Basic Principles of Capacitor’s and its types

Introduction

The Capacitor is a device that stores electrical energy in an electric field. It is a component that has the capacity to store energy in the form of an electrical charge producing a potential difference across its plates, excess like a Little battery-cell. some capacitors are used in power factor correction capacitors, but those all do the same thing. capacitor consists of two or more parallel conductive (metal) plates that are not connected separate other, but are electrically separated either by air or by any form of  like  as waxed paper, mica, ceramic, plastic or some kind of liquid gel as used in electrolytic capacitors. The insulating layer between a capacitors plates is ordinarily called the Dielectric.

• DC current cannot allow through the capacitor as it block. it is allowing instead a voltage to be present across the plates in the form of an electrical charge.
• It is different Type of Conductive Metal Plates of a capacitor can be either square, circular either rectangular, or they can be of a cylindrical either spherical shape with the general shape, size and construction of a parallel plate capacitor depending on that application and voltage rating.
• Direct current a capacitor charges up to its supply voltage but blocks the flow of current through it because the dielectric of a capacitor is non-conductive and essentially an insulator. However, when a capacitor is connected to an alternating current either AC circuit, the flow of the current appears to pass straight through the capacitor with little either no resistance.
• There are two types of electrical charge, positive charge are Protons and negative charge in the form of Electrons. When a DC voltage is placed athwart a capacitor, the positive (+V e) charge quickly accumulates on one plate as corresponding and opposite negative (-V e) charge accumulates on the other plate. For every particle of (+V e) charge that arrives at one plate a charge of the same sign will depart from the (-V e) plate.
• DC current cannot alow through the capacitor as it block. it is allowing instead a voltage to be present across the plates in the form of an electrical charge.
• It is different Type of Conductive Metal Plates of a capacitor can be either square, circular either rectangular, or they can be of a cylindrical either spherical shape with the general shape, size and construction of a parallel plate capacitor depending on that application and voltage rating.
• Direct current is a capacitor charges up to its supply voltage but blocks the flow of current through it because the dielectric of a capacitor is non-conductive and like an insulator.when a capacitor is connected to an alternating current , the flow of the current appears to pass straight through the capacitor with no resistance.
• There are two types of electrical charge, positive charge are Protons and negative charge in the form of Electrons. When a DC voltage is placed athwart a capacitor, the positive (+V e) charge quickly accumulates on one plate as corresponding and opposite negative (-V e) charge accumulates on the other plate. For every particle of (+V e) charge that arrives at one plate a charge of the same sign will depart from the (-V e) plate.

• The parallel plate capacitor is the simplest capacitor. It consist using two metal or metallised foil plates at a distance parallel to each other, with its capacitance value in Farads, being fixed with the surface area of the conductive plates and the distance of separation amid them. Altering any two of the values alters the value of that capacitance and this forms the basis of operation of the variable capacitors.
• capacitors store the energy of the electrons in the form of an electrical charge on the plates the larger the plates or smaller their separation the greater desire be the charge that the capacitor holds for any given voltage athwart its plates. In other words, larger plates, smaller distance, mightily capacitance.
• with applying a voltage to a capacitor and measuring the charge on the plates, the ratio of the charge Q to the voltage V will give the capacitance value of the capacitor and is so given as: C = Q/V this equation can also be re-arranged to give the familiar formula for the quantity of charge on the plates as: Q = C x V
• Although we have said that the charge is stored on the plates of a capacitor, it is more copious to say that the energy within the charge is stored in an “electrostatic field” between the two plates. When an electric current flows into the capacitor, it charges up, so the electrostatic field becomes much stronger as it stores mightily energy between the plates.
• Moreover, as the current flowing out of the capacitor, discharging it, the potential difference between the two plates decreases and the electrostatic field decreases as the energy moves out of the plates.
• The property of a capacitor to store charge on its plates in the form of an electrostatic field is termed the Capacitance of the capacitor. Not only that, but capacitance is also the property of a capacitor which resists the change of voltage athwart it.

The Capacitance of a Capacitor

• A capacitor has store an electrical charge on its two plates with the unit of capacitance being the Farad labelled after the British physicist Michael Faraday.
• capacitor has the capacitance of One Farad when a charge of One Coulomb is stored on the plates with a voltage of One volt. The Farad is a very large unit of measurement to use on its own so sub-multiples of the Farad are micro-farads, Nano-farads and Pico-farad, for an example.

Types of Capacitor

Dielectric Capacitor

Dielectric Capacitors are occasionally of the variable type were a continuous variation of capacitance is required for tuning transmitters, receivers and transistor radios. Variable dielectric capacitors are multi-plate air-spaced types that have a set of fixed plates (the stator vanes) and a set of movable plates. which move in between the fixed Plates.

Variable Capacitor Symbol

More over the continuously variable types, Pre-set type variable capacitors are also available called Trimmers. Film Capacitor Type

Film Capacitor Type

Film Capacitors those use polystyrene, polycarbonate or Teflon as their dielectrics are sometimes called “Plastic capacitors”. The construction of plastic film capacitors is Alike to that for paper film capacitors but use a plastic film instead of paper. The main advantage of plastic film capacitors compared to impregnated-paper types is that they operate well under conditions of high temperature, have smaller tolerances, high reliability. Examples of film capacitors are the rectangular metallised film and cylindrical film & foil types as shown below.

• Radial Lead Type

• Axial Lead Type

The film and foil types of capacitors are made from long thin strips of thin metal foil with the dielectric material sandwiched also which are wound into a tight roll and then sealed in paper or metal tubes.

• These film types require a much thicker dielectric film to reduce the risk of tears or punctures in the film, and is therefore more suited to lower capacitance values and larger case sizes. Metallised foil capacitors have the conductive film metallised sprayed directly onto each side of the dielectric which gives the capacitor self-healing properties and can therefore use much thinner dielectric films. This allows for higher capacitance values and petite case sizes for a given capacitance. Film and foil capacitors are commonly used for higher power and more precise applications.

Ceramic Capacitors

• Ceramic Capacitors or Disc Capacitors as they are generally called, are made by coating two sides of a small porcelain or ceramic disc with silver and are then stacked together to make a capacitor. For very low capacitance values a single ceramic disc of about 3-6mm is used. Ceramic capacitors have a high dielectric constant (High-K) and are available so that relatively high capacitance’s can be obtained in a small physical size.

• They exhibit large non-linear changes in capacitance against temperature and as a result are used as de-coupling or by-pass capacitors as they are also non-polarized devices. Ceramic capacitors have values ranging from a few Pico farads to one or two microfarads, ( μF ) but their voltage ratings are commonly quite low.

Electrolytic Capacitors

• Electrolytic Capacitors are commonly used when very large capacitance values are required. Here instead of using a very thin metallic film layer for one kind of electrodes, a semi-liquid electrolyte solution in the form of a jelly or paste is used which serves as the second electrode (usually the cathode).

• The dielectric is a very thin layer of oxide which is grown electro-chemically in production by the thickness of the film being less than ten microns. This insulating layer is so thin that it is possible to make capacitors with a large value of capacitance for a petite physical size as the distance between the plates, d is very small.
• The most of electrolytic types of capacitors are polarised, that is the DC voltage applied to the capacitor terminals must be of the correct polarity.