The time constant for the circuit, \u03c4, is the time for the voltage (or current, or charge) to decay to 1/e (\u2248 0.368) of its initial value. It is a measure of the response time for the circuit. Hence a graph of ln V vs. t will yield a straight line with slope equal to \u20131/RC = \u20131/\u03c4, as illustrated in Figure 3.
