The centimetre-gram-second system (CGS) is a system of physical units. It is always the same for mechanical units, but there are several variants of electric additions. Its main counterpart is the MKS, or meter-kilogram-second system. An expert is someone widely recognized as a reliable source of knowledge, technique, or skill whose judgment is accorded authority and status by the public or their peers. ... // Introduction The definition, agreement and practical use of units of measurement have played a crucial role in human endeavour from early ages up to this day. ... Cover of brochure The International System of Units. ...

The system goes back to a proposal made in 1832 by the German mathematician Carl Friedrich Gauss and was in 1874 extended by the British physicists James Clerk Maxwell and William Thomson with a set of electromagnetic units. The sizes (order of magnitude) of many CGS units turned out to be inconvenient for practical purposes, therefore the CGS system never gained wide general use outside the field of electrodynamics and was gradually superseded internationally starting in the 1880s but not to a significant extent until the mid-20th century by the more practical MKS (metre-kilogram-second) system, which led eventually to the modern SI standard units. In general English usage, length (symbols: l, L) is but one particular instance of distance – an objects length is how long the object is – but in the physical sciences and engineering, the word length is in some contexts used synonymously with distance. Height is vertical distance; width (or breadth... The metre, or meter (symbol: m) is the SI base unit of length. ... Mass is a property of a physical object that quantifies the amount of matter it contains. ... The gram or gramme, symbol g, is a unit of mass. ... Watches are used to measure time Time has long been a major subject of philosophy, art, poetry, and science. ... Look up second in Wiktionary, the free dictionary. ... In physics, a net force acting on a body causes that body to accelerate; that is, to change its velocity. ... In physics, the dyne is a unit of force specified in the centimetre-gram-second (cgs) system of units, symbol dyn. One dyne is equal to exactly 10-5 newtons. ... The newton (symbol: N) is the SI unit of force. ... An erg is the unit of energy and mechanical work in the centimetre-gram-second (CGS) system of units, symbol erg. Its name is derived from the Greek word meaning work. The erg is a quite small unit, equal to a force of one dyne exerted for a distance of... The joule (symbol: J) is the SI unit of energy, or work with base units of kg·m2/s2. ... In physics, power (symbol: P) is the amount of work done per unit of time. ... The watt (symbol: W) is the SI derived unit of power. ... Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... The barye (symbol: Ba) is the centimetre-gram-second (CGS) unit of pressure. ... The pascal (symbol: Pa) is the SI unit of pressure. ... Bold text The pitch drop experiment at the University of Queensland. ... The poise (P) is the cgs unit of viscosity, 1 P = 1 g·cm-1·s-1 The SI analog is 1 pascal second (Pa·s) = 1 kg·m-1·s-1 = 10 P. It is named after Jean Louis Marie Poiseuille. ... The pascal second (symbol Pa·s) is the SI unit of dynamic viscosity. ... 1832 was a leap year starting on Sunday (see link for calendar). ... (help· info) (30 April 1777 – 23 February 1855) was a German mathematician and scientist of profound genius who contributed significantly to many fields, including number theory, analysis, differential geometry, geodesy, magnetism, astronomy and optics. ... 1874 (MDCCCLXXIV) was a common year starting on Thursday (see link for calendar). ... James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematical physicist, born in Edinburgh. ... The Right Honourable William Thomson, 1st Baron Kelvin, GCVO, OM, PC, PRS (26 June 1824–17 December 1907) was a Irish-Scottish mathematical physicist and engineer, an outstanding leader in the physical sciences of the 19th century. ... // Events and Trends Technology Development and commercial production of electric lighting Development and commercial production of gasoline-powered automobile by Karl Benz, Gottlieb Daimler and Maybach First commercial production and sales of phonographs and phonograph recordings. ... Cover of brochure The International System of Units. ...

CGS units are still occasionally encountered in older technical literature, especially in the United States in the fields of electrodynamics and astronomy. SI units were chosen such that electromagnetic equations concerning spheres contain 4π, those concerning coils contain 2π and those dealing with straight wires lack π entirely, which was the most convenient choice for electrical-engineering applications. In those fields where formulas concerning spheres dominate (for example, astronomy), it has been argued that the CGS system can be notationally slightly more convenient. Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... Lunar astronomy: the large crater is Daedalus, photographed by the crew of Apollo 11 as they circled the Moon in 1969. ... Lunar astronomy: the large crater is Daedalus, photographed by the crew of Apollo 11 as they circled the Moon in 1969. ...

Starting from the international adoption of the MKS standard in the 1940s and the SI standard in the 1960s, the technical use of CGS units has gradually disappeared worldwide, in the United States more slowly than in the rest of the world. CGS units are today no longer accepted by the house styles of most scientific journals, textbook publishers and standards bodies. Cover of brochure The International System of Units. ...

The units gram and centimetre remain useful within the SI, especially for instructional physics and chemistry experiments, where they match well the small scales of table-top setups. In these uses, they are occasionally referred to as the system of “LAB” units. However, where derived units are needed, the SI ones are generally used and taught today instead of the CGS ones. Cover of brochure The International System of Units. ...

Electromagnetic units

While for most units the difference between cgs and SI are just powers of 10, the differences in electromagnetic units are considerable; so much so that formulas for physical laws need to be changed depending on what system of units one uses. In SI, electric current is defined via the magnetic force it exerts and charge is then defined as current multiplied with time. In one variant of the cgs system, electrostatic units (esu), charge is defined via the force it exerts on other charges, and current is then defined as charge per time. One consequence of this approach is that Coulomb’s law does not contain a constant of proportionality. Cover of brochure The International System of Units. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, which exerts a force on those particles that possess the property of electric charge, and is in turn affected by the presence and motion of such particles. ... In electricity, current refers to electric current, which is the flow of electric charge. ... In physics, magnetism is one of the phenomena by which materials exert an attractive or repulsive force on other materials. ... Charge is a word with many different meanings. ... The statcoulomb (statC) or franklin (Fr) or electrostatic unit of charge (esu) is the physical unit for electrical charge used in the centimetre-gram-second (cgs) electrostatic system of units. ... 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. ... This article is about proportionality, the mathematical relation. ...

