Capacitor and capacitance | Fixed Capacitors

A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. OR capacitor or condenser, device for the storage of electric charge.

Simple capacitors consist of two plates made of an electrically conducting material (e.g., a metal) and separated by a non-conducting material or dielectric (e.g., glass, paraffin, mica, oil, paper, tantalum, or air). 
If an electrical potential (voltage) is applied to the plates of a capacitor (e.g., by connecting one plate to the positive and the other to the negative terminal of a storage battery), the plates will become charged, one positively and one negatively.

If the externally applied voltage is then removed, the plates of the capacitor remain charged, and the presence of the electric charge induces an electrical potential between the plates.

It is given by,

C: Capacitance of capacitor in farad

A: Area of any one plate in m²

D: Distance between two plates in m

ε: Permittivity of material = ε₀ε_r

ε_0: Absolute permittivity = 8.854X10-¹² farad/meter

ε_r: Relative permittivity

The capacity of the device for storing electric charge (i.e., its capacitance) can be increased by increasing the area of the plates, by decreasing their separation, or by changing the dielectric. The dielectric constant of a particular dielectric is the measure of the dielectric’s unit capacitance.