A capacitor is a device that is used to store charges in an electrical circuit.
A capacitor works on the principle that the capacitance of a conductor increases appreciably when an earthed conductor is brought near it.
Hence, a capacitor has two plates separated by a distance having equal and opposite charges.
The space between the conductors may be filled by vacuum or with an insulating material known as a dielectric. The ability of the capacitor to store charges is known as capacitance.
Equation of capacitance is given by,
Working principle of a capacitor:
Consider the following circuit, which shows the working principle of a parallel plate capacitor with a dielectric between them.
Apply the voltage V as shown in the circuit, with plate 1 being positive and plate 2 being negative. An electric field appears across the capacitor.
When the voltage is supplied to these plates, plate 1 will carry a positive charge from the battery, and plate 2 will carry a negative charge from the battery.
The voltage is supplied for a period of time, during which time the capacitor is charged to its maximum holding charge, and this period is referred to as the capacitor's charging time.
After a period of time, when the capacitor has reached its full charging capacity, we will turn off the electricity to the capacitor. The two plates have a negative and positive charge for a period of time.
As a result, the capacitor serves as a source of electricity. If these plates are connected to a load, current flows from plate 1 to plate 2 until all charges on both plates have been dissipated.
The time it takes for the capacitor to discharge is referred to as the dissipation time.