That is, when voltage is applied to the capacitor, a charging current flows instantaneously, accumulating charge on the electrodes. When the charge to the electrode ends and the charging current decays, an absorption current flows and dielectric polarization begins. When dielectric polarization ends, a leakage current appears.
Given a fixed voltage, the capacitor current is zero and thus the capacitor behaves like an open. If the voltage is changing rapidly, the current will be high and the capacitor behaves more like a short. Expressed as a formula: i = Cdv dt (8.2.5) (8.2.5) i = C d v d t Where i i is the current flowing through the capacitor, C C is the capacitance,
Figure 8.2.1 : Basic capacitor with voltage source. The ability of this device to store charge with regard to the voltage appearing across it is called capacitance. Its symbol is C and it has units of farads (F), in honor of Michael Faraday, a 19th century English scientist who did early work in electromagnetism.
The actual DC current flowing through a capacitor consists of three elements: charging current, absorption current, and leakage current. The "pure" leakage current is not only a current that is passing through the bulk of the dielectric layer, but also bypassing between electrodes without going through the dielectric.
As mentioned above, the actual DC current flowing through a capacitor consists of three elements: charging current, absorption current, and leakage current. The role and characteristics of each element are summarized in Table 2. *16 The three components are discussed in next section.
Therefore we can state a particularly important characteristic of capacitors: The voltage across a capacitor cannot change instantaneously. (8.2.7) (8.2.7) The voltage across a capacitor cannot change instantaneously. This observation will be key to understanding the operation of capacitors in DC circuits.