What is Capacitor and How Does it Work?

What is a Capacitor?

A device used for storing electrical energy present in an electric field is termed a capacitor. It is a passive electronic component that has two terminals; its effect is known as capacitance. A capacitor is designed for adding capacitance to a circuit that exits between two electrical conductors in proximity present in a circuit.

A capacitor was originally known as a condenser or a condensator; these names are still used in many places other than in English. One exception being the capacitor microphones which is also known as a condenser microphone. The construction of practical capacitors and their physical form vary widely.

Generally, capacitors are known for having at least two electrical conductors that are present in the form of surfaces separated by a dielectric medium or metallic plates. This conductor may be a thin film, an electrolyte, sintered metal bead, or a foil.

The non-conducting dielectric works for increasing the charge capacity of the capacitor. Here, the materials commonly used are mica, plastic film, glass, air, oxide layers, and ceramic. These are used commonly used as parts of electrical circuits in various electrical devices. Capacitors do not dissipate energy, however, in real life, they do dissipate a small amount.

Common Types of Capacitors

There are many different types of capacitors are available for purchase. These types mainly depend on the plate structure, the type of internal dielectric, and the packaging of the device which strongly affect the characteristics and the applications of the capacitor.

The types of capacitors range from being very small which are used in radio circuits to big ones which are used for correcting high voltage and smoothing the circuit. There are various variable types of capacitors that allow the varying of capacitance value so that these may be used in radio or circuits requiring frequency tuning.

These types of capacitors are made by using metallic foil that is interlaced with thin sheets of Mylar or paraffin-impregnated in the form of dielectric material. Capacitors may look like tubes as metal foil plates are rolled for forming a small package into a cylinder. This small package is formed with the insulating dielectric material that is sandwiched in between.

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Capacitors that are small in size are normally constructed by using ceramic material which is then dipped in an epoxy resin for sealing. Capacitors play a significant role in electronic circuits, let’s read about the types of capacitors.

Dielectric Capacitors

This type of capacitor belongs to the variable type which offers a continuous variation of capacitance for the purpose of transmitter tuning, transistor radios, and receivers. Variable dielectric capacitors are the type of multi-plate air-spaced ones that have sets of movable plates and fixed plates.

Here, the moving plates are positioned with respect to the fixed plates that determine the overall capacitance value. When the two sets of plates have meshed together completely, the capacitance is said to be at its maximum. The tuning capacitors with high voltage have huge air gaps or spacings between the plates.

Trimmers                                                      

A pre-set variable type capacitor is available that is commonly known as a Trimmer. These are basically small devices that can be easily pre-set or adjusted to a specific capacitance value along with an aid of a tiny screwdriver.

Film Capacitor Type

This type of capacitor is the most common type which is available among the other types; it comprises various capacitors having different dielectric properties. These include polypropylene, metalized paper, polycarbonate, polystyrene, Teflon, polyester, etc.

These types of capacitors are present in different capacitance ranging from small to large on the basis of the actual type of capacitor and its voltage rating. These come in an assortment of case styles and shapes including metal hermetically sealed, epoxy case, and wrap and fill.

The film capacitors which use polycarbonate/Teflon or polystyrene as their dielectrics are commonly termed as “Plastic Capacitors”. This construction is the same as that of paper film capacitors, the difference is that here the plastic film is used instead of paper.

The major advantage or benefit of these capacitors, when compared to impregnated paper types is that these are capable of operating well under various conditions of reliability, service life, tolerances, and high temperature.

Axial Lead Type

The foil and film types of capacitors are created by using long thin strips made up of thin metal with a dielectric material that is sandwiched together. These are tied in a tight roll and then sealed with the help of metal tubes or paper.

These types of films need thick dielectric film for reducing the risk of tears or punctures that might arise. This is why these are more suited to larger case sizes and lower capacitance values. The metalized foil capacitors are known for possessing conductive film that is sprayed with metal on each dielectric side.

This is known for providing capacitors with self-healing properties which facilitates them to use thinner dielectric films. This further lead way to smaller case sizes and higher capacitance for the given capacitance. The foil and film capacitors are commonly used for the generation of high power and precise application.

Ceramic Capacitors

Ceramic capacitors are created by coating two sides of the ceramic disc or small porcelain with silver. These are further stacked together which leads to the creation of a capacitor. A single ceramic disc of 3-6mm is being used for the generation of very low capacitance.

These capacitors are also known as disc capacitors; these have a high dielectric constant and are present in order to provide high capacitance in a small physical size. This type of capacitor is known for exhibiting large non-linear changes in capacitance against temperature.

As a result, these are used as by-pass capacitors or de-coupling capacitors as these are also non-polarized devices. These capacitors have high values which range from some picofarads to one or two microfarads. Here, the voltage ratings provided are typically low.

Ceramic type capacitor is generally known for having a three-digit code that is printed on the body for identification of the capacitance value in pico-farads. Here the first two digits indicate the capacitor value while the third digit indicates the number of zeroes to be added.

Electrolytic Capacitors

This is a type of capacitor which is used when a huge capacitance value is needed. Instead of using a very thin metallic film layer, a semi-liquid electrolyte solution is used for one of the electrodes in paste or jelly form. This serves as the second electrode which is generally the cathode.

Dielectric is basically a thin layer of oxide that is grown electro-chemically along with the thickness of film which is less than ten microns. The thin insulating layer makes it possible to create capacitors having a large value of capacitance for a small physical size.

It has been observed that most of the electrolytic types of capacitors are polarised. This means that the DC voltage applied to the capacitor terminals must have the right polarity. The negative to the negative terminal and positive to the positive terminal with an incorrect polarisation may lead to a breakdown. This breakdown may either be of the insulating oxide layer or permanent damage.

