RC time constant

Uncommon card · No. 176518

The RC time constant, denoted τ (lowercase tau), the time constant of a resistor–capacitor circuit (RC circuit), is equal to the product of the circuit resistance and the circuit capacitance: τ = R C . {\displaystyle \tau =RC\,.} It is the time required to charge the capacitor, through the resistor, from an initial charge voltage of zero to approximately 63.2% of the value of an applied DC voltage, or to discharge the capacitor through the same resistor to approximately 36.8% of its initial charge voltage. These percents are derived from e, the base of natural logarithms, where 63.2 % ≈ 1 − e − 1 {\displaystyle 63.2\%\approx 1{-}e^{-1}} and 36.8 % ≈ e −...

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