While the proportional constants in cgs simplify theoretical calculations, they have the disadvantage that the units in cgs are hard to define through experiment. SI on the other hand starts with a unit of current, the ampere which is easy to determine through experiment, but which requires that the constants in the electromagnetic equations take on odd forms. Cover of brochure The International System of Units. ... The ampere (symbol: A) is the SI base unit of electric current equal to one coulomb per second. ...

Ultimately, relating electromagnetic phenomena to time, length and mass relies on the forces observed on charges. There are two fundamental laws in action: Coulomb’s law, which describes the electrostatic force between charges, and Ampère’s law (also known as the Biot-Savart law), which describes the electrodynamic (or electromagnetic) force between currents. Each of these includes one proportionality constant, k₁ or k₂. The static definition of magnetic fields yields a third proportionality constant, α. The first two constants are related to each other through the speed of light, c (the ratio of k₁ over k₂ must equal c²). 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. ... An electric current produces a magnetic field. ... The Biot-Savart law is a physical law with applications in both electromagnetics and aerodynamics. ... The word proportionality may have one of a number of meanings: In mathematics, proportionality is a mathematical relation between two quantities. ... Cherenkov effect in a swimming pool nuclear reactor. ...

We then have several choices:

There were at various points in time about half a dozen systems of electromagnetic units in use, most based on the cgs system. These include electromagnetic units (emu, chosen such that the Biot-Savart law has no constant of proportionality), Gaussian, and Heaviside-Lorentz units. A key virtue of the Gaussian CGS system is that electric and magnetic fields have the same units, both ε₀ and μ₀ are 1, and the only dimensional constant appearing in the equations is c, the speed of light. The Heaviside-Lorentz system has these desirable properties as well, but is a "rationalized" system (as is SI) in which the charges and fields are defined in such a way that there are many fewer factors of 4π appearing in the formulas, and it is in Heaviside-Lorentz units that the Maxwell equations take their simplest possible form. CGS is an acronym for centimetre-gram-second. ... The Biot-Savart law is a physical law with applications in both electromagnetics and aerodynamics. ... CGS is an acronym for centimetre-gram-second. ... Maxwells equations are the set of four equations, attributed to James Clerk Maxwell, that describe the behavior of both the electric and magnetic fields, as well as their interactions with matter. ...

Further complicating matters is the fact that some physicists and engineers in the United States use hybrid units, such as volts per centimetre for electric field. However, this also can be seen more as an application of the previously described "LAB" units usage since electric fields near small circuit devices would be measured across distances on the order of magnitude of 1 centimetre. Engineering is the application of scientific and technical knowledge to solve human problems. ... The volt (symbol: V) is the SI derived unit of electric potential difference. ... The metre, or meter (symbol: m) is the SI base unit of length. ...

The mantissas derived from the speed of light are more precisely 299792458, 333564095198152, 1112650056, and 89875517873681764. ‹ The template below has been proposed for deletion. ... The statcoulomb (statC) or franklin (Fr) or electrostatic unit of charge (esu) is the physical unit for electrical charge used in the centimetre-gram-second (cgs) electrostatic system of units. ... The coulomb (symbol: C) is the SI unit of electric charge. ... Electric potential is the potential energy per unit charge associated with a static (time-invariant) electric field, also called the electrostatic potential, typically measured in volts. ... The statvolt is the unit of voltage and electrical potential used in the cgs system of units. ... The volt (symbol: V) is the SI derived unit of electric potential difference. ... In physics, an electric field or E-field is an effect produced by an electric charge (or a time-varying magnetic field) that exerts a force on charged objects in the field. ... In physics, a magnetic field is an entity produced by moving electric charges (electric currents) that exerts a force on other moving charges. ... The oersted is old CGS unit of magnetic field strength (or magnetic induction). ... Magnetic flux, is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... The compound derived CGS unit, the maxwell, abbreviated as Mx, is the unit for the magnetic flux. ... This article is in need of attention. ... Electromagnetic induction is the production of an electrical potential difference (or voltage) across a conductor situated in a changing magnetic field. ... The gauss, abbreviated as G, is the cgs unit of magnetic flux density or magnetic induction (B), named after the German mathematician and physicist Carl Friedrich Gauss. ... The tesla (symbol T) is the SI derived unit of magnetic flux density (or magnetic induction). ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... The ohm (symbol: Ω) is the SI unit of electric resistance. ... // Headline text POOP!! Danny Hornsby (also known as Gnome) is a measure indicating how strongly a Gnome can opposes the flow of electric current. ... Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... The farad (symbol: F) is the SI unit of capacitance. ... // Definition Inductance is a measure of the amount of magnetic flux produced for a given electric current. ... The henry (symbol: H) is the SI unit of inductance. ... The significand (also coefficient or, more informally, mantissa) is the part of a floating-point number that contains its significant digits. ... Cherenkov effect in a swimming pool nuclear reactor. ...

A centimetre of capacitance is the capacitance between a sphere of radius 1 cm in vacuum and infinity. The capacitance C between two spheres of radii R and r is

.

By taking the limit as R goes to infinity we see C equals r.

See also

• Scientific units named after people
• Metric system
• Units of measurement