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Encyclopedia > Electric charge
Electromagnetism
Electricity · Magnetism
Electrostatics
Electric charge
Coulomb's law
Electric field
Gauss's law
Electric potential
Electric dipole moment
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Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields. The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the four fundamental forces. CPT-symmetry is a fundamental symmetry of physical laws under transformations that involve the inversions of charge, parity and time simultaneously. ... In the standard model of particle physics the Cabibbo Kobayashi Maskawa matrix (CKM matrix, sometimes earlier called KM matrix) is a unitary matrix which contains information on the strength of flavour changing weak decays. ... CP is the product of two symmetries: C for charge conjugation, which transforms a particle into its antiparticle, and P for parity, which creates the mirror image of a physical system. ... A phenomenon is said to be chiral if it is not identical to its mirror image (see Chirality (mathematics)). The spin of a particle may be used to define a handedness for that particle. ... Helium atom (schematic) Showing two protons (red), two neutrons (green) and two electrons (yellow). ... Electromagnetic interaction is a fundamental force of nature and is felt by charged leptons and quarks. ... The electromagnetic field is a physical field that is produced by electrically charged objects and which affects the behaviour of charged objects in the vicinity of the field. ... In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ...

Electric charge is a characteristic of some subatomic particles, and is quantized when expressed as a multiple of the so-called elementary charge e. Electrons by convention have a charge of -1, while protons have the opposite charge of +1. Quarks have a fractional charge of −1/3 or +2/3. The antiparticle equivalents of these have the opposite charge. There are other charged particles. The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... For other uses, see Electron (disambiguation). ... For other uses, see Proton (disambiguation). ... For other uses, see Quark (disambiguation). ... Corresponding to most kinds of particle, there is an associated antiparticle with the same mass and opposite charges. ... In physics, a charged particle is a particle with an electric charge. ...

In general, same-sign charged particles repel one another, while different-sign charged particles attract. This is expressed quantitatively in Coulomb's law, which states the magnitude of the repelling force is proportional to the product of the two charges, and weakens proportionately to the square of the distance. Coulombs torsion balance In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrostatic force that one stationary, electrically charged object of small dimensions (ideally, a point source) exerts on another. ...

The electric charge of a macroscopic object is the sum of the electric charges of its constituent particles. Often, the net electric charge is zero, since naturally the number of electrons in every atom is equal to the number of the protons, so their charges cancel out. Situations in which the net charge is non-zero are often referred to as static electricity. Furthermore, even when the net charge is zero, it can be distributed non-uniformly (e.g., due to an external electric field), and then the material is said to be polarized, and the charge related to the polarization is known as bound charge (while the excess charge brought from outside is called free charge). An ordered motion of charged particles in a particular direction (in metals, these are the electrons) is known as electric current. The discrete nature of electric charge was proposed by Michael Faraday in his electrolysis experiments, then directly demonstrated by Robert Millikan in his oil-drop experiment. Macroscopic is commonly used to describe physical objects that are measurable and observable by the naked eye. ... Properties For other meanings of Atom, see Atom (disambiguation). ... For alternative meanings see proton (disambiguation). ... Static electricity is a class of phenomena involving the net charge present on an object; typically referring to charged object with voltages of sufficient magnitude to produce visible attraction, repulsion, and sparks. ... 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 electrostatics, the polarization is the vector field that results from permanent or induced electric dipole moments in a dielectric material. ... In classical electromagnetism, the polarization density (or electric polarization, or simply polarization) is the vector field that expresses the density of permanent or induced electric dipole moments in a dielectric material. ... Electric current is the flow (movement) of electric charge. ... Michael Faraday, FRS (September 22, 1791 â€“ August 25, 1867) was an English chemist and physicist (or natural philosopher, in the terminology of that time) who contributed to the fields of electromagnetism and electrochemistry. ... Robert Andrews Millikan (March 22, 1868 â€“ December 19, 1953) was an American experimental physicist who won the 1923 Nobel Prize for his measurement of the charge on the electron and for his work on the photoelectric effect. ... The purpose of Robert Millikan and Harvey Fletchers oil-drop experiment (1909) was to measure the electric charge of the electron. ...

