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Capacitor discharging

Transients · Intermediate · about 15 minutes · part of Zen’s Electronics Design Mastery

A charged capacitor emptying through a resistor decays exponentially toward zero. It loses 63 % of its voltage every time constant.

Capacitor discharging: the circuit on the simulator's bench

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How it works

τ = Rd · C = 4.7 s

VC(t) = V0 · e−t/τ, I(t) = (V0 / Rd) · e−t/τ

After 1τ: 36.8 % left. After 5τ: 0.7 % left. The scope’s 1 MΩ input sits in parallel with Rd, so the bench decays about 1 % faster.

Try it on the bench

  1. Click the changeover switch S to B. The capacitor discharges through R_d.
  2. Click it back to A to recharge in a fraction of a second through the 100 Ω resistor.

Parts on the bench

In the course

Zen’s Electronics Design Mastery, module “Capacitors, Inductors & Time”.

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