Various capacitors. The large cylinders are high value electrolytic types

A capacitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate. Practical capacitors are often classified according to the material used as the dielectric with the dielectrics divided into two broad categories: bulk insulators and metal-oxide films (so-called electrolytic capacitors). ... Image File history File linksMetadata Download high-resolution version (2592x1456, 520 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Farad Capacitor Metadata This file contains additional information, probably added from the digital camera or scanner used to... Image File history File linksMetadata Download high-resolution version (2592x1456, 520 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Farad Capacitor Metadata This file contains additional information, probably added from the digital camera or scanner used to... See Capacitor (component) for a discussion of specific types. ... The article on electrical energy is located elsewhere. ... Look up Electronic in Wiktionary, the free dictionary. ... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... In science and engineering, conductors, such as copper or aluminum, are materials with atoms having loosely held valence electrons. ... This box:      Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...

Capacitors are often used in electric and electronic circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals. This property makes them useful in electronic filters. An electrical network or electrical circuit is an interconnection of analog electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. ... Look up Electronic in Wiktionary, the free dictionary. ... Energy storage is the storing of some form of energy that can be drawn upon at a later time to perform some useful operation. ... For other uses, see Frequency (disambiguation). ... In the fields of communications, signal processing, and in electrical engineering more generally, a signal is any time-varying quantity. ... Wikipedia does not yet have an article with this exact name. ...

Capacitors are occasionally referred to as condensers. This is considered an antiquated term in English, but most other languages use an equivalent, like "condensateur" in French, "Kondensator" in German, "condensador" in Spanish, or "Kondensa" in Japanese.

History

Description and drawing of von Kleist's invention of the Leyden jar

In October 1745, Ewald Georg von Kleist of Pomerania in Germany invented the first recorded capacitor: a glass jar with water inside as one plate was held on the hand as the other plate. A wire in the mouth of the bottle received charge from an electric machine, and released it as a spark.^[1] Ewald Jürgen Georg von Kleist (June 1700 - December 10, 1748) was the dean of the cathedral at Kammin in Prussia and co-inventor of the Leyden jar. ... Pommern redirects here. ...

In the same year, Dutch physicist Pieter van Musschenbroek independently invented a very similar capacitor. It was named the Leyden jar, after the University of Leyden where van Musschenbroek worked. Daniel Gralath was the first to combine several jars in parallel into a "battery" to increase the charge storage capacity. Pieter (Petrus) van Musschenbroek (14 March 1692 - 19 September 1761) was a Dutch scientist who is credited with the invention of the Leyden jar, the first capacitor. ... Original capacitor The Leyden jar is a device for storing electric charge invented in 1745 by Pieter van Musschenbroek (1700–1748). ... Leiden University, located in the city of Leiden, is the oldest university in the Netherlands[1]. It is a member of the Coimbra Group, the Europaeum and the League of European Research Universities. ...

Benjamin Franklin investigated the Leyden jar, and proved that the charge was stored on the glass, not in the water as others had assumed. The earliest unit of capacitance was the 'jar', equivalent to about 1 nanofarad. This article is about the American political figure. ... Original capacitor The Leyden jar is a device for storing electric charge invented in 1745 by Pieter van Musschenbroek (1700–1748). ... Examples of various types of capacitors. ...

Early capacitors were also known as condensers, a term that is still occasionally used today. It was coined by Alessandro Volta in 1782 (derived from the Italian condensatore), with reference to the device's ability to store a higher density of electric charge than a normal isolated conductor. Most non-English European languages still use a word derived from "condensatore". For the concept car, see Toyota Alessandro Volta. ...

Theory of operation

Diagram of a parallel-plate capacitor

A capacitor consists of two conductive electrodes, or plates, separated by a dielectric, which prevents charge from moving directly between the plates. Charge may however be moved indirectly by external influences, such as a battery connecting the terminals. After removing the external influences, the charge on the plates persists. The separated charges attract each other, and an electric field is present between the plates. The simplest practical capacitor consists of two wide, flat, parallel plates separated by a thin dielectric layer. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... For other uses, see Electrode (disambiguation). ... A dielectric is a nonconducting substance, i. ... This box:      Coulombs torsion balance Coulombs law, developed in the 1780s by French physicist Charles Augustin de Coulomb, may be stated in scalar form as follows: The magnitude of the electrostatic force between two point electric charges is directly proportional to the product of the magnitudes of each... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ...

Assuming that the area of the plates A is much greater than their separation d, the instantaneous electric field between the plates E(t) is identical at any location away from the edges. If the instantaneous charge on a plate − q(t) is spread evenly,

,

where is the permittivity of the dielectric. The voltage v(t) between the plates is given by Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ...

,

where z is a position between the plates

Capacitance

Charge separation in a parallel-plate capacitor causes an internal electric field. A polarized dielectric spacer (orange) reduces the electric field and increase the capacitance.

A property called the capacitance C, which is a measure of the charge stored on each plate for a given voltage such that Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... This box:      Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...

q(t) = Cv(t),

where

for an ideal parallel plate capacitor.

In SI units, a capacitor has a capacitance of one farad when one coulomb of charge storage corresponds to one volt between its plates. Since the farad is a very large unit, capacitance is usually expressed in microfarads (µF), nanofarads (nF), or picofarads (pF). In general, capacitance is greater in devices with large plate areas, separated by small distances. When a dielectric is present between two charged plates, its molecules become polarized and reduce the internal electric field and hence the voltage. The capacitance is therefore strongly dependent on the quality of the dielectric. Look up si, Si, SI in Wiktionary, the free dictionary. ... Examples of various types of capacitors. ... The coulomb (symbol: C) is the SI unit of electric charge. ... Josephson junction array chip developed by NIST as a standard volt. ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ...