The SI unit for quantity of electricity or electric charge is the coulomb, which represents approximately 6.24 × 1018 elementary charges (the charge on a single electron or proton). The coulomb is defined as the quantity of charge that has passed through the cross-section of an electrical conductor carrying one ampere within one second. The symbol Q is often used to denote a quantity of electricity or charge. The quantity of electric charge can be directly measured with an electrometer, or indirectly measured with a ballistic galvanometer. Look up si, Si, SI in Wiktionary, the free dictionary. ... In physics the term quantity of electricity refers to the quantity of electric charge. ... The coulomb (symbol: C) is the SI unit of electric charge. ... The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... In science and engineering, conductors, such as copper or aluminum, are materials with atoms having loosely held valence electrons. ... For other uses, see Ampere (disambiguation). ... An electrometer is an electrical instrument for measuring electric charge or electrical potential difference. ... Wire carrying current to be measured Restoring spring N and S are poles of magnet A galvanometer is a type of ammeter â€” an instrument for detecting and measuring electric current. ...

Formally, a measure of charge should be a multiple of the elementary charge e (charge is quantized), but since it is an average, macroscopic quantity, many orders of magnitude larger than a single elementary charge, it can effectively take on any real value. Furthermore, in some contexts it is meaningful to speak of fractions of a charge; e.g. in the charging of a capacitor. Generally, quantization is the state of being constrained to a set of discrete values, rather than varying continuously. ... Macroscopic is commonly used to describe physical objects that are measurable and observable by the naked eye. ... In mathematics, the real numbers may be described informally as numbers that can be given by an infinite decimal representation, such as 2. ... See Capacitor (component) for a discussion of specific types. ...

## Contents

Coulomb's torsion balance

As reported by the Ancient Greek philosopher Thales of Miletus around 600 BC, charge (or electricity) could be accumulated by rubbing fur on various substances, such as amber. The Greeks noted that the charged amber buttons could attract light objects such as hair. They also noted that if they rubbed the amber for long enough, they could even get a spark to jump. This property derives from the triboelectric effect. Image File history File links Bcoulomb. ... Image File history File links Bcoulomb. ... For the French electronics and defence contractor, see Thales Group Thales (in Greek: &#920;&#945;&#955;&#951;&#962;) of Miletus (circa 635 BC - 543 BC), also known as Thales the Milesian, was a pre-Socratic Greek philosopher and one of the Seven Sages of Greece. ... Centuries: 8th century BC - 7th century BC - 6th century BC Decades: 650s BC 640s BC 630s BC 620s BC 610s BC - 600s BC - 590s BC 580s BC 570s BC 560s BC 550s BC The 600s BC are the years 609 to 600 BC. Events and trends 609 BC - King Josiah... For other uses, see Fur (disambiguation). ... For other uses, see Amber (disambiguation). ... For the 1968 stage production, see Hair (musical), for the 1979 film, see Hair (film). ... For other uses, see Amber (disambiguation). ... The triboelectric effect is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated (such as through rubbing). ...

