📖 Capacitor Charge/Discharge Calculator
This capacitor charge/discharge calculator helps you analyze RC circuits by calculating voltage, current, and time during capacitor charging and discharging. It's essential for timing circuits, filters, and power supply design.
📐 RC Circuit Formulas
Time Constant: τ = R × C
Charging Voltage: Vc(t) = Vf × (1 - e^(-t/τ))
Discharging Voltage: Vc(t) = Vi × e^(-t/τ)
Charging Current: I(t) = (Vf/R) × e^(-t/τ)
Discharging Current: I(t) = -(Vi/R) × e^(-t/τ)
📊 Charge/Discharge Table
| Time | Charge % | Discharge % |
|---|
| 1τ | 63.2% | 36.8% |
| 2τ | 86.5% | 13.5% |
| 3τ | 95.0% | 5.0% |
| 4τ | 98.2% | 1.8% |
| 5τ | 99.3% | 0.7% |
❓ Frequently Asked Questions
What is the time constant of an RC circuit? ▼
The time constant τ = R × C is the time required for the capacitor to charge to 63.2% of the supply voltage or discharge to 36.8% of its initial voltage. It determines how quickly the circuit responds.
How long does it take to fully charge a capacitor? ▼
A capacitor is considered fully charged after 5τ (time constants), reaching about 99.3% of the supply voltage. For practical purposes, 5τ is used as "fully charged."
What is the charging current at t = 0? ▼
At the instant of switching (t=0), the capacitor acts as a short circuit. The initial charging current is I = V/R, where V is the supply voltage and R is the resistor value.
What happens during capacitor discharge? ▼
During discharge, the stored voltage decreases exponentially. After 1τ, the voltage drops to 36.8% of the initial voltage. After 5τ, it's effectively discharged (0.7% remaining).