Energy storage

Work must be done by an external influence to move charge between the plates in a capacitor. When the external influence is removed, the charge separation persists and energy is stored in the electric field. If charge is later allowed to return to its equilibrium position, the energy is released. The work done in establishing the electric field, and hence the amount of energy stored, is given by In thermodynamics, work is the quantity of energy transferred from one system to another without an accompanying transfer of entropy. ...

.

The maximum energy that can be stored safely in a capacitor is limited by the breakdown voltage of the dielectric. Therefore, all capacitors made with a particular dielectric have approximately identical maximum energy density if the dielectric dominates their volume. Breakdown Voltage (Insulator) = The minimum voltage that makes an insulator react as a conductor. ... Energy density is the amount of energy stored in a given system or region of space per unit volume, or per unit mass, depending on the context. ...

Hydraulic analogy

Main article: Hydraulic analogy

As electrical circuitry can be modeled by fluid flow, a capacitor can be modeled as a chamber with a flexible diaphragm separating the input from the output. As can be determined intuitively as well as mathematically, this provides the correct characteristics: Since electric current is invisible and the processes at play in electronics are often difficult to understand in an intuitive way, it is common to teach electronics using analogies to more common sense objects and processes. ... This article or section should be merged with Fluid mechanics Fluid dynamics is the study of fluids (liquids and gases) in motion, and the effect of the fluid motion on fluid boundaries, such as solid containers or other fluids. ... An example of a diaphragm seal (in green) used to protect a pressure sensor. ...

• The pressure difference (voltage difference) across the unit is proportional to the integral of the flow (current).
• A steady state current cannot pass through it because the pressure will build up across the diaphragm until it equally opposes the source pressure,
• but a transient pulse or alternating current can be transmitted.
• An overpressure results in bursting of the diaphragm, analogous to dielectric breakdown.
• The capacitance of units connected in parallel is equivalent to the sum of their individual capacitances.

This article is about pressure in the physical sciences. ... HELLO EVERYONE!! Steady state is a more general situation than Dynamic equilibrium. ...

Aging

The capacitance of certain capacitors decreases as the component ages. In ceramic capacitors, this is caused by degradation of the dielectric. The type of dielectric and the ambient operating and storage temperatures are the most significant aging factors, while the operating voltage has a smaller effect. The aging process may be reversed by heating the component above the Curie point. Aging is fastest near the beginning of life of the component, and the device stabilizes over time.^[2] Electrolytic capacitors age as the electrolyte evaporates. In contrast with ceramic capacitors, this occurs towards the end of life of the component. The Curie point is a term in physics and materials science, named after Pierre Curie (1859-1906), and refers to a characteristic property of a ferromagnetic material. ... Electrolytic capacitors An electrolytic capacitor is a type of capacitor typically with a larger capacitance per unit volume than other types, making them valuable in relatively high-current and low-frequency electrical circuits. ...

Electric circuits

When a capacitor is connected to a current source, charge is transfered between its plates at a rate i(t) = dq(t) / dt. As the voltage between the plates is proportional to the charge, it follows that

.

Conversely, if a capacitor is connected to a voltage source, the resulting current is

DC sources

A simple resistor-capacitor circuit demonstrates charging of a capacitor.

A circuit containing only a resistor, a capacitor, a switch and a constant (DC) voltage source v_src(t) = V₀ in series is known as a charging circuit. From Kirchhoff's voltage law it follows that Resistor symbols (American) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... Kirchhoffs circuit laws are a pair of laws that deal with the conservation of charge and energy in electrical circuits, and were first described in 1845 by Gustav Kirchhoff. ...

,

where v_r(t) and v_c(t) are the voltages across the resistor and capacitor respectively. This reduces to a first order differential equation

Assuming that the capacitor is initially uncharged, there is no internal electric field, and the initial current is I₀ = V₀ / R. This initial condition allows solution of the differential equation as

.

The corresponding voltage drop across the capacitor is

.

Therefore, as charge increases on the capacitor plates, the voltage across the capacitor increases, until it reaches a steady-state value of V₀, and the current drops to zero. Both the current, and the difference between the source and capacitor voltage decay exponentially with respect to time. The time constant of the decay is given by τ = RC. In physics and engineering, the time constant usually denoted by the Greek letter , (tau), characterizes the frequency response of a first-order, linear time-invariant (LTI) system. ...

AC sources

When connected to an AC voltage source, the plates on a capacitor repeatedly charge and discharge relative to each other. The current varies sinusoidally, with a nonzero amplitude. For this reason, capacitors effectively conduct AC although charge ideally never passes directly through the dielectric. Since the current is proportional to the time derivative of the voltage, a sinusoidal current leads the voltage by a 90 degree phase shift, or equivalently a quarter cycle. The amplitude of the voltage depends on the amplitude of the current divided by the product of the frequency of the current with the capacitance, C. City lights viewed in a motion blurred exposure. ... A sine wave or sinusoid is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C is the vertical offset. ... For quantum-mechanical amplitude, see probability amplitude. ...

