Capacitors Overview

What is a Capacitor?


A capacitor is an electrical component that holds a charge electrostatically. The devices are among the most common electrical components in use, though they didn't come into widespread use until the advent of radio in the early 1900s.

Capacitors come in a huge variety of sizes and shapes. They utilize a color-coding scheme similar to that used on resistors to differentiate them externally and are also sometimes marked with alphanumeric symbols to provide the same information to users.

History of Capacitors

While capacitors may have not come into widespread usage until the early 20th Century, they were discovered and experimented with by the late 1745. Early experimenters had a poor understanding of the electrical principles behind capacitance.

Ewald Georg von Kleist is generally credited with creating the first capacitor. He was experimenting with electricity when he found that he could store electrical charge in a glass jar filled with water. He produced the electricity that he stored in his primitive capacitor using a high-voltage electrostatic generator.

Von Kleist noticed that, when he touched the wires connected to the capacitors he got a much more significant shock than he did when touching the generator.

Another inventor, Pieter van Musschenbroek developed a capacitor very similar to Von Kleist's device. He also received a very powerful shock from the device.

An inventor named Daniel Gralath took several jars and combined them together so that he could increase the charge that the device would store.

Benjamin Franklin examined these devices, which were known as Leyden Jars, and figured out that the water was not actually holding the charge. He hypothesized that the glass was actually storing the charge. Franklin also coined the term battery to describe the devices, though batteries today are devices that use electrochemical cells to store a charge. Franklin actually took the term from a battery of cannons, which is a number of cannons used simultaneously to increase their overall power.

Capacitors didn't advance much in terms of design and technology until the early 1900s. When radio became available, the devices were adapted—shrunk and partially made of flexible components—to the new radio devices. Capacitors are still used to tune radios today.

The term condenser is sometimes used interchangeably with the term capacitor, though it is not all that common modern usage.

How Does a Capacitor Function?

A capacitor stores a charge electrostatically. This involved basic electric principles and, when used correctly, it lends these devices to a multitude of different uses.

In a simple capacitor, there are two conducting materials. The conducting materials are separated by an insulating material. Many capacitors use metal foil as the conductor and a very thin film of an insulating material to provide the insulation.

A capacitor functions when a potential difference exists across the conducting materials. This creates an electrostatic field in the insulator. Positive electrical charge collects on one of the conducting materials and a negative electrical charge collects on the others.

The capacitance of a capacitor is calculated by determining the ration between the charge in each conductor and the difference in potential between each of those charges.

Capacitance is measured in farads. Each farad is the equivalent of one coulomb per volt.

What Types of Applications Use Capacitors?

Capacitors are very common components and are used in an enormous variety of different applications.

Capacitors, as was mentioned, are used in radio tuning devices. They allow the radio too be precisely tuned to a given frequency and some of the early advances in capacitors came about so that higher radio frequencies could be accommodated.

Capacitors are also used to stabilize circuits. They are used in power line systems. They provide a stable voltage and flow of power across the lines, making them safer and more reliable.

Capacitors allow AC to flow but block DC. This allows them to be used in many different applications and, particularly, to smooth out current in analog devices.

What Types of Capacitors Exist?

There are many different types of capacitors available. Capacitors are often differentiated by the type of dielectric they have in them. For example, ceramic capacitors and aluminum capacitors are different types of capacitors that are differentiated in this regard.

Some types of capacitors have particular properties — such as low loss — that make them ideally suited for specific applications. In other cases, there may be multiple different types of capacitors that could be suitable for a given application, but the price of the capacitors available will dictate which capacitor is eventually chosen for the job. Some materials used in capacitors are rather exotic and, because of that, the cost of some capacitors can be very high.

There are also variable capacitors available. Variable capacitors utilize some sort of a control — usually a dial that is easily manipulated by the user — that allows the capacitance value of the component to be changed. To watch one of these in action, the user need only go to a radio in their car or in their home. Capacitors allow for the change in frequencies.

There are also new capacitors on the market that combine some of the features of batteries and the features of capacitors into one component. These have become extremely popular as solutions to some engineering and design problems, allowing a sort of best of both worlds scenario for designers.

Aluminum Capacitors

aluminium capacitorAluminum capacitors are used in applications when a compact design is advantageous. These capacitors are known to be lossy and are inappropriate for high-frequency applications. These are also capable of bursting if they are hooked up backwards and contain corrosive ingredients.

Array Capacitors

Array capacitors are used primarily for space-saving purposes. They allow significant compacting of designs compared to using discrete capacitors, in some cases.

Capacitor End Caps

Capacitor end caps are safety devices. They are attached to the ends of capacitors—typically smaller ones—and can prevent a disaster in the event that the capacitor is hooked up incorrectly. In such an instance, the electrolyte will boil and create tremendous pressure. The end cap will burst, allowing the pressure to escape without causing an explosion.

