5.2 Capacitor(condenser)

"A capacitor(condenser) is simply a sandwich of two metal plates separated by an insulating material."


 Although the capacitor shown above is of parallel plate type, it can come in various shapes like foils, thin films, or sintered beads of metal or conductive electrolyte. In all of these capacitors the insulating material are always sandwiched between the plates. The purpose of this nonconducting dielectric is to increase the capacitor's charge capacity or in other words to increase the capacitance. Materials commonly used as dielectrics includeglass, ceramics, platics film, papre, mica and oxide layers. In modern applications capacitors are widely used as parts of electrical circuits in electrical devices.   

 
When two conducting plates are connected to a battery electrons move towards one plate. The positive plate loses electrons as well, eventually leave both plates with equal and opposite charge, +Q and -Q. When a capacitor is charged we say that the capacitor has charge Q. Experiments shows that the amount of charged stored is proportional to the potential difference between the plates.
$$Q=C\times V$$Here, $'C'$ is the proportionality constant and is called a capacitance. $V$ is the potential difference between the plates. 

Capacitance is then defined as the ratio of the electric charge Q on each conductor to the potential difference V between them. The unit of capacitance in the (SI) is the farad (F), which is equal to one coloumb per volt $ (1 C/V)$. Capacitance values of typical capacitors for use in general electronics range from about 1 pF (10−12 F) to about 1 mF (10−3 F).
  
"1 Farad is the capacitance of a conductor, which has potential difference of 1 volt when it carries a charge of 1 coulomb."

Here's a basics of capacitor for beginers: 

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