A capacitor is an *electronic* device that stores electrical energy in an electric field. The effect of a capacitor is known as Capacitance. The capacitor passes alternating current instead of passing direct current. A capacitor consists of terminals that possess voltage values that can be either positive or negative.

Capacitors are of different types like; *electrolytic capacitor, mica capacitor,* paper capacitor, film capacitor, ceramic capacitor.

The capacitance of a capacitor is measured in unit farads(F).

## Theories Of Operation Of Capacitor

A non-conductive region separates the two conductors of a capacitor. The non-conductive region can be anything, like a vacuum or an electrical insulator known as a dielectric.

According to Coulomb’s Law, a charge from one conductor exerts a force on the charge carrier of the other conductor, which attracts opposite polarity charges, and repels polarity charges. Therefore, an opposite polarity charge is held on the surface of another conductor. Now both the conductors hold equal and opposite charges, and thus an electric field is created.

A capacitance of one farad equals the one-coulomb charge on each conductor causes one volt of voltage across the device.

** C = Q/V**

In some situations, the created electric field and the charge build-up causes the capacitance to vary. So, they are known as the incremental changes in the capacitance-

**C = dQ/dV**

**Hydraulic Analogy**

Charge carriers, which flow through a wire are analogous to water flowing through a pipe. A * capacitor* is like a rubber membrane sealed in a pipe. However, water molecules don’t pass through the membrane, but a little amount of water can move by stretching it.

### Circuit at short time and long time limit.

In long time limits, after discharging current saturates the circuit, no amount of current can come on either side of the capacitor.

In short time limits, the capacitor starts with a certain voltage, and when voltage drops, it can be replaced with an ideal voltage source.

#### Parallel Plate Capacitor

A parallel plate capacitor can only store a limited amount of energy before dielectric breakdown. The strength of the dielectric material sets the capacitor’s breakdown voltage. The maximum energy is a function of dielectric strength, dielectric volume, and permittivity.

#### Interleaved Capacitor

The interleaved plates are the parallel plates, which are connected. Every pair of adjacent plates acts as a separate capacitor. The number of pairs is one less than the number of plates.

#### Increasing Charge

To increase capacitors charge and voltage, an external power source is required to do the work to move the charge from negative to positive against the opposing force.

#### Current-Voltage Relation

The current is defined as the rate of flow of charge, which passes through it, but the actual charge is the electron that cannot pass through the dielectric layer. One electron is accumulated on the negative plate, for that electron, which leaves the positive plate, thus resulting in an electronic depletion.

**Laplace Circuit Analysis**

According to the Laplace Circuit Analysis, the impedance of an ideal capacitor with no initial charge is represented as,

Z(s) = 1/sC

Here, C is capacitance, and s is complex frequency.