History of Capacitor

	Revision 6 . . (edit) October 3, 2001 10:10 pm by Tezcatlipoca
	Revision 5 . . September 28, 2001 10:57 pm by Soam Vasani [1/frequency is not wavelength, corrected resonant freq. formula]
	Revision 4 . . September 28, 2001 8:47 am by (logged).35.185.xxx

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Difference (from prior major revision) (minor diff, author diff)

Changed: 1c1

A capacitor is a device that stores elecrical charges. A capacitor consists of two conductive plates at different electrical potentials, and an insulating dielectric or insulator. The size of the charge that a particular capacitor can hold is:

A capacitor is a device that stores electrical charges. A capacitor consists of two conductive plates at different electrical potentials, and an insulating dielectric or insulator. The capacitor's capacitance (C) is a measure of how much voltage (V) appears across the plates for a charge (Q) stored in it:

Changed: 3c3

C = Eo * K * L * W / D

C = Q / V

Changed: 5,7c5

where C is the capacitance in Farad?s, Eo is the electrostatic permittivity of vacuum or free space, K is the value of the dielectric or insulator used, and L, W, and D are the length and width of the common surface, and the distance between the plates. For electronic devices such as radios, the frequency tuning is a combination of capacitance and inductance in the formula:

A capacitor has a capacitance value of one farad when one coulomb of charge causes a potential difference of one volt across the plates. Since the farad is a very large unit, values of capacitors are usually expressed in microfarads or picofarads.

Changed: 9c7,17

1/ frequency = wavelength = C * I

The size of the charge that a particular capacitor can hold is: C = Eo * K * A / D where C is the capacitance in farads, Eo is the electrostatic permittivity of vacuum or free space, K is the dielectric constant of the insulator used, A is the area of the each of the two plates, and D is the distance between the plates. For electronic devices such as radios that select a particular frequency, the frequency selected is a function of the inductance (L) and the capacitance (C) in series, and is given by f = 1/(2 * pi * sqrt(L * C)) This is the frequency at which resonance? occurs in a series RLC circuit.

Changed: 13c21

Capacitors block DC, but allow AC to pass through. The amount of "resistance" of a capacitor to AC is known as capacitive reactance, and varies depending on the AC frequency. Capacitive reactance is given by this formula:

The amount of "resistance" of a capacitor to AC is known as capacitive reactance, and varies depending on the AC frequency. Capacitive reactance is given by this formula:

Added: 22a31,35

It is called reactance because it reacts to change in the value of the current. Since the reactance is inversely proportional to the frequency, capacitors completely block direct current, and for high frequency alternating currents the reactance is small enough to be considered as zero in approximate analyses.