capacitors

Generality

The capacitor is an electric component capable of storing electrical energy and restore it during its discharge.

It is composed of two metal plates called armatures placed facing one another and separated by an insulator called dielectric variable thickness.

When applied between two plates of a capacitor voltage U, it accumulates two opposite charges + Q and -Q.
In all capacitors, C = Q / U ratio is whatever the value of Q and U, this report is called the capacitance of the capacitor. It measures the property of a capacitor storing Q amount of electricity at a given voltage. More this capacity is more large energy stored in a given voltage is large:

C: amount of a capacitor in F
Q: amount of electricity C
U: voltage V
The capacitance of the capacitor can also be expressed by the relationship C = E0 + Er.S / e; E0.Er = E, with:

E0: vacuum permittivity; E0 = 8,85x10-12
Er: relative permittivity of the dielectric constant or the dielectric
S in m2: area frames
e m: thickness or distance between the two plates.
For a driver capacitance C having a voltage U across its terminals, the stored energy W is given by the relation W = ½.C.U2, with:

W: J
C: F
U: V

Association of capacitors
Serial

In parallel