Impedance

The ratio of the phasor voltage across a circuit element to the phasor current through that element is called the impedance Z. For a capacitor, the impedance is given by See wikibooks book on Phasors A phasor is a constant complex number representing the complex amplitude (magnitude and phase) of a sinusoidal function of time. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ...

where is the capacitive reactance, is the angular frequency, f is the frequency), C is the capacitance in farads, and j is the imaginary unit. It has been suggested that Electric reactance be merged into this article or section. ... It has been suggested that this article or section be merged into Angular velocity. ... For other uses, see Frequency (disambiguation). ... In mathematics, the imaginary unit (or sometimes the Latin or the Greek iota, see below) allows the real number system to be extended to the complex number system . ...

While this relation (between the frequency domain voltage and current associated with a capacitor) is always true, the ratio of the time domain voltage and current amplitudes is equal to X_C only for sinusoidal (AC) circuits in steady state.

See derivation Deriving capacitor impedance. For an ideal capacitor, the capacitor current is proportional to the time rate of change of the voltage across the capacitor where the constant of proportionality is the capacitance, C: In the frequency domain, this equation becomes: The ratio of the voltage and current in the frequency domain is called...

Hence, capacitive reactance is the negative imaginary component of impedance. The negative sign indicates that the current leads the voltage by 90° for a sinusoidal signal, as opposed to the inductor, where the current lags the voltage by 90°.

The impedance is analogous to the resistance of a resistor. The impedance of a capacitor is inversely proportional to the frequency -- that is, for very high-frequency alternating currents the reactance approaches zero -- so that a capacitor is nearly a short circuit to a very high frequency AC source. Conversely, for very low frequency alternating currents, the reactance increases without bound so that a capacitor is nearly an open circuit to a very low frequency AC source. This frequency dependent behaviour accounts for most uses of the capacitor (see "Applications", below). Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Resistor symbols (American) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... This article is about proportionality, the mathematical relation. ... For alternate meanings see Short circuit (disambiguation) A short circuit (sometimes known as simply a short) is a fault whereby electricity moves through a circuit in an unintended path, usually due to a connection forming where none was expected. ...

Reactance is so called because the capacitor doesn't dissipate power, but merely stores energy. In electrical circuits, as in mechanics, there are two types of load, resistive and reactive. Resistive loads (analogous to an object sliding on a rough surface) dissipate the energy delivered by the circuit as heat, while reactive loads (analogous to a spring or frictionless moving object) store this energy, ultimately delivering the energy back to the circuit.

Also significant is that the impedance is inversely proportional to the capacitance, unlike resistors and inductors for which impedances are linearly proportional to resistance and inductance respectively. This is why the series and shunt impedance formulae (given below) are the inverse of the resistive case. In series, impedances sum. In parallel, conductances sum.

Laplace equivalent (s-domain)

When using the Laplace transform in circuit analysis, the capacitive impedance is represented in the s domain by: In the branch of mathematics called functional analysis, the Laplace transform, , is a linear operator on a function f(t) (original) with a real argument t (t ≥ 0) that transforms it to a function F(s) (image) with a complex argument s. ...

where C is the capacitance, and s (= σ+jω) is the complex frequency.

Displacement current

The physicist James Clerk Maxwell invented the concept of displacement current, dD/dt, to make Ampère's law consistent with conservation of charge in cases where charge is accumulating as in a capacitor. He interpreted this as a real motion of charges, even in vacuum, where he supposed that it corresponded to motion of dipole charges in the aether. Although this interpretation has been abandoned, Maxwell's correction to Ampère's law remains valid. James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist. ... Displacement current is a quantity related to changing electric field. ... An electric current produces a magnetic field. ... The Earths magnetic field, which is approximately a dipole. ... The luminiferous aether: it was hypothesised that the Earth moves through a medium of aether that carries light In the late 19th century luminiferous aether (light-bearing aether) was the term used to describe a medium for the propagation of light. ...

Networks

Series or parallel arrangements

Main article: Series and parallel circuits

Capacitors in a parallel configuration each have the same potential difference (voltage). Their total capacitance (C_eq) is given by: Electrical circuit components can be connected together in one of two ways: series or parallel. ... Electrical circuit components can be connected together in one of two ways: series or parallel. ...

The reason for putting capacitors in parallel is to increase the total amount of charge stored. In other words, increasing the capacitance also increases the amount of energy that can be stored. Its expression is: Image File history File links This is a lossless scalable vector image. ...

The current through capacitors in series stays the same, but the voltage across each capacitor can be different. The sum of the potential differences (voltage) is equal to the total voltage. Their total capacitance is given by: Electrical circuit components can be connected together in one of two ways: series or parallel. ...

In parallel the effective area of the combined capacitor has increased, increasing the overall capacitance. While in series, the distance between the plates has effectively been increased, reducing the overall capacitance. Image File history File links This is a lossless scalable vector image. ...

In practice capacitors will be placed in series as a means of economically obtaining very high voltage capacitors, for example for smoothing ripples in a high voltage power supply. Three "600 volt maximum" capacitors in series, will increase their overall working voltage to 1800 volts. This is of course offset by the capacitance obtained being only one third of the value of the capacitors used. This can be countered by connecting 3 of these series set-ups in parallel, resulting in a 3x3 matrix of capacitors with the same overall capacitance as an individual capacitor but operable under three times the voltage. In this application, a large resistor would be connected across each capacitor to ensure that the total voltage is divided equally across each capacitor and also to discharge the capacitors for safety when the equipment is not in use. Resistor symbols (American) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ...

Another application is for use of polarized capacitors in alternating current circuits; the capacitors are connected in series, in reverse polarity, so that at any given time one of the capacitors is not conducting...

