How the capacitor is work in electrostatic induction?

Definition: 
A capacitor is most simply defined as two conductors separated by a dielectric. It is easier to grasp the significance of this definition by looking at a commonly used model for a capacitor that is shown here. A capacitor is also called a condenser.

A dielectric is a material that is a good insulator (incapable of passing electrical current), but is capable of passing electrical fields of force.
 
Some examples dielectric materials:
vacuum  ,air  ,aluminum oxide  ,various ceramics  ,Barium titanate   ,glass  ,water  ,mica  ,oil etc .

 Charged Capacitor

A capacitor is said to be charged when there are more electrons on one conductor plate than on the other.
The plate with the larger number of electrons has the negative polarity. The opposite plate then has the positive polarity.
When a capacitor is charged, energy is stored in the dielectric material in the form of an electrostatic field.


Electrostatic Induction  
When an electron is added to one plate of a capacitor, one electron is driven away from the opposite plate.
Or you can say that when an electron is pulled away from one plate of a capacitor, another electron is drawn to the opposite plate.

No matter how you look at it, this is the principle of electrostatic induction at work in a capacitor.


When this electrostatic effect increases the imbalance of electrons between the two plates:
The electrostatic field grows stronger.
The amount of energy stored in the dielectric increases.
The capacitor is said to be charging.
When this electrostatic effect decreases the imbalance of electrons between the two plates:

The electrostatic field grows weaker.
The amount of energy stored in the dielectic decreases.
The capacitor is said to be discharging.

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