Capacitors

Today in modern life, humans make use of many objects that have certain devices that they are not even aware of how they work or what their main function is. One of these devices that is used a lot without knowing their existence is what is called a “capacitor.” Many people have heard the word capacitor, but also many do not even have an idea of what it means or what is the use for it. In this research, I will concentrate on explaining the physics of a capacitor and describing the main types of capacitors that exist today.

A capacitor is a device used to store charge in an electrical circuit. The function of a capacitor is much similar to a battery, but it charges and discharges much more efficiently. Also, unlike a battery, a capacitor does not produce electrons; it only stores them.

A basic capacitor is made up of two conductors on which equal but opposite electric charges are placed, and an insulator, which is also called a dielectric, separates the two conductors. This dielectric could be made of paper, plastic, mica, ceramic, glass, or almost any other nonconductive material. Because each conductor stores an equal but opposite charge, the total charge in the device is always zero.

The electron storing ability of a capacitor is called “capacitance” (C), and it is measured in Farads. The capacitance (C) is a measure of the amount of charge (Q) stored on each conductor (plate) for a given potential difference or voltage (V). The formula that represents this relation is C = Q/V. In SI units, a capacitor’s capacitance is one Farad, which means one coulomb per volt.

Since the Farad is a very large unit, capacitors are usually rated in microfarads (mF=106F), nanofarads (nF=10-9F), and picofarads (pF=10-12F).

Something else that is involved with capacitors is the stored energy. When a capacitor is being charged, voltage is developed across the capacitor as a result of the electric field created by the accumulated charge. The energy, which is measured in Joules (J), is equivalent to the amount of work needed to establish the voltage across the capacitor, and thus the electric field. The energy stored is represented by the equation Estored = Ѕ*C*V2, where C is the capacitance and V is the voltage across capacitor.

Capacitors can be arranged in two different types of networks, parallel configuration and series configuration.

In a parallel configuration, each capacitor has the same potential difference or voltage. The equation used to find the total equivalent capacitance is Ceq = C1 + C2 + … + Cn.

In a series configuration, the current through each capacitor stays the same, but the voltage across each capacitor can be different. In this configuration, the sum of the potential differences is equal to the total voltage. The total capacitance is represented by 1/Ceq = 1/C1 + 1/C2 + … + 1/Cn.

In the present time, many types of capacitors are commercially available. These capacitors vary in capacitance from the picofarad range to more than a Farad, and their voltage range up to kilovolts. Generally, the higher the capacitance and voltage rating, the larger a capacitor is and the higher the cost of it. Most of the time, capacitors are classified according to the type of material used as the dielectric. The dielectrics used in capacitor are divided into two general categories: bulk insulators and electrolytic capacitors.

The main characteristic of capacitors using bulk insulators is that they do not have any polarity. Some examples of bulk dielectric capacitors are air-gap, ceramic, polystyrene, and polypropylene capacitors.

An air-gap capacitor is a capacitor that uses the surrounding air as a dielectric. These types of capacitors are mostly used in radio and radar equipment. The ceramic type of capacitors is constructed