Enter your Capacitance, Resistance, Initial Voltage, and Discharge Time into the Capacitor Discharge Calculator to find the Voltage at Time, along with your circuit's Time Constant (τ), Current at Time, Initial Energy, and Energy Discharged.
Voltage at Time
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Time Constant (τ)
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Current at Time
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Initial Energy
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Energy Discharged
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Percent Discharged
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A capacitor discharge calculator determines how voltage across a capacitor decreases over time when discharged through a resistor. It's essential for safety calculations, timing circuits, and energy storage applications.
The time constant (τ) equals resistance (R) multiplied by capacitance (C): τ = R × C. After one time constant, the voltage drops to about 37% of its initial value.
After 5 time constants (5τ), a capacitor is approximately 99.3% discharged, leaving only 0.7% of the original voltage. This is considered fully discharged for most practical purposes.
Safety standards require capacitor voltage to drop below safe thresholds before human contact. Calculate discharge time needed to reach safe voltage levels using appropriate discharge resistors.
Common units are microfarads (µF) for capacitance and kiloohms (kΩ) for resistance. The calculator supports various units including picofarads, nanofarads, ohms, and megohms.
Discharge current equals the voltage across the resistor divided by resistance: I = V/R. Current decreases exponentially as the capacitor voltage drops during discharge.
Discharge rate depends on capacitance value, resistance value, and initial voltage. Larger capacitance or resistance increases discharge time, while higher initial voltage increases initial current.
Choose resistance based on desired discharge time and power handling capability. Lower resistance discharges faster but dissipates more power initially. Consider safety standards and component ratings.