Charging of Capacitor RC Time

Electric circuit of resistor and capacitor connected in series with switch (S), elemental resistor (R), capacitor (C), and battery (B). 

In addition, a relation of the charge time to the current traveling through the circuit can also be derived by taking the derivative of q with respect to t in Equation (1.25) as shown by 

In all these equations, the RC product is the capacitive time constant and is represented by t, (= RC). For example, when t = r = RC, Equation (1.25) is reduced to q = 0.63Cy , indicating that at f = x, = RC, only 63% of the total charge can be achieved given the driving potential. For general purposes, a capacitor is considered to have a full charge after five time constants. 

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