Capacitor

CAPACITOR

A capacitor is a device which stores electric charge. Capacitors vary in shape and size, but the basic configuration is two conductors carrying equal but opposite charges (Figure 5.1.1).Capacitors have many important applications in electronics. Some examples include storing electric potential energy, delaying voltage changes when coupled with resistors, filtering out unwantedfrequency signals, forming resonant circuits and making frequency-dependent and independent voltage dividers when combined with resistors.



In the uncharged state, the charge on either one of theconductors in the capacitor is zero. During the charging process, a charge Q is moved from one conductor to the other one, giving one conductor a charge +Q, and the other one a charge -Q. A potentialdifference ∆V is created, with the positively charged conductor at a higher potential than the negatively charged conductor. Note that whether charged or uncharged, the net charge on the capacitor as a wholeis zero.
The simplest example of a capacitor consists of two conducting plates of area A, which are parallel to each other, and separated by a distance d, as shown in Figure 5.1.2.


Experiments showthat the amount of charge Q stored in a capacitor is linearly proportional to ∆V, the electric potential difference between the plates. Thus, we may write:
q = C | ∆V |
where C is a positiveproportionality constant called capacitance. Physically, capacitance is a measure of the capacity of storing electric charge for a given potential difference ∆V. The SI unit of capacitance is the farad (F):
1F = 1 farad = 1 coulomb / volt = 1 C / V
A typical capacitance is in the picofarad (1 pF = 10-12F) to millifarad range, (1 mF = 10-3 F = 1000 µF; 1 µF = 10-6 F).

Puede definirse entoncesla capacitancia de un circuito como la propiedad de oponerse a cualquier cambio de voltaje y puede compararse a la inductancia, que es la propiedad de oponerse a cualquier cambio en la corriente, es...