy-storage element prevents an instantaneous change — the response follows an exponential curve governed by the time constant τ.
τ = R × C (seconds). At t = τ: capacitor charges to 63.2% of final voltage. At t = 5τ: 99.3% — considered fully charged. Discharge: V(t) = V₀ × e^(−t/τ).
τ = L/R. Current rises to 63.2% of Ifinal in one τ. Inductor current cannot change instantaneously — switching off without a freewheeling diode generates a large voltage spike (V = L × dI/dt).