Capacitor/inductor duality

In mathematical terms, the ideal capacitor can be considered as an inverse of the ideal inductor, because the voltage-current equations of the two devices can be transformed into one another by exchanging the voltage and current terms. Just as two or more inductors can be magnetically coupled to make a transformer, two or more charged conductors can be electrostatically coupled to make a capacitor. The mutual capacitance of two conductors is defined as the current that flows in one when the voltage across the other changes by unit voltage in unit time. An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... For other uses, see Transformer (disambiguation). ...

Capacitor types

Main article: capacitor (component)

Practical capacitors are available commercially in many different forms. The type of internal dielectric, the structure of the plates and the device packaging all strongly affect the characteristics of the capacitor, and its applications. Practical capacitors are often classified according to the material used as the dielectric with the dielectrics divided into two broad categories: bulk insulators and metal-oxide films (so-called electrolytic capacitors). ...

A 12 pF 20 kV fixed vacuum capacitor

Image File history File links Metadata Size of this preview: 796 × 599 pixelsFull resolution‎ (1,360 × 1,024 pixels, file size: 626 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Metadata Size of this preview: 796 × 599 pixelsFull resolution‎ (1,360 × 1,024 pixels, file size: 626 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ...

Dielectric materials

Most types of capacitor include a dielectric spacer, which increases their capacitance. However, low capacitance devices are available with a vacuum between their plates, which allows extremely high voltage operation and low losses. Air filled variable capacitors are also commonly used in radio tuning circuits. Look up Vacuum in Wiktionary, the free dictionary. ...

Several solid dielectrics are available, including paper, plastic, glass, mica and ceramic materials. Paper was used extensively in older devices and offers relatively high voltage performance. However, it is susceptible to water absorption, and has been largely replaced by plastic film capacitors. Plastics offer better stability, and aging performance, which makes them useful in timer circuits although they may be limited to low operating temperatures and frequencies. Ceramic capacitors are generally small, cheap and useful for high frequency applications, although their capacitance varies strongly with voltage, and they age poorly. They are broadly categorized as Class 1 dielectrics, which have predictable variation of capacitance with temperature or Class 2 dielectrics, which can operate at higher voltage. Glass and mica capacitors are extremely reliable, stable and tolerant to high temperatures and voltages, but are too expensive for most mainstream applications. The EIA Class 1 dielectric materials are ceramic dielectric materials used in ceramic capacitors of small values (typically <5 nF). ... The EIA Class 2 dielectric materials are ceramic dielectric materials used in ceramic capacitors. ...

Capacitor materials. From left: multilayer ceramic, ceramic disc, multilayer polyester film, tubular ceramic, polystyrene, metalized polyester film, aluminum electrolytic. Major scale divisions are cm.

Electrolytic capacitors use an aluminum or tantalum plate with an oxide dielectric layer. The second electrode is a liquid electrolyte. Electrolytic capacitors offer very high capacitance but suffer from poor tolerances, high instability, gradual loss of capacitance especially when subjected to heat, and high leakage current. The conductivity of the electrolyte drops at low temperatures, which increases equivalent series resistance. While widely used for power-supply conditioning, poor high-frequency characteristics make them unsuitable for many applications. Tantalum capacitors offer better frequency and temperature characteristics than aluminum, but higher dielectric absorption and leakage.^[3]. OS-CON (or OC-CON) capacitors are a polymerized organic semiconductor solid-electrolyte type that offer longer life at higher cost than standard electrolytic capacitors. Image File history File links Capacitors/Condensators from German wiki http://de. ... Image File history File links Capacitors/Condensators from German wiki http://de. ... An electrolyte is any substance containing free ions that behaves as an electrically conductive medium. ... see Equivalent series inductance for a related discussion Equivalent series resistance (ESR) is an effective resistance that is used to describe the resistive parts of the impedance of certain electrical components. ... OSCON or OS-CON capacitors are a polymerized organic semiconductor solid-electrolyte device. ...

Several other types of capacitor are available for specialist applications. Supercapacitors made from carbon aerogel, carbon nanotubes, or highly porous electrode materials offer extremely high capacity and can be used in some applications instead of rechargeable batteries. AC capacitors are specifically designed to work on line (mains) voltage AC power circuits. They are commonly used in electric motor circuits and are often designed to handle large currents, so they tend to be physically large. They are usually ruggedly packaged, often in metal cases that can be easily grounded/earthed. They also tend to have rather high DC breakdown voltages. MC and BC series supercapacitors (up to 3000 farad capacitance) produced by Maxwell Technologies Supercapacitors, also known as ultracapacitors or electrochemical double layer capacitors (EDLC), are electrochemical capacitors that have an unusually high energy density when compared to common capacitors, typically on the order of thousands of times greater than... A 2. ... A rechargeable lithium polymer Nokia mobile phone battery. ... For other kinds of motors, see motor. ...

Capacitor packages: SMD ceramic at top left; SMD tantalum at bottom left; through-hole tantalum at top right; through-hole electrolytic at bottom right. Major scale divisions are cm.

