Question

Is the value of the RC time constant found from discharging a capacitor through a resistor the same as the value of the RC time constant found from charging a capacitor through a resistor? Please explain.

Answer 1

For a charging CR circuit charge on the capacitor at any time t is

Q(t) = Qo{ 1 - exp ( - t/RC )}

Where RC is called time constant , the time require to charge the capacitor 63.2% Qo ,

Again considering the same circuit during discharging, Charge at any time t on the capacitor is

Q(t) = Qo exp ( - t/RC )  

Here time constant is the time at which charge on the capacitor decays

63.2% Qo i,e remaining charge on the capacitor is 36.8%Qo

Both time constant for the same RC combination has the same value.