Thursday, October 11, 2012

What is Capacitors

A capacitor (originally known as condenser) is a device which stores electric charge. Capacitors vary in shape and size, but the basic configuration is two conductors separated by a dielectric, with a charge +Q on one conductor (typically referred to as a “plate”) and an equal but opposite charge −Q stored on the other conductor. We find that the charge stored by a capacitor is proportional to the potential difference between the two conductors. In other words, Q = CV , Where,  Q is the charge stored by the capacitor, C is the capacitance value of  the capacitor, and V is the voltage applied across the capacitor.

The capacitance of a given set of conductors depends only upon their geometry (the shape of the conductors and the distance between them) and on the “stuff” placed between them. We refer to any insulating material placed between conductors in a capacitor as a dielectric.
The SI unit of capacitance is the farad (F):  1F = 1 farad = 1coulomb / volt= 1C / V.
Normal value of  capacitance is smaller and it is measured in microfarad, nanofarad,  and picofarad.

There are three principal capacitor geometries you should become familiar with:
• the parallel-plate capacitor.
• the cylindrical capacitor.
• the spherical capacitor.

Capacitors have many important applications in electronics. Some examples include storing electric potential energy, delaying voltage changes when coupled with resistors, filtering out unwanted frequency signals, forming resonant circuits and making frequency-dependent and independent voltage dividers when combined with resistors.
The symbol for a capacitor used in schematic diagrams of electronic circuits looks very much like a parallel-plate model.

 Symptoms of faulty motherboard associated to faulty capacitors:
1) The computer does not start up from the first time, you need a lot of try on the power key.
2) Motherboard failed to complete the post , it start up but no  Data.
3) Failure to complete RAM memory test at the beginning of the run motherboard or motherboard stop at the RAM memory test.
4) The fan processor run and  front LED lighting  without giving Data on the screen.
5) When motherboard try to download the Windows OS  fails to complete the download process.
6) CPU overheating unusually Although not loaded complex operations.
7) instability of the computer, particularly when running complex graphical programs.