Image File history File links Download high resolution version (1013x974, 136 KB) Summary Description: SMD capacitors Author, date of creation: selfmade by Shaddack, 6 November 2005 Source: self-made Copyright: Public Domain (PD) Comments: SMD capacitors ceramic and electrolytic (the black plastic ones), with classic types for comparison Licensing File... Image File history File links Download high resolution version (1013x974, 136 KB) Summary Description: SMD capacitors Author, date of creation: selfmade by Shaddack, 6 November 2005 Source: self-made Copyright: Public Domain (PD) Comments: SMD capacitors ceramic and electrolytic (the black plastic ones), with classic types for comparison Licensing File... Surface-mount components on a flash drives circuit board Surface mount technology (SMT) is a method for constructing electronic circuits in which the components (SMC, or Surface Mounted Components) are mounted directly onto the surface of printed circuit boards (PCBs). ... Through-hole technology, also spelled thru-hole, refers to the mounting scheme used for electronic components that involves the use of pins on the components that are inserted into holes drilled in printed boards and soldered to pads on the opposite side. ...

Structure

Capacitors may have their plates arranged in many configurations, for example axially or radially. Small, cheap discoidal ceramic capacitors have existed since the 1930s, and remain in widespread use. Since the 1980s, surface mount packages for capacitors have been widely used. These packages are extremely small and lack connecting leads, allowing them to be soldered directly onto the surface of printed circuit boards. Surface mount components avoid undesirable high-frequency effects due to the leads and simplify automated assembly, although manual handling is made difficult due to their small size. Surface-mount components on a keydrives circuit board Surface mount technology (SMT) is a method for constructing electronic circuits in which the components are mounted directly onto the surface of printed circuit boards (PCBs). ... Close-up photo of one side of a motherboard PCB, showing conductive traces, vias and solder points for through-hole components on the opposite side. ...

Variable capacitors are available in various forms. Mechanically controlled variable capacitors allow the plate spacing to be adjusted, for example by rotating or sliding a set of movable plates into alignment with a set of stationary plates. Very cheap variable capacitors squeeze together alternating layers of aluminum and plastic with a screw, but the resulting capacitance is unstable, and unreproducible. Electrical control of capacitance is achievable with varactors (or varicaps), which are reverse-biased semiconductor diodes whose depletion region width varies with applied voltage. They are used in phase-locked loops, amongst other applications. A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. ... Trimmer potentiometers or trimpots. A trimmer is a miniature adjustable electrical component. ... A varicap diode, varactor diode or tuning diode is a type of diode used in electronic circuits. ... Reverse-biased usually refers to how a diode is used in a circuit. ... Types of diodes. ... In semiconductor physics, the depletion region, also called depletion layer or depletion zone, as well as the junction region or the space charge region is an insulating region within a conductive, doped semiconductor material where the charge carriers have diffused away or have been swept away by an electric field. ... Many electronic systems use internal clocks which are required to be phase-aligned to and/or frequency multiples of some external reference clock. ...

Applications

Capacitor symbols

Capacitor	Polarized capacitors	Variable capacitor

Capacitors have various uses in electronic and electrical systems. Image File history File links Capacitor_Symbol_alternative. ... Image File history File links Polarized_capacitor_symbol_alternative. ... Image File history File links Polarized_capacitor_symbol_2. ... Image File history File links Polarized_capacitor_symbol_3. ... Image File history File links Polarized_capacitor_symbol_4. ... Image File history File links Polarized_capacitor_symbol_5. ... Image File history File links Variable_capacitor_symbol_2. ...

Energy storage

A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery. Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed. (This prevents loss of information in volatile memory.) For other uses, see Battery. ...

Power conditioning

Reservoir capacitors are used in power supplies where they smooth the output of a full or half wave rectifier. They can also be used in charge pump circuits as the energy storage element in the generation of higher voltages than the input voltage. The pulsating DC from an AC rectifier(either half wave or full wave) needs to be smoothened to be useful. ... A wall wart style variable DC power supply with its cover removed. ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ... A charge pump is an electronic circuit that uses capacitors as energy storage elements to create either a higher or lower voltage power source. ...

Capacitors are connected in parallel with the power circuits of most electronic devices and larger systems (such as factories) to shunt away and conceal current fluctuations from the primary power source to provide a "clean" power supply for signal or control circuits. Audio equipment, for example, uses several capacitors in this way, to shunt away power line hum before it gets into the signal circuitry. The capacitors act as a local reserve for the DC power source, and bypass AC currents from the power supply. This is used in car audio applications, when a stiffening capacitor compensates for the inductance and resistance of the leads to the lead-acid car battery. It has been suggested that In car entertainment be merged into this article or section. ... Lead-acid batteries are the most commonly used rechargeable batteries today. ... Lead-acid car battery A car battery is a type of rechargeable battery that supplies electric energy to an automobile[1]. Usually this refers to a SLI battery (Starting - Lighting - Ignition) to power the starter motor, the lights and the ignition system of a vehicle’s engine. ...

Power factor correction

Capacitors are used in power factor correction. Such capacitors often come as three capacitors connected as a three phase load. Usually, the values of these capacitors are given not in farads but rather as a reactive power in volt-amperes reactive (VAr). The purpose is to counteract inductive loading from electric motors and fluorescent lighting in order to make the load appear to be mostly resistive. Power factor correction (PFC) is a technique of counteracting the undesirable effects of electric loads that create a power factor (p. ... In electrical engineering, three-phase electric power systems have at least three conductors carrying voltage waveforms that are 2π/3 radians (120°,1/3 of a cycle) offset in time. ... If an electric circuit has a well-defined output terminal, the circuit connected to this terminal (or its input impedance) is the load. ... Reactive power is an abstract quantity, typically used by power engineers to describe a certain type of energy flow in an electric distribution system. ... Induction Motor (IM) is one kind of AC motor where power is supplied to the rotating device by induction. ... A compact fluorescent lamp A fluorescent lamp is a type of electric lamp that excites argon and mercury vapor to create luminescence. ...

