Capacitor charge and discharge
The process by which a capacitor accumulates or loses electrical charge. During charging through a resistor, Q(t) = Q₀(1 - e^(-t/RC)). During discharging, Q(t) = Q₀e^(-t/RC) where RC is the time constant τ.
Formula
Q(t) = Q₀e^(−t/RC)
Real World
The automatic flash recycling in a DSLR camera charges a capacitor through a resistor; the photographer must wait roughly 5τ seconds before the flash is ready to fire again at full power.
Exam Focus
Always show your substitution into Q = Q₀e^(−t/RC) before rearranging — 'show that' questions require every step to earn full marks.
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