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

Integrated Publishing, Inc. |