How capacitor works ?

The capacitor works on the principle that whenever a earthed conductor is brought near a capacitor then their is increase in capacitance of a conductor.

Let us consider a parallel plate capacitor with a dielectric between them.When we will apply some voltage V or a battery is connected to a capacitor then the electric field is developed across the dielectric and the positive charge will deposit at plate 1,negative charge will deposit at plate 2.

When these plates are applied with the voltage they will carry positive charge from the battery at plate 1 and negative charge on plate 2. For some time the voltage is applied and within that time the capacitor gets charged to the maximum limit of holding charge and this time is called as charging time of the capacitor.

After some time when the capacitor has reached its maximum limit of charging then we will cut the supply of power to the capacitor. For a certain time, the two plates hold a negative and positive charge. Thus, the capacitor acts as a source 

If these plates are connected to a load, the current flows through the load from plate 1 to plate 2 until all the charges are dissipated from both plates. This time of discharging of the capacitor is known as the time of dissipation.

Capacitance is ratio of electric charge on each plate (conductor) to the potential difference.The SI unit of capacitance is Farad.