Filtering

Signal coupling

Main article: capacitive coupling

Because capacitors pass AC but block DC signals (when charged up to the applied dc voltage), they are often used to separate the AC and DC components of a signal. This method is known as AC coupling or "capacitive coupling". Here, a large value of capacitance, whose value need not be accurately controlled, but whose reactance is small at the signal frequency, is employed. In electronics, capacitive coupling is the transfer of energy from one circuit to another by means of the mutual capacitance between the circuits. ... In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... It has been suggested that Electric reactance be merged into this article or section. ...

Decoupling

Main article: decoupling capacitor

A decoupling capacitor is a capacitor used to decouple one part of a circuit from another. Noise caused by other circuit elements is shunted through the capacitor reducing the effect they have on the rest of the circuit. It is most commonly used between the power supply and ground. A decoupling capacitor is a capacitor used to decouple one part of an electrical network (circuit) from another. ...

An alternative name is bypass capacitor as it is used to bypass the power supply or other high impedance component of a circuit.

Noise filters, motor starters, and snubbers

When an inductive circuit is opened, the current through the inductance collapses quickly, creating a large voltage across the open circuit of the switch or relay. If the inductance is large enough, the energy will generate a spark, causing the contact points to oxidize, deteriorate, or sometimes weld together, or destroying a solid-state switch. A snubber capacitor across the newly opened circuit creates a path for this impulse to bypass the contact points, thereby preserving their life; these were commonly found in contact breaker ignition systems, for instance. Similarly, in smaller scale circuits, the spark may not be enough to damage the switch but will still radiate undesirable radio frequency interference (RFI), which a filter capacitor absorbs. Snubber capacitors are usually employed with a low-value resistor in series, to dissipate energy and minimize RFI. Such resistor-capacitor combinations are available in a single package. A snubber is a simple electrical circuit used to suppress (snub) electrical transients. ... Breaker arm with contact points at the left. ... The ignition system of an internal-combustion engine is an important part of the overall engine system that provides for the timely burning of the fuel mixture within the engine. ... A typical spark transmitter circuit. ... Radio Frequency Interference (RFI) is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. ...

In an inverse fashion, to initiate current quickly through an inductive circuit requires a greater voltage than required to maintain it; in uses such as large motors, this can cause undesirable startup characteristics, and a motor starting capacitor is used to increase the coil current to help start the motor.

Capacitors are also used in parallel to interrupt units of a high-voltage circuit breaker in order to equally distribute the voltage between these units. In this case they are called grading capacitors. For other uses, see Circuit breaker (disambiguation). ...

In schematic diagrams, a capacitor used primarily for DC charge storage is often drawn vertically in circuit diagrams with the lower, more negative, plate drawn as an arc. The straight plate indicates the positive terminal of the device, if it is polarized (see electrolytic capacitor). Electrolytic capacitors An electrolytic capacitor is a type of capacitor typically with a larger capacitance per unit volume than other types, making them valuable in relatively high-current and low-frequency electrical circuits. ...

Signal processing

The energy stored in a capacitor can be used to represent information, either in binary form, as in DRAMs, or in analogue form, as in analog sampled filters and CCDs. Capacitors can be used in analog circuits as components of integrators or more complex filters and in negative feedback loop stabilization. Signal processing circuits also use capacitors to integrate a current signal. The ASCII codes for the word Wikipedia represented in binary, the numeral system most commonly used for encoding computer information. ... Dram can mean several things: Dram (unit), an imperial unit of volume Dram, an imperial unit of weight or mass, see avoirdupois and apothecaries system Ottoman dram, a unit of weight, see dirhem Armenian dram, a monetary unit DRAM, a type of RAM Category: ... An analog sampled filter an electronic filter that is a hybrid between an analog and a digital filter. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... It has been suggested that this article or section be merged with Analog electronics. ... This article does not cite any references or sources. ... This article is about the concept of integrals in calculus. ...

Tuned circuits

Capacitors and inductors are applied together in tuned circuits to select information in particular frequency bands. For example, radio receivers rely on variable capacitors to tune the station frequency. Speakers use passive analog crossovers, and analog equalizers use capacitors to select different audio bands. An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... An RLC circuit (also known as a resonant circuit or a tuned circuit) is an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C), connected in series or in parallel. ... Audio crossovers are a class of electronic filters designed specifically for use in audio applications, especially hi-fi. ...

In a tuned circuit such as a radio receiver, the frequency selected is a function of the inductance (L) and the capacitance (C) in series, and is given by: An RLC circuit (sometimes known as resonant or tuned circuit) is an electrical circuit comprising a resistor (R), an inductor (L), and a capacitor (C), connected in series or in parallel. ... For the device which is a tuner (radio) and a amplifier and/or loudspeaker, see receiver (home stereo). ... For other uses, see Frequency (disambiguation). ...

This is the frequency at which resonance occurs in an LC circuit. This article is about resonance in physics. ... An LC circuit consists of an inductor, represented by the letter L, and a capacitor, represented by the letter C. When connected together, an electrical current can alternate between them at an angular frequency of where L is the inductance in henries, and C is the capacitance in farads. ...

Other applications

Sensing

Most capacitors are designed to maintain a fixed physical structure. However, various factors can change the structure of the capacitor; the resulting change in capacitance can be used to sense those factors. Not to be confused with censure, censer, or censor. ...