Aluminium Electrolytic Capacitors

An aluminum electrolytic capacitor is of two types which include the etched foil type and the plain foil type. The capacitors receive very high capacitance values as per their size because of the thickness of the high breakdown voltage and aluminum oxide film.

The foil plates of the capacitor have been observed to be anodized with DC; this process sets the plate material polarity and finds out which side of the plate is positive and which side is negative.

Tantalum Electrolytic Capacitors

These capacitors and beads are available both in dry as well as wet electrolytic types with solid or dry tantalum being the most common types. Manganese dioxide is used as the second terminal by solid tantalum capacitors, these have been found to be smaller as compared to the equivalent aluminum capacitors physically.

The dielectric properties of tantalum oxide are better as compared to aluminum oxide as these have better capacitance stability and a low level of leakage currents. This makes this type of capacitors suitable to be used for by-passing, filtering, decoupling, blocking, and timing the applications.

Although tantalum capacitors are polarised, these are capable of tolerating connections made for reversing voltage in a much easier way as compared to the aluminum types. These are known for being rated at a much lower working voltage. The solid ones are generally used in circuits that have a smaller AC voltage as compared to the DC one.

There are some tantalum capacitor types that comprise two capacitors in one; these are connected negative-to-negative to form a capacitor that is non-polarised. These ones are created for their use in low voltage AC circuits as a non-polarised device.

Normally, a polarity mark helps in identifying the positive lead present on the capacitor’s body. The body of the tantalum bead capacitor here being in an oval geometrical shape.

How does Capacitor Work?

Capacitors are small in size just like a battery; they both work in a completely different manner but both store electrical energy. Let’s read about how capacitors work! There are terminals inside a capacitor that connects to two metal plates which are separated by a non-conducting substance or a dielectric.

A capacitor can be easily created by using a capacitor from two pieces of aluminum foil and a single piece of paper. It may not be a good capacitor when it comes to storage capacity, however, it does works.

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A dielectric may be described as a non-conductive substance theoretically. Practically, certain materials are used which are best suited so that the capacitor works well. Cellulose, Porcelain, Ceramic, Teflon, Mica, Mylar, and air are some of the best suited non-conductive materials used.

The kind of capacitor and what it is best suited for is dictated by the dielectric. While some capacitors are better for high-frequency uses, the others are best for high voltage applications depending on the type and size of the dielectric.

Capacitors are manufactured for serving various purposes; these may range from being the smallest plastic capacitor present in your calculator to an ultra-one used in a commuter bus.

POLARIZED VS NON-POLARIZED CAPACITORS

Capacitors are electronic devices that are known for storing energy via an electric field. These are widely used in electronics; what differentiate polarized and non-polarized capacitors from each other are their physical constraints. The important facts which affect their size include capacity and voltage. Generally, a larger size means that the capacitors are having a higher capacity.

Ceramic is the most widely used non-polarized capacitor, however, these are not used in high capacity. This is because their size increases and these are highly unstable. Polarized capacitors are known for providing better capacity with smaller sizes. Electrolytic type of capacitors is the most widely used polarized capacitor.

What differentiates these two is the difference in the process of their manufacturing for increasing the capacity. The non-polarized capacitor may be operated at a higher frequency as compared to the polarized capacitor. Further, non-polarized capacitors can be characterized as the ones that consume less power.

Common Uses of Capacitors

Capacitors are widely used for various purposes, one of the common uses include applying them in the conditioning of power supplies. These are known for allowing the AC signals to let the DC signals pass and block them when they are charged. Capacitors are known for swiftly splitting the two types of signals and cleaning the power supply.

One of the common uses of capacitors includes acting as a sensor for measuring various things comprising air humidity, mechanical strain, and fuel levels. Its capacitance depends on its structure; any changes in it may be measured as a gain or loss of capacitance. The material between the parallel plates and the distance are the two aspects of a capacitor that are used in sensing applications.

Capacitors are known for having found advanced applications in the information technology sector. DRAM or Dynamic Random Access Memory devices use these for representing the binary information as bits.

Applications of Capacitors

Now, let’s read about the applications of capacitors. Capacitors are put to use in various electronic circuits while their operation mode remains the same. The difference in capacitor forms may be utilized for providing and fulfilling various circuit functions. Different circuits need capacitors with specific values to possess attributes such as value accuracy, current capability, temperature stability, value range, and others.

There are capacitors that are available with different values, while some have large value ranges, the others are comparatively smaller. Yet others may have high current capabilities, stability and may be available with temperature coefficient having very low values.

Capacitors are often combined with resistors and used as the prime element of frequency-selective filters. The filter designs and topologies that are available here are numerous that may be tailored for performance and frequency by selecting the appropriate component quality and values. 

Advantages of Capacitors

The capacitors are capable of discharging in a fraction of a second, this is one of its major advantages. These are used for appliances that need a high level of speed such as in laser techniques and camera flash.

These are used for removing ripples by filling in the valleys and getting rid of peaks. It allows AC voltage to block and pass through the DC voltage. It is used in numerous electronic applications.

Capacitors are known for collecting, charging, and delivering energy quickly. The losses caused by these are small compared to the other storage mediums. They have a long service life and require very low maintenance.

Disadvantages of Capacitors

After going through the advantages of capacitors, let’s now know some of the disadvantages of capacitors. Capacitors have low energy capacity when compared to batteries. They have limited storage for energy per dollar cost and the stored energy is bound to deplete with time due to the internal occurrence of losses.