In practical terms, the ampere is a measure of the amount of electric charge passing a point in an electric circuit per unit time with 6. 241 × 10 < sup > 18 </ sup > electrons, or one coulomb per second constituting one ampere.

The SI unit of charge, the coulomb, " is the quantity of electricity carried in 1 second by a current of 1 ampere ".

Conversely, a current of one ampere is one coulomb of charge going past a given point per second:

Since a coulomb is approximately equal to elementary charges ( such as electrons ), one ampere is approximately equivalent to elementary charges moving past a boundary in one second, or the reciprocal of the value of the elementary charges in coulombs.

The SI unit for measuring the rate of flow of electric charge is the ampere, which is charge flowing through some surface at the rate of one coulomb per second.

The amount of charge is usually given the symbol Q and expressed in coulombs ; each electron carries the same charge of approximately − 1. 6022 × 10 < small >< sup >− 19 </ sup ></ small > coulomb.

The proton has a charge that is equal and opposite, and thus + 1. 6022 × 10 < small >< sup >− 19 </ sup ></ small > coulomb.

It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity.

The unit of capacitance is the farad, named after Michael Faraday, and given the symbol F: one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb.

Thus it is 1 volt ( 1 joule per coulomb, 1 J / C ) multiplied by the electron charge ( 1 e, or ).

The SI unit of electric charge is the coulomb ( C ), although in electrical engineering it is also common to use the ampere-hour ( Ah ), and in chemistry it is common to use the elementary charge ( e ) as a unit.

The SI unit of quantity of electric charge is the coulomb, which is equivalent to about ( e is the charge of a proton ).

One illustrative example of a two-body interaction where this form would not apply is for electrostatic potentials due to charged particles, because they certainly do interact with each other by the coulomb interaction ( electrostatic force ), shown below.

If the ion energy is sufficiently high ( usually tens of MeV ) to overcome the coulomb barrier, there can even be a small amount of nuclear transmutation.

It is also equal to the potential difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb.

Additionally, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it.

The practical definition may lead to confusion with the definition of a coulomb ( i. e., 1 amp-second ), but in practical terms this means that measures of a constant current ( e. g., the nominal flow of charge per second through a simple circuit ) will be defined in amperes ( e. g., " a 20 mA circuit ") and the flow of charge through a circuit over a period of time will be defined in coulombs ( e. g., " a variable-current circuit that flows a total of 10 coulombs over 5 seconds ").

The strength or magnitude of the field at a given point is defined as the force that would be exerted on a positive test charge of 1 coulomb placed at that point ; the direction of the field is given by the direction of that force.

In the SI system, the coulomb is defined in terms of the ampere and second: 1C = 1A × 1s.

One now adds the requirement that one wants force to be measured in newtons, distance in metres, and charge to be measured in the engineers ' practical unit, the coulomb, which is defined as the charge accumulated when a current of 1 ampere flows for one second.

In SI, a separate base unit ( the ampere ) is associated with electrical phenomena, with the consequence that something like electrical charge ( 1 coulomb = 1 ampere × 1 second ) is a unique dimension of physical quantity and is not expressed purely in terms of the mechanical units ( kilogram, metre, second ).

* coulomb ( electric charge )

* The work required to move an electric charge of one coulomb through an electrical potential difference of one volt, or one '" coulomb volt " ( C · V ).

File: Coulomb. jpg | Charles-Augustin de Coulomb ( 1736-1806 ): formulated a law in 1785 which described the electrostatic interaction between electrically charged particles ( attraction and repulsion ) and was essential to the development of the theory of electromagnetism, namesake of the unit of electric charge: the coulomb ( C )

= charge of an electron ( coulomb )

* The coulomb per kilogram ( C / kg ) is the SI unit of ionizing radiation exposure, and it is the amount of radiation required to create one coulomb of charge of each polarity in one kilogram of matter.

The electric potential can be calculated at a point in either a static ( time-invariant ) electric field or in a dynamic ( varying with time ) electric field at a specific time, and has the units of joules per coulomb, or volts.

Like other measures of energy per charge, emf has SI units of volts, equivalent to joules per coulomb.

Since the photon has no mass, the coulomb potential has an infinite range.

Electrical flux has SI units of volt metres ( V m ), or, equivalently, newton metres squared per coulomb.

In principle, one has a choice of deciding whether to make the coulomb or the ampere the fundamental unit of electricity and magnetism.

This is the case in ordinary metallic wires and in metal film resistors, where shot noise is almost completely cancelled due to this anti-correlation between the motion of individual electrons, acting on each other through the coulomb force.

A particle carrying a charge of 1 coulomb and passing through a magnetic field of 1 tesla at a speed of 1 meter per second perpendicular to said field experiences a force of 1 newton, according to the Lorentz force law.

In recognition of his contribution to the creation of modern electrical science, an international convention signed in 1881 established the ampere as a standard unit of electrical measurement, along with the coulomb, volt, ohm, and watt, which are named, respectively, after Ampère ’ s contemporaries Charles-Augustin de Coulomb of France, Alessandro Volta of Italy, Georg Ohm of Germany, and James Watt of Scotland.

* One coulomb is the magnitude ( absolute value ) of electrical charge in protons or electrons.

The SI unit of capacitance is the farad ( named after the English physicist Michael Faraday ); a 1 farad capacitor when charged with 1 coulomb of electrical charge will have a potential difference of 1 volt between its plates.

The daraf is the unit of electrical elastance ( symbol: F < sup >− 1 </ sup >), the voltage across a capacitor after accepting an electric charge of 1 coulomb ; it is the reciprocal of the farad.

* C, the conventional electrical unit for the coulomb

** the unit coulomb of electrical charge

Practical applications and advances in such fields created an increasing need for standardized units of measure ; it led to the international standardization of the units ohm, volt, ampere, coulomb, and watt.

For example, one possible proposed redefinition is " the ampere ... is such that the value of the elementary charge e ( charge on a proton ) is exactly 1. 602176487 × 10 < sup >− 19 </ sup > coulomb " This proposal is not yet accepted as part of the SI system: The SI definitions are unlikely to change until at least 2015.

A coulomb is 1 ampere second.

The metric units ampere, volt, ohm and coulomb are the only units used.

This group also recognized that any one of the practical units already in use ( ohm, ampere, volt, henry, farad, coulomb, and weber ), could equally serve as the fourth fundamental unit.