In 1600 the English scientist William Gilbert returned to the subject in De Magnete, and coined the New Latin word electricus from ηλεκτρον (elektron), the Greek word for "amber", which soon gave rise to the English words "electric" and "electricity." He was followed in 1660 by Otto von Guericke, who invented what was probably the first electrostatic generator. Other European pioneers were Robert Boyle, who in 1675 stated that electric attraction and repulsion can act across a vacuum; Stephen Gray, who in 1729 classified materials as conductors and insulators; and C. F. du Fay, who proposed in 1733 [2] that electricity came in two varieties which cancelled each other, and expressed this in terms of a two-fluid theory. When glass was rubbed with silk, du Fay said that the glass was charged with vitreous electricity, and when amber was rubbed with fur, the amber was said to be charged with resinous electricity. In 1839 Michael Faraday showed that the apparent division between static electricity, current electricity and bioelectricity was incorrect, and all were a consequence of the behavior of a single kind of electricity appearing in opposite polarities. It is arbitrary which polarity you call positive and which you call negative. Positive charge can be defined as the charge left on a glass rod after being rubbed with silk.[1] 1600 was a leap year starting on Saturday of the Gregorian calendar (or a leap year starting on Tuesday of the 10-day slower Julian calendar). ... For other persons named William Gilbert, see William Gilbert (disambiguation). ... New Latin (or Neo-Latin) is a post-medieval version of Latin, now used primarily in International Scientific Vocabulary cladistics and systematics. ... // Events January 1 - Colonel George Monck with his regiment crosses from Scotland to England at the village of Coldstream and begins advance towards London in support of English Restoration. ... Otto von Guericke Otto von Guericke (originally spelled Gericke) [] (November 20, 1602 â€“ May 11, 1686 (Julian calendar); November 30, 1602 â€“ May 21, 1686 (Gregorian calendar)) was a German scientist, inventor, and politician. ... Electrostatics is the branch of physics that deals with the force exerted by a static (i. ... Robert Boyle (Irish: Robaird Ã“ Bhaoill) (25 January 1627 â€“ 30 December 1691) was an Irish natural philosopher, chemist, physicist, inventor, and early gentleman scientist, noted for his work in physics and chemistry. ... Year 1675 (MDCLXXV) was a common year starting on Tuesday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Friday of the 10-day slower Julian calendar). ... This article or section does not cite any references or sources. ... Events July 30 - Baltimore, Maryland is founded. ... In science and engineering, conductors, such as copper or aluminum, are materials with atoms having loosely held valence electrons. ... This article or section is in need of attention from an expert on the subject. ... Charles François de Cisternay du Fay (Paris, 1698 - 1739) was a French scientist and superintendent of the Jardin du Roi. ... Events February 12 - British colonist James Oglethorpe founds Savannah, Georgia. ... 1839 (MDCCCXXXIX) was a common year starting on Tuesday (see link for calendar). ...

One of the foremost experts on electricity in the 18th century was Benjamin Franklin, who argued in favour of a one-fluid theory of electricity. Franklin imagined electricity as being a type of invisible fluid present in all matter; for example he believed that it was the glass in a Leyden jar that held the accumulated charge. He posited that rubbing insulating surfaces together caused this fluid to change location, and that a flow of this fluid constitutes an electric current. He also posited that when matter contained too little of the fluid it was "negatively" charged, and when it had an excess it was "positively" charged. Arbitrarily (or for a reason that was not recorded) he identified the term "positive" with vitreous electricity and "negative" with resinous electricity. William Watson arrived at the same explanation at about the same time. (17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ... Benjamin Franklin (January 17 [O.S. January 6] 1706 â€“ April 17, 1790) was one of the most well known Founding Fathers of the United States. ... This article is about the material. ... Original capacitor The Leyden jar is a device for storing electric charge invented in 1745 by Pieter van Musschenbroek (1700â€“1748). ... William Watson (3 April 1715 â€“ 10 May 1787) was an English physician and scientist who was born and died in London. ...

We now know that the Franklin/Watson model was fundamentally correct. There is only one kind of electrical charge, and only one variable is required to keep track of the amount of charge.[2] On the other hand, just knowing the charge is not a complete description of the situation. Matter is composed of several kinds of electrically charged particles, and these particles have many properties, not just charge.

The most common charge carriers are the positively charged proton and the negatively charged electron. The movement of any of these charged particles constitutes an electric current. In many situations, it suffices to speak of the conventional current without regard to whether it is carried by positive charges moving in the direction of the conventional current and/or by negative charges moving in the opposite direction. This macroscopic viewpoint is an approximation that simplifies electromagnetic concepts and calculations. For other uses, see Proton (disambiguation). ... For other uses, see Electron (disambiguation). ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ...

