# Coulomb's law

Coulomb forceelectrostatic forceCoulomb interactionCoulomb repulsionelectrostatic attractionCoulombicelectric forceCoulombelectrostatic forceselectrostatic
Coulomb's law, or Coulomb's inverse-square law, is an experimental law of physics that quantifies the amount of force between two stationary, electrically charged particles.wikipedia
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### Charles-Augustin de Coulomb

CoulombCharles CoulombCharles Augustin de Coulomb
The law was first published in 1785 by French physicist Charles-Augustin de Coulomb, and was essential to the development of the theory of electromagnetism, maybe even its starting point, because it was now possible to discuss quantity of electric charge in a meaningful way.
He is best known as the eponymous discoverer of what is now called Coulomb's law, the description of the electrostatic force of attraction and repulsion, though he also did important work on friction.

### Coulomb constant

Coulomb's constantCoulomb force constantelectrostatic constant
where k is Coulomb's constant (k ≈ 9e9 N⋅m⋅C), q and q are the signed magnitudes of the charges, and the scalar r is the distance between the charges.
It was named after the French physicist Charles-Augustin de Coulomb (1736–1806) who introduced Coulomb's law.

### Gauss's law

Gauss' lawGauss lawGauss
Coulomb's law can be used to derive Gauss's law, and vice versa.
Gauss's law can be used to derive Coulomb's law, and vice versa.

### Electricity

electricalelectricelectrically
Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity.
The magnitude of this force is given by Coulomb's law.

### Newton's law of universal gravitation

law of universal gravitationuniversal gravitationNewtonian gravity
Being an inverse-square law, the law is analogous to Isaac Newton's inverse-square law of universal gravitation, but gravitational forces are always attractive, while electrostatic forces can be attractive or repulsive. Based on experiments with electrically charged spheres, Joseph Priestley of England was among the first to propose that electrical force followed an inverse-square law, similar to Newton's law of universal gravitation.
Newton's law of gravitation resembles Coulomb's law of electrical forces, which is used to calculate the magnitude of the electrical force arising between two charged bodies.

### Henry Cavendish

CavendishCavendish balanceCavendish, Henry
In the early 1770s, the dependence of the force between charged bodies upon both distance and charge had already been discovered, but not published, by Henry Cavendish of England.
A notoriously shy man, Cavendish was nonetheless distinguished for great accuracy and precision in his researches into the composition of atmospheric air, the properties of different gases, the synthesis of water, the law governing electrical attraction and repulsion, a mechanical theory of heat, and calculations of the density (and hence the mass) of the Earth.

### Inverse-square law

inverse square lawinverse squareinverse-square
Being an inverse-square law, the law is analogous to Isaac Newton's inverse-square law of universal gravitation, but gravitational forces are always attractive, while electrostatic forces can be attractive or repulsive. Based on experiments with electrically charged spheres, Joseph Priestley of England was among the first to propose that electrical force followed an inverse-square law, similar to Newton's law of universal gravitation.
The force of attraction or repulsion between two electrically charged particles, in addition to being directly proportional to the product of the electric charges, is inversely proportional to the square of the distance between them; this is known as Coulomb's law.

### Classical electromagnetism

classical electrodynamicselectrodynamicsclassical
The law was first published in 1785 by French physicist Charles-Augustin de Coulomb, and was essential to the development of the theory of electromagnetism, maybe even its starting point, because it was now possible to discuss quantity of electric charge in a meaningful way.
In electrostatics, where charges are not moving, around a distribution of point charges, the forces determined from Coulomb's law may be summed.

### Scientific law

laws of physicsphysical lawlaws of nature
Coulomb's law, or Coulomb's inverse-square law, is an experimental law of physics that quantifies the amount of force between two stationary, electrically charged particles.

### Capacitor

capacitorscapacitivecondenser
Early investigators of the 18th century who suspected that the electrical force diminished with distance as the force of gravity did (i.e., as the inverse square of the distance) included Daniel Bernoulli and Alessandro Volta, both of whom measured the force between plates of a capacitor, and Franz Aepinus who supposed the inverse-square law in 1758.
From Coulomb's law a charge on one conductor will exert a force on the charge carriers within the other conductor, attracting opposite polarity charge and repelling like polarity charges, thus an opposite polarity charge will be induced on the surface of the other conductor.

### Electric charge

chargeelectrical chargecharged
Coulomb's law, or Coulomb's inverse-square law, is an experimental law of physics that quantifies the amount of force between two stationary, electrically charged particles. Based on experiments with electrically charged spheres, Joseph Priestley of England was among the first to propose that electrical force followed an inverse-square law, similar to Newton's law of universal gravitation