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RC circuit discharging
Intermediate
Capacitor voltage decays exponentially.
V = V₀e^{−t/RC}A charged capacitor discharges through a resistor: V = V₀e^{−t/RC}. After 5RC it has fallen to 0.7%.
Camera flash discharge.
Current direction reverses compared to charging.
In more detail
When a charged capacitor discharges through a resistor, its voltage falls exponentially to zero. The current flows in the opposite direction to charging.
Real-world uses
- Flash units discharge capacitors to produce bright light.
- Timing and pulse circuits use controlled discharge.
- A capacitor in a flash unit discharges through the lamp, producing a brief, bright pulse of light.
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Frequently asked questions
What is the discharge equation?
V = V0 e^(−t/RC).
Can a discharged capacitor shock?
Large capacitors can hold dangerous charge even after power is removed, so care is needed.
Why does the voltage fall quickly at first?
The current is largest at the start, when the voltage across the resistor is greatest, so the capacitor loses charge rapidly.
Related topics in Current Electricity & Circuits
Superposition theorem · Delta–star conversion · RC circuit charging · Time constant · Current in RC circuit · Capacitor networks