Changing the dielectric: the effects of varying the physical and/or electrical characteristics of the dielectric can also be of use. Capacitors with an exposed and porous dielectric can be used to measure humidity in air.

Changing the distance between the plates: Capacitors are used to accurately measure the fuel level in airplanes. Capacitors with a flexible plate can be used to measure strain or pressure. Capacitors are used as the sensor in condenser microphones, where one plate is moved by air pressure, relative to the fixed position of the other plate. Some accelerometers use MEMS capacitors etched on a chip to measure the magnitude and direction of the acceleration vector. They are used to detect changes in acceleration, eg. as tilt sensors or to detect free fall, as sensors triggering airbag deployment, and in many other applications. Some fingerprint sensors use capacitors. Additionally, a user can adjust the pitch of a theremin musical instrument by moving his hand since this changes the effective capacitance between the user's hand and the antenna. Airplane and Aeroplane redirect here. ... Not to be confused with censure, censer, or censor. ... A microphone with a cord A microphone, sometimes called a mic (pronounced mike), is a device that converts sound into an electrical signal. ... A depiction of an accelerometer designed at Sandia National Laboratories. ... A mite next to a gear set produced using MEMS. Courtesy Sandia National Laboratories, SUMMiTTM Technologies, www. ... For the Mozilla crash reporting software previously called Airbag, see Breakpad. ... This article is about fingerprint authentication. ... Léon Theremin playing an early theremin The theremin (originally pronounced but often anglicized as [1]), or thereminvox, is one of the earliest fully electronic musical instruments. ...

Changing the effective area of the plates: capacitive touch switches [2] [3] [4].

Pulsed power and weapons

Groups of large, specially constructed, low-inductance high-voltage capacitors (capacitor banks) are used to supply huge pulses of current for many pulsed power applications. These include electromagnetic forming, Marx generators, pulsed lasers (especially TEA lasers), pulse forming networks, radar, fusion research, and particle accelerators. An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Φ through the circuit. ... Pulsed power is the term used to describe the science and technology of accumulating energy over a relatively long period of time and releasing it very quickly thus increasing the instantaneous power. ... A pinched aluminium can, produced from a pulsed magnetic field created by rapidly discharging 2 kilojoules from a high voltage capacitor bank into a 3-turn coil of heavy gauge wire. ... A Marx generator is a type of electrical circuit first described by Erwin Marx in 1924 whose purpose is to generate a high-voltage pulse. ... For other uses, see Laser (disambiguation). ... // Overview A TEA Laser is one of the most easily (at least compared with other models) and inexpensive way to generate laser light. ... A Pulse forming network (PFN) converts direct current or alternating current to continous directional square pulses at high energy levels of high frequency. ... For other uses, see Radar (disambiguation). ... Zork universe Zork games Zork Anthology Zork trilogy Zork I   Zork II   Zork III Beyond Zork   Zork Zero   Planetfall Enchanter trilogy Enchanter   Sorcerer   Spellbreaker Other games Wishbringer   Return to Zork Zork: Nemesis   Zork Grand Inquisitor Zork: The Undiscovered Underground Topics in Zork Encyclopedia Frobozzica Characters   Kings   Creatures Timeline   Magic   Calendar... Atom Smasher redirects here. ...

Large capacitor banks(Reservoir) are used as energy sources for the exploding-bridgewire detonators or slapper detonators in nuclear weapons and other specialty weapons. Experimental work is under way using banks of capacitors as power sources for electromagnetic armour and electromagnetic railguns or coilguns. The exploding-bridgewire detonator (EBW, also known as exploding wire detonator) was invented by Luis Alvarez and Lawrence Johnston for the Fat Man-type bombs of the Manhattan Project, during their work in Los Alamos National Laboratory. ... A slapper detonator is a relatively recent kind of a detonator developed in Lawrence Livermore National Laboratory. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets or shells, protecting the soldiers inside from enemy fire. ... For railroad artillery, see railway gun. ... Not to be confused with Gaussian gun. ...

See also Explosively pumped flux compression generator. A cutaway view of a flux compression generator. ...

Hazards and safety

Capacitors may retain a charge long after power is removed from a circuit; this charge can cause shocks (sometimes fatal) or damage to connected equipment. For example, even a seemingly innocuous device such as a disposable camera flash unit powered by a 1.5 volt AA battery contains a capacitor which may be charged to over 300 volts. This is easily capable of delivering an extremely painful shock. ‹ The template below (Expand) is being considered for deletion. ...

Care must be taken to ensure that any large or high-voltage capacitor is properly discharged before servicing the containing equipment. For board-level capacitors, this is done by placing a bleeder resistor across the terminals, whose resistance is large enough that the leakage current will not affect the circuit, but small enough to discharge the capacitor shortly after power is removed. High-voltage capacitors should be stored with the terminals shorted, since temporarily discharged capacitors can develop potentially dangerous voltages when the terminals are left open-circuited. A bleeder resistor is a resistor placed in parallel of a high-voltage supply for the purposes of discharging the energy stored in the power sources filter capacitors or other components that store electrical energy. ... For alternate meanings see Short circuit (disambiguation) A short circuit (sometimes known as simply a short) is a fault whereby electricity moves through a circuit in an unintended path, usually due to a connection forming where none was expected. ...

