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RC Discharge Equation:
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The RC discharge time constant (approximately 5 tau) represents the time it takes for a capacitor to discharge to about 0.7% of its initial voltage through a resistor. It's a fundamental concept in electronics and circuit analysis.
The calculator uses the RC discharge equation:
Where:
Explanation: The factor of 5 represents approximately 5 time constants (5τ), which is the time required for the capacitor to discharge to about 0.7% of its initial voltage.
Details: Accurate RC time constant calculation is crucial for designing timing circuits, filter networks, and understanding capacitor discharge behavior in various electronic applications.
Tips: Enter resistance in ohms (Ω) and capacitance in farads (F). All values must be valid positive numbers. For smaller capacitance values, use scientific notation (e.g., 0.000001 = 1μF).
Q1: Why multiply by 5 in the formula?
A: The factor of 5 represents approximately 5 time constants, which is the standard duration for a capacitor to be considered fully discharged (to about 0.7% of initial voltage).
Q2: What is the relationship between time constant and discharge rate?
A: The time constant (τ = R×C) determines how quickly the capacitor discharges. A larger time constant means slower discharge, while a smaller time constant means faster discharge.
Q3: Can this calculator be used for charging time as well?
A: While the time constant is the same for both charging and discharging, the complete charging to about 99.3% also takes approximately 5 time constants.
Q4: What are typical values for R and C in real circuits?
A: Resistance values typically range from ohms to megohms, while capacitance values range from picofarads to farads, depending on the application.
Q5: How accurate is the 5-time-constant rule?
A: After 5 time constants, the voltage reaches about 0.67% of its initial value, which is generally considered "fully discharged" for most practical purposes.