- Capacitor Definition: A capacitor is a basic electronic component that stores electric charge in an electric field.
- Basic Structure: A capacitor consists of two conductive plates separated by a dielectric material.
- Charge Storage Process: When voltage is applied, the plates become oppositely charged, creating an electric potential difference.
- Capacitance Definition: Capacitance is the ability of a capacitor to store charge per unit voltage.
- Factors Influencing Capacitance: Capacitance depends on the plate area, the distance between plates, and the dielectric material’s permittivity.
What is a Capacitor?
Capacitors are one of the three basic electronic components, along with resistors and inductors, that form the foundation of an electrical circuit. In a circuit, a capacitor acts as a charge storage device. It stores electric charge when voltage is applied across it and releases the charge back into the circuit when needed.
A basic capacitor is made of two parallel metal plates separated by a dielectric material.
When we connect a voltage source across the capacitor, the conductor (capacitor plate) attached to the positive terminal of the source becomes positively charged, and the conductor (capacitor plate) connected to the negative terminal of the source becomes negatively charged.
The dielectric between the plates prevents charges from directly moving from one plate to the other.
This creates a difference in charge levels between the two plates, leading to an electric potential difference across them.
The charge accumulation in the capacitor plates is not instantaneous rather it is gradually changing.
The voltage appears across the capacitor exponentially rises untill it becomes equal to that of the connected voltage source.
What is Capacitance?
Now we understand that the charge accumulation in the conductors (plates) causes the voltage or potential difference across the capacitor. The quantity of charge accumulated in the capacitor for developing a particular voltage across the capacitor is referred to as the charge holding capacity of the capacitor.
We measure this charge accumulation capability of a capacitor in a unit called capacitance. The capacitance is the charge gets stored in a capacitor for developing 1 volt potential difference across it.
Hence, there is a direct relationship between the charge and voltage of a capacitor. The charge accumulated in the capacitor is directly proportional to the voltage developed across the capacitor.
Where Q is the charge and V is the voltage.
Here C is the constant of proportionality, and this is capacitance,
The capacitance depends upon three physical factors, and these are the active area of the capacitor conductor (plates), the distance between the conductors (plates) and permittivity of the dielectric medium.
Here, ε is permittivity of the dielectric medium, A is the active area of the plate and d is the perpendicular distance between the plates. 
