The capacitor is a common electronic device that acts like a little storage battery.
Capacitors are usually represented by the letter "C" in schematics.
A capacitor usually consists of 2 parallel plates of metal separated by an insulator as shown in the symbol.
If a DC voltage or DC current is applied to the terminals of the capacitor, it will become charged.
Electrons will collect on one plate, making it negative. The other plate becomes positive.
The opposite potentials are attracted to each other, so the capacitor has a tendancy to hold a charge.
As the charge (number of electrons) increases on a capacitor, the voltage across the terminals increases.
The voltage on a capacitor is therefore the integral (sum over time) of the current.
If the terminals of a capacitor are shorted together, the capacitor will discharge back to zero volts.
The property of a capacitor to hold charge is called "capacitance". Bigger capacitors hold a bigger charge.
The more charge that a capacitor can hold at a given voltage; the greater the capacitance.
Most capacitors are bi-polar (or non-polarized); they can hold a charge in either direction.
Electrolytic capacitors are polarized; they can only be charged in one direction.
Capacitors are available in different sizes (capacitances). The unit of measure of size is the Farad.
Non-polarized capacitors usually range in size from 100 pf (picofarads) to 1 uf (microfarad).
Non-polarized capacitors are usually used in analog circuits for filtering and signal-shaping.
Electrolytic capacitors are usually larger and range in size from 1 uf to 10,000 uf.
Electrolytic capacitors are usually used to smooth the output of DC power supplies.
Capacitors are often used to "impeade" or control the flow of electricity (as are resistors).
The impeadance of a resistor is equal to its resistance and is the same at all frequencies.
The impeadance of a capacitor is inversely proportional to the capacitance and to the frequency.
Impeadance = 1/(2*Pi*capacitace*frequency)
(where "Pi"= 3.1416 ; capacitance is Farads ; frequency is cycles per second or Hertz)
