ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1
Given:
Percent of charge = 20% (.20)
T = 100 microseconds
R
= 20,000 Ohms
Transpose the RC time constant formula as follows:
R x C = RC
R C
C = _
R
Find: HC
.22 RC = 100 microseconds
100 microseconds
RC =
.22
RC = 455 microseconds
Substitute the R and RC values into the formula:
R C
C = _
R
455 microseconds
C =
20,000 Ohms
C = .023 microfarads
The graphs shown in figures 36 and 37 on pages .57 and 58,
respectively, are not entirely correct. That is, the charge
or discharge (growth or decay) will not quite complete in 5 RC
or 5 L time constants. However, when the values reach 0.99
R
of the maximum (corresponding to 5 RC or 5 L), the graphs may be
R
considered accurate enough for all practical purposes.
k. Capacitors in Series and Parallel. Capacitors may be
(connected in series or in parallel to obtain a resultant value
which may be either the sum of the individual values (in
parallel) or a value less than that of the smallest capacitance
(in series).
(1) Capacitors in Series. The overall effect of connecting
capacitors in series is to move the plates of the capacitors
further apart. This is shown in figure 39 on the following
page. Notice that the junction between C1 and C2 has both a
negative and a positive charge. This causes the
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