What is the term for the time required for the capacitor in an RC circuit to be charged to 63.2% of the applied voltage or to discharge to 36.8% of its initial voltage?
Why In an RC circuit the voltage across the capacitor changes exponentially, and the characteristic time of that exponential is the time constant, tau = R times C (in an RL circuit tau = L/R). After one tau the capacitor has charged to 1 - 1/e = 63.2% of the applied voltage, or discharged to 1/e = 36.8% of its starting voltage. After about five time constants the circuit is considered fully charged or discharged.
Watch out The other choices are invented phrases; there is no standard quantity called an exponential period or a time factor in RC analysis.
63.2% up, 36.8% down = one time constant. Tau = R x C, and 5 tau means done.