CAPACITOR

A capacitor is a device or arrangement used to increase the capacitance of a conductor without increasing the size of the conductor but bringing another earthen conductor near it. Two conductors separated by an insulated material used to separated by an insulated capacitor. The insulated material used to separate the metal plates is called the dielectric material or in short dialectic.For example:two parallel metal plates separated by mica forms capacitor . charged cloud and earth's surface separated by air forms a capacitors,
FORMATION OF CAPACITOR :Supposed two metal A and B is arranged as shown, the arrange segment is made to increase the capacitance of the conductor . A without changing the size of the conductor of a capacitor . Let us supposed A and B is separated by an insulated dielectric material. The arrangement will increase the capacitance of the metal plate A. The second plate B is always earthen.It can be shown as given below.
When the conductor B is kept near a positively charged conductor A then it induces opposite charges inside the plate B as shown.Similarly induce similar positive charge on outside B will be neutralized by the charges from the earth. The induced negative charge inside the plate B decreases the amount of force to be applied to carry an unit positive charge from infinity to the plate that plate A is the electrical potential v of the plate. Hence charged . As the potential decreases the capacitance c = q/v must be increased .
Thus the presence of the earthen metal plate B near the conductor A increases the capacitance of the metal plate A. The metal plate A and B forms an electric device called the capacitor .
The function of such formed capacitor is to increase the capacitance of the capacitor so as possible to store charges on them.

Thus every capacitor contains two conductors one charged, other earthen and separated by an insulator known as dielectric, thus formed capacitors are used to store the electric charged.