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Discharge Time Formula:
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The discharge time formula calculates the approximate time it takes for a capacitor to discharge through a resistor. The formula t = 5 × R × C represents approximately 5 time constants (5τ), at which point the capacitor is considered almost fully discharged (to about 0.7% of its initial voltage).
The calculator uses the discharge time formula:
Where:
Explanation: The time constant τ = R × C represents the time it takes for the capacitor to discharge to about 36.8% of its initial voltage. After 5 time constants, the capacitor is considered effectively discharged.
Details: Calculating discharge time is essential for designing timing circuits, power supply systems, and any electronic application where controlled discharge of capacitors is required for proper circuit operation.
Tips: Enter resistance in ohms and capacitance in farads. For values in different units (kΩ, mF, μF, nF, pF), convert to base units before calculation. All values must be positive numbers.
Q1: Why is 5 time constants used for discharge time?
A: After 5 time constants, the capacitor voltage drops to about 0.7% of its initial value, which is considered effectively fully discharged for most practical purposes.
Q2: How do I convert between capacitance units?
A: 1F = 1000mF = 1,000,000μF = 1,000,000,000nF = 1,000,000,000,000pF. Make sure to convert to farads before calculation.
Q3: Does this formula work for both charging and discharging?
A: This specific formula (t = 5RC) is for discharge time. The charging time to approximately 99.3% of the source voltage is also 5 time constants.
Q4: What factors can affect actual discharge time?
A: Temperature, capacitor leakage, resistor tolerance, and the capacitor's equivalent series resistance (ESR) can all affect actual discharge times.
Q5: Can this calculator be used for AC circuits?
A: This calculation is specifically for DC RC circuits. AC circuit analysis requires different approaches considering frequency and impedance.