Capacitor Mounting Clips

Capacitor mounting clips are used to affix the capacitor to the circuit board on which it is installed or, in some cases, to another device. They simply provide stability and increase safety because of that.

Capacitor Sample Kits

Because builders sometimes need several different types of capacitors and sometimes their designs change, necessitating changes in components, sample kits are available. Capacitor sample kits are just kits that come with many different types of capacitors included in them.

Ceramic Multilayer Capacitors

ceramic capacitorCeramic multilayer capacitors are very common. They are seen in many different types of devices. They have a metal layer that provides the conducting surface and multiple layers of ceramic material that provide the insulating component. There are two different types of ceramic capacitors.

Class 1: These capacitors are notable for their high stability and low loss. They're utilized for resonant circuits, such as radios.

Class 2: These capacitors are utilized in bypass and coupling applications and have a high volumetric efficiency.

Ceramic Single Layer Capacitors

Ceramic single layer capacitors are ceramic capacitors, still using ceramic as insulating material, but that have a single layer of insulating material rather than multiple layers.

EDLC (Electric Double Layer Capacitor) Integration Kits

These are actually a new type of electrochemical capacitor. They are also known by the terms ultracapacitor and supercapacitor. EDLC (Electric Double Layer Capacitor) Integration Kits allow these devices to be integrated into circuits, allowing those circuits the benefits of these new types of capacitors.

Electric Double Layer Capacitors

Electric double layer capacitors are differentiated from other capacitors by having no solid dielectric component within them. These are a very new type of capacitor design that have some significant advantages that make them suitable for multiple applications. In some regards, these capacitors represent a coming together of the qualities of batteries and capacitors in one device.

Electrolytic Cap Nuts

Electrolytic cap nuts are not capacitors but, rather, are parts used on capacitors. These are installed onto the capacitor stud and used for mechanical fixing.

Mica Capacitors

Mica capacitors are capacitors that are utilized in applications where very high degrees of precision are required. They are commonly used in high-frequency applications, as well. They have qualities that allow them to provide a very low loss and a low capacitor change, making them suitable for applications when lossy capacitors would not be appropriate.

Multilayer Organic Capacitors

Multilayer organic capacitors are low loss capacitors that are often used in radio power amplifiers.

Niobium Capacitors

Niobium capacitors have similar properties to tantalum, but they come at a lower price. These are becoming more common on the market, as the price of their component materials has reduced in recent years.

Paper Capacitors

paper capacitorsPaper capacitors have been utilized for a very long time, but significant advances in manufacturing technologies have made them superior to older models. These capacitors use a metallized paper to carry power between the electrodes.

PEN Film Capacitors

PEN film capacitors utilize a dielectric made out of polyethylene naphthylate film. These can be made in very compact designs.

Polyester Film Capacitors

This is a type of film capacitor that uses polyester as its dielectric. Polyester film capacitors can be made in very small sizes.

Polyphenylene Sulphide Film Capacitors

Polyphenylene sulphide film capacitors utilize an insulator made out of a polymer material known as Torelina. These types of capacitors are only made in a metallized version.

Polypropylene Film Capacitors

Polypropylene film capacitors utilize a polypropylene film to provide the insulating element in the capacitor.

Polystyrene Film Capacitors

Styroflex Capacitors is a common name for these types of capacitors. These are used in a wide variety of different applications and have low leakage and low dissipation. Polystyrene film capacitors are not commonly available on the market today, but some manufacturers do still have them available.

RC Network Capacitors

These are a type of capacitor utilized on what is known as a resistor-capacitor circuit. RC network capacitors have one voltage or current source and, in their simplest incarnations, one capacitor and one resistor. These are commonly used as filter circuits, capable of removing certain frequencies from a signal but allowing others to pass.

Tantalum Capacitors

tantalum capacitorThese are types of electrolyte capacitors that utilize tantalum as their anode. They utilize an oxide as their insulator and those two layers are surrounded by a conductive cathode layer.Tantalum Capacitors have a very high capacitance relative to their size and weight. They also have a low leakage and are able to operate at higher temperature than other electrolytic capacitors. These capacitors are also notable for being very expensive and, for that reason, they are typically used in applications where their particular properties are imperative but may be substituted for in other applications.

Variable Trimmer Capacitors

Variable trimmer capacitors have the ability to change their capacitance, making them extremely important to some applications. The most notable use of this type of a capacitor is in a radio circuit, where it allows the individual to tune the radio to various frequencies. These capacitors have been improved upon significantly over time, originally having open plates but now being designed in more stable and safe designs.