Beware that in the common and important case of metallic wires, the direction of the conventional current is opposite to the drift velocity of the actual charge carriers, i.e. the electrons. This is a source of confusion for beginners.

## Properties

Aside from the properties described in articles about electromagnetism, charge is a relativistic invariant. This means that any particle that has charge q, no matter how fast it goes, always has charge q. This property has been experimentally verified by showing that the charge of one helium nucleus (two protons and two neutrons bound together in a nucleus and moving around at high speeds) is the same as two deuterium nuclei (one proton and one neutron bound together, but moving much more slowly than they would if they were in a helium nucleus). Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... Two-dimensional analogy of space-time curvature described in General Relativity. ... In physics, invariants are usually quantities conserved (unchanged) by the symmetries of the physical system. ... For other uses, see Helium (disambiguation). ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... For other uses, see Proton (disambiguation). ... This article or section does not adequately cite its references or sources. ... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ...

## Conservation of charge

The total electric charge of an isolated system remains constant regardless of changes within the system itself. This law is inherent to all processes known to physics and can be derived in a local form from gauge invariance of the wave function. The conservation of charge results in the charge-current continuity equation. More generally, the net change in charge density ρ within a volume of integration V is equal to the area integral over the current density J on the surface of the area S, which is in turn equal to the net current I: In thermodynamics, an isolated system, as contrasted with a closed system, is a physical system that does not interact with its surroundings. ... Gauge theories are a class of physical theories based on the idea that symmetry transformations can be performed locally as well as globally. ... A wave function is a mathematical tool that quantum mechanics uses to describe any physical system. ... All the examples of continuity equations below express the same idea; they are all really examples of the same concept. ... Charge density is the amount of electric charge per unit volume. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... In electricity, current refers to electric current, which is the flow of electric charge. ...

$- frac{d}{dt} int_V rho, mathrm{d}V = int_S mathbf{J} cdot mathrm{d}mathbf{S} = int J S costheta = I.$

Thus, the conservation of electric charge, as expressed by the continuity equation, gives the result:

$I = -frac{dQ}{dt}$

where I is the net outward current through a closed surface and Q is the electric charge contained within the volume defined by the surface.

In physics, a charge may refer to one of many different quantities, such as the electric charge in electromagnetism or the color charge in quantum chromodynamics. ... Electricity (from New Latin Ä“lectricus, amberlike) is a general term for a variety of phenomena resulting from the presence and flow of electric charge. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... Electrostatic discharge (ESD) is the sudden and momentary electric current that flows between two objects at different electrical potentials. ... ... In physics the term quantity of electricity refers to the quantity of electric charge. ...

1. ^ Electromagnetic Fields (2nd Edition), Roald K. Wangsness, Wiley, 1986. ISBN 0-471-81186-6 (intermediate level textbook)
2. ^ One Kind of Charge [1]

Results from FactBites:

 THE P ZONE - Electric Charge (320 words) The property of electric charge is much the same with certain subatomic particles, and experimental evidence leads us to the conclusion that there are two types of charges. The magnitudes of the electric charges on the election and the proton are equal, but their natures are unlike, as expresses by the plus and minus sign. The unit of electric charge is called the coulomb (C), and was named after Charles Coulomb, the French scientist who studied electrical effects.
 Kids.Net.Au - Encyclopedia > Electric charge (509 words) The interaction between charge and an electromagnetic field is the source of one of the four fundamental forces. Charge was discovered by the Ancient Greeks who found that rubbing fur on various substances, such as amber, would build up an electric charge imbalance. Arbitrarily (or for a reason that was not recorded) he identified the term "positive" with the type of charge acquired by a glass rod rubbed with silk, and "negative" with that acquired by an amber rod rubbed with fur.
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