MM0704, Lesson 1
As an example of the time constant, let the voltage across the capacitor in figure 1-14A be represented by the graph in
figure 1-14B.
Figure 1-14. RC Time Constant.
When t = TC (one time constant), EC = 63.2 percent of E.
When t = 2TCs (two time constants), EC = 63.2 percent of E + 63.2 percent of the remaining applied voltage after one
time constant. That equals 0.632E + 63.2 percent of 0.368E which is 86.5 percent of E.
When t = 3TCs (three time constants), the capacitor will have acquired another 63.2 percent of the remaining applied
voltage or 95.1 percent of E.
When t = 4TCs, E = 98.2 percent of E and after 5 TCs, EC = 99.3 percent of E. Thus, for practical purposes, the
capacitor may be considered fully
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