what is a capacitor

[Faisal__saf]

dear friends
:arrow: what is a capacitor
what doec it do :?:
when it is used
why it is used
what is its function
what changes it make to a wave form
what will happen if we connect it in parellel or in series :?:
if any body knows or could give me a best link to learn step by step
please send me an e-mail
faisal__saf@hotmail.com
or reply here in electro tech on..

 

[Ravi]

In general terms a capacitor is an arrangement of conductors that are insulated from each other so that charge can be stored. We can regard the capacitor as a device which receives electricity when it is charged and stores it until it is discharged.

Imagine two metal plates arranged parallel to each other & spearated by air. If we apply a voltage to the plates by connecting them to a battery then one plate will gain electrons and the other will lose electrons. Now whe the battery removed ther is no connection betwen the plates, that would allow the electrons to return, and there will still be a voltage between the plates, caused by the fact that one plate is negatively charged and the other positively charged. This arrangement is a capacitor. If the plates are now connected, a transient current will flow until there is no surplus or deficit of electrons on either plate.

The quantity of electricity stored for a given voltage between the plates is a measure of their capacitance. The unit of capacitance is the Farad, named after Michael Faraday, the discoverer of electromagnetic induction.

The farad is too large for most practical purposes, though caps of 1 farad or more are available for specialised purposes. The usual, largely used, sub-division for the farad is microfarad.One million microfarads equal 1 farad. Other sub-multiples are nanofarad and picofarad.

Caps can be connected in series or in parallel. When they are in parallel, the total capacitance is found by adding the individual capacitances together. When connected in series, if they are of equal capacitance, the joint capacitance is found by dividing the capacitance of one of them by the number of capacitors. If they are not equal, the procedure is the same as for resistance in parallel.

Another point is that the larger capacitors can store a considerable amount of charge at a voltage level which can cause severe shock or burning if the terminals are touched. Even at low voltages, the amount of energy stored by a capacitor can cause destructive sparking, sufficient to melt even metal wires,if a charged cap is short circuited.