# Capacitor

• 12-04-2001
gnu-ehacks
Capacitor
This is an electronics question. What does a capacitor do?
• 12-05-2001
SilentStrike
Stores charge.

E&M is the devil :(.
• 12-05-2001
It also has the useful property of conducting an alternating current but effectively being a short circuit to a dc signal. Thus between stages in an analog amplifier for example, the dc signal can be passed on, but the dc conditions required for operation of the stages are isolated.
• 12-05-2001
novacain
Explodes loudly when you turn your PC on one morning.

(Or are my co-workers booby-traping my PC?)
• 12-06-2001
doubleanti
can change tone of your guitar's pickup signals when different rated caps are applied to the pots...
• 12-06-2001
>>> can change tone of your guitar's pickup

This is an effect of the property I described earlier, the AC signal frequency range passed by a capacitor is a function of it's value. Before the days of digital signal processing, phase locked loops and so on, capacitors, (with some coils/chokes and resistors), were used as signal filters, loudspeaker crossovers, etc.
• 12-06-2001
Trance
A capacitor is mainly used to store charge for a certain period of time (depending on how big your capacitor is). It is constructed by two parallel conductive plates. These plates are seperated by an insulating material called 'dialectric'. A capacitor can have 3 different states:
1. Neutral - equal number of electrons on each plate.
2. Charging - electrons are removed from one plate and put on the other.
3. Charged - voltage of the capacitor is equal to the voltage source.

A few other things to know about capacitors...
When a capacitor is charged, you can take it out of a circuit and it keeps it's charge, in other words, if it's charged, DON'T TOUCH IT! :) Capacitance is related to Charge and voltage...

C = Q/V
C = capacitance, Q = coulomb (of charge), and obviously V = voltage.
In schematics, capacitors look like this...

------| (------
• 12-06-2001
I use

----| |---- for bipolar

----| []---- for polar, (electrolytic, Tantalum bead)

>>> if it's charged, DON'T TOUCH IT!

Certainly not if it's a big one! zzzzZZZZZapppp!!!

*** EDIT ***

Actually, talking of Tantalum beads reminded me of a certain electronics engineer at an old company of mine who, once a year, employed a bunch of students for work experience. After a few days, he would give them a bit of Vero board and a handful of components and get them to solder them to the baord to see how well they could handle an iron.

Something he always did was to grab a packet of "Smarties", (I don't know if you have them wherever you are, they are small blobs of chocolate covered in a brightly coloured crunchy coating). He would use a Dremmel to make a couple of small holes in each and using a hot wires, melt a couple of wires into the chocolate, and issue these in the component packs. (Those of you who know what a Tantalum bead capacitor looks like are now way ahead of me!).

Anyway, when called to present their work, he would, as he inspected the boards, pick the "Tantalum beads" off and eat them much to the consternation of the student!!