Charging and Discharging a Capacitor.

Electronic Principles
Page Navigation
48

g. Charging and Discharging a Capacitor.

(1) Charging. In order to better understand the action of a

capacitor in conjunction with other components, the charge and

discharge actions of a purely capacitive circuit are analyzed

first. For ease of explanation the capacitor and voltage source

shown in figure 31 are assumed to be perfect (no internal

resistance), although this is impossible in practice.

FIGURE 31. CHARGING A CAPACITOR.

In figure 31, view A, an uncharged capacitor is shown connected

to a fourposition switch. With the switch in position 1 the

circuit is open and no voltage is applied to the capacitor.

Initially each plate of the capacitor is a neutral body and

until a difference of potential is impressed across the

capacitor, no electrostatic field can exist between the plates.

To CHARGE the capacitor, the switch must be thrown to position

2, which places the capacitor across the terminals of the

battery. Under the assumed perfect conditions, the capacitor

would reach full charge instantaneously. However, the charging

action is spread out over a period of time in the