Large oil-filled old capacitors must be disposed of properly as some contain polychlorinated biphenyls (PCBs). It is known that waste PCBs can leak into groundwater under landfills. If consumed by drinking contaminated water, PCBs are carcinogenic, even in very tiny amounts. If the capacitor is physically large it is more likely to be dangerous and may require precautions in addition to those described above. New electrical components are no longer produced with PCBs. ("PCB" in electronics usually means printed circuit board, but the above usage is an exception.) Capacitors containing PCB were labelled as containing "Askarel" and several other trade names. Labelling transformers containing PCBs. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. ... Look up Dump in Wiktionary, the free dictionary. ... Look up carcinogen in Wiktionary, the free dictionary. ... Part of a 1983 Sinclair ZX Spectrum computer board. ...

High-voltage

Above and beyond usual hazards associated with working with high voltage, high energy circuits, there are a number of dangers that are specific to high voltage capacitors. High voltage capacitors may catastrophically fail when subjected to voltages or currents beyond their rating, or as they reach their normal end of life. Dielectric or metal interconnection failures may create arcing called an arc fault, within oil-filled units that vaporizes dielectric fluid, resulting in case bulging, rupture, or even an explosion that disperses flammable oil, starts fires, and damages nearby equipment, called flash - melt down, Rigid cased cylindrical glass or plastic cases are more prone to explosive rupture than rectangular cases due to an inability to easily expand under pressure. Capacitors used in RF or sustained high current applications can overheat, especially in the center of the capacitor rolls. The trapped heat may cause rapid interior heating and destruction, even though the outer case remains relatively cool. Capacitors used within high energy capacitor banks can violently explode when a fault in one capacitor causes sudden dumping of energy stored in the rest of the bank into the failing unit. And, high voltage vacuum capacitors can generate soft X-rays even during normal operation. Proper containment, fusing, and preventative maintenance can help to minimize these hazards.

High voltage capacitors can benefit from a pre-charge to limit in-rush currents at power-up of HVDC circuits. This will extend the life of the component and may mitigate high voltage hazards. HVDC (high voltage direct current) electric power systems must be activated before power can be distributed. ...

See also

Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... Leaking Chhsi capacitors on a MSI 694D Pro motherboard. ... A motherboard is the central or primary circuit board making up a complex electronic system, such as a modern computer. ... The process of circuit design can cover systems ranging from national power grids all the way down to the individual transistors within an integrated circuit. ... A decoupling capacitor is a capacitor used to decouple one part of an electrical network (circuit) from another. ... Various components An electronic component is a basic electronic element usually packaged in a discrete form with two or more connecting leads or metallic pads. ... In physics, the electric displacement field or electric flux density or electric induction is a vector field that appears in Maxwells equations. ... Surface mount electronic components Electronics is the study of the flow of charge through various materials and devices such as semiconductors, resistors, inductors, capacitors, nano-structures and vacuum tubes. ... Cross coupled LC oscillator with output on top An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. ... Rectifiers convert an AC supply into a pulsating DC. Most modern electronic devices require a steady DC supply. ... A light emitting capacitor, or LEC, works in largely the same way as conventional capacitors, except that the dielectric between the outside contacts is a chemical that gives off photons when the capacitor is charged. ... The pulsating DC from an AC rectifier(either half wave or full wave) needs to be smoothened to be useful. ... MC and BC series supercapacitors (up to 3000 farad capacitance) produced by Maxwell Technologies Supercapacitors, also known as ultracapacitors or electrochemical double layer capacitors (EDLC), are electrochemical capacitors that have an unusually high energy density when compared to common capacitors, typically on the order of thousands of times greater than... // A Vacuum Variable Capacitor 20-1000pF at 10Kv. ... A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. ... A capacitance meter is a piece of electronic test equipment used to measure capacitors. ...

Notes

References

• Zorpette, Glen (2005). "Super Charged: A Tiny South Korean Company is Out to Make Capacitors Powerful enough to Propel the Next Generation of Hybrid-Electric Cars". IEEE Spectrum 42 (1). ISSN 0018-9235. 
• (1991) The ARRL Handbook for Radio Amateurs, 68th ed, Newington CT USA: The Amateur Radio Relay League. 
• Huelsman, Lawrence P. (1972). Basic Circuit Theory with Digital Computations, Series in computer applications in electrical engineering. Englewood Cliffs: Prentice-Hall. ISBN 0-13-057430-9. 
• Philosophical Transactions of the Royal Society LXXII, Appendix 8, 1782 (Volta coins the word condenser)
• A. K. Maini "Electronic Projects for Beginners", "Pustak Mahal", 2nd Edition: March, 1998 (INDIA)
• Spark Museum (von Kleist and Musschenbroek)
• Biography of von Kleist

IEEE Spectrum is a magazine edited by the Institute of Electrical and Electronics Engineers. ... ISSN, or International Standard Serial Number, is the unique eight-digit number applied to a periodical publication including electronic serials. ... Motto Satyameva Jayate (Sanskrit)  (Devanagari) Truth Alone Triumphs[1] Anthem Jana Gana Mana Thou art the ruler of the minds of all people[2] Vande Mataram I bow to thee, Mother[4] Capital New Delhi Largest city Mumbai Official Languages: Scheduled Languages: Hindi, English Hindi in the Devanagari script is...

External links

Wikimedia Commons has media related to:

Capacitors

• The Capacitor Tutorial
• Capacitance and Inductance - a chapter from an online textbook
• Howstuffworks.com: How Capacitors Work
• CapSite 2007: Introduction to Capacitors
• AC circuits
• Capacitor Tutorial - Includes how to read capacitor temperature codes
• Capacitors in Circuits by Ernest Lee, The Wolfram Demonstrations Project.