applied voltage at the end of this time. At the instant E is

applied, t and Ec are equal to zero; current and ER equal 100 percent

of their maximum values. When t is 1 usec, onetenth of 1 time

constant has elapsed. At this time, Ec is equal to 10 percent of the

applied voltage or 0.1 volt, ER, is equal to 90 percent of the

applied voltage or 0.9 volt, and It is equal to 90 percent of its

maximum value or 0.09 mA. The values of Ec, ER, and It in Table III

are obtained from the universal time constant chart.

Table III. Voltage and current values when a positive DC

is applied to a series RC circuit

c. After 70 usec, 7 time constants have elapsed. Ec then is

equal to 1 volt, and ER and It are equal to zero. The approximate

current flowing in any series RC circuit and the voltage across the

components in the circuit can be determined by substituting the

appropriate values of E, R, and C in the circuit.

13.

STEPBYSTEP PROCEDURE FOR DETERMINING TRANSIENT RESPONSE

a. When a universal time constant chart is unavailable, the

response curve of any RC circuit can be approximated by using the

basic voltage equation E = ItR + Q/c. Since Q/C = Ec, the formula

may be expressed as E = It R + Ec. The following stepbystep

procedure is used to provide an approximate response of a series RC

circuit to any waveform.

b. In this procedure, assume that the current does not decrease

continuously, but rather, in small steps. In a series RC circuit,

let E equal 1 volt, C equal 1,000 uuf, and R equal 10,000

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