Capacitors & Categories

 

Capacitors & Categories

The capacitor is a passive device that stores electrical charges. A capacitor stores charges develop an electrical field between two conducting plates with a dielectric medium between them. The working mechanism includes the accumulation of positive charges on one plate. Since the dielectric medium between the plates doesn’t allow the charges to pass through until enough potential is developed, this causes the energy to develop, which is stored in the form of electrical charges called capacitance. Capacitors don’t ideally lose charge, but there is always some dissipation in real-life applications, which results in losing energy. By definition, the capacitance of a capacitor is defined as the ratio of charges to the voltage.

C = Q / V (Farad)

Units and Types:

Capacitors have a standard unit of farad and have various values of capacitance when manufactured. A farad is a very large capacitance unit, and the commonly used capacitance has very low capacitance. You may encounter capacitors from pico (10^-12) to micro (10^-6) farads.

Capacitors come in all size and capacity ranges; some common features considered in an application are:

SIZE: capacitors can range in various sizes and capacities. Their size is proportional to the capacitance, and a larger capacitance would require a larger size.

TOLERANCE: Every capacitance has a certain level of tolerance as capacitance can’t be made exactly as mentioned. There are silver, gold, and black marking on the capacitor, indicating a capacitor's tolerance.

VOLTAGE RATING: Every capacitor has a maximum rating for which it can store the charge. The rating is mentioned in figures or coded down in alphanumeric figures.

LEAKAGE CURRENT: Leakage current slowly drains away energy stored in the capacitor; no capacitor is prone to leakage current.

Categories of Capacitors:

     Ceramic Capacitors: The ceramic materials which contain dielectric ceramic material and are named after them are the most commonly produced and used capacitors. These have a small capacitance and are used in electronics; the advantage is that they are non-polarized and can be used in any configuration. They come in both surface mount and through-hole configuration.

     Aluminum And Tantalum: These are mid-range capacitance and are polarized and need s to be properly used in the circuit; otherwise end up blowing the circuit. The cathode is the negative plate, which is usually enclosed within an aluminum foil.

     Supercapacitors: These are high energy and high capacitance devices. However, they can’t compete against the batteries but are extremely useful in electronics where high energy is needed.

 

How To Use In Electrical Circuits:

Capacitors can be used in either series or parallel configuration. In a series configuration, one leg of the capacitor is connected to the capacitor's other leg to form a long chain-like structure. In the case of polarized, the capacitor's negative leg is connected to the positive end of the capacitor. However, in the parallel configuration, the terminals are connected face to face configuration i.e., the legs share common nodes. The total capacitance in the case of series decreases, whereas it increases in the case of parallel.

Difference Between AC And DC Capacitors:

AC capacitors have higher ratings as compared to DC capacitors. In the case of AC capacitor, polarity is an important factor and needs to be considered. However, non-polarized capacitors can be used in both AC and DC circuits. Also, when working with AC circuits at higher frequencies, the impedance is significantly reduced, as can be seen in the relation below:

X_c = 1/2  𝜋 F C

As the F increases the impedance of the capacitor decreases.