Capacitors

Capacitors have 3 primary functions:

1. To store a charge, much like a battery. These capacitors are normally
electrolytic and are used in situations like power supplies where a
fluctuating DC voltage needs to be smoothed, or, have the ripple taken out.

2. A capacitor is used to block DC while allowing AC to pass through such
as in an audio amplifier where we are passing the audio signal through from
one stage to the next.

3. To counteract inductive reactance in order to create a "tuned circuit".

4. A cap can also be used as a spike filtering, which is slightly different than smoothing an AC signal. The term for this purpose is "bypass cap" in case anyone out there was wondering about that one.

When power gets to them they hold a charge right away, but will eventually discharge if left alone or you can discharge a capacitor by hitting both of it's leads together or connect a resistor between both leads.  Capacitors have different levels, which are specified in farads.  Below are common schematics symbols for capacitors and common farad ratings.

1-Farad = 1F 1-Microfarad = 1mF or uF = .000001F 1-Picofarad = 1pF - .000000000001F

C1 shows a normal fixed capacitor, these you can connect in like resistors.  C2 shows one that is polarized, this means you must connect it's positive lead the most positive connection point in it's placement. With polarized capacitors you'll mind that they are marked with either a plus to show the positive side or with a negative to show the negative side.  C3 shows a variable capacitor, I have yet to see one of these in a circuit.

Capacitors are not color-coded but they do have a numbering system that tells you what their value is.  This can be tricky to find the value of an odd capacitor but most of the time you'll see number like this: 151K  The first and second digits are the capacitors value.  For the third number find it's multiplier value on the chart to the left and simple multiply.  So 151K is a 150pF capacitor.  You might also see a notation like this, EG 104 or 104K both of which are .1uf caps.  Caps, of course here is short for capacitor.

The letter tells you the tolerance of the cap, you can look up the tolerance on this chart.  A note I want to add to this capacitor section is that sometimes you may see the letter R on a cap, which would signify a decimal point.  So if you see 2R2 that would equal 2.2 (pF or uF).  My best advice is to keep your capacitors well organized and with their packaging if you are not confident you can distinguish one capacitor from another.

An important thing to take notice of is that capacitors DO NOT add in series like resistors, just the opposite, two 1mfd capacitors in series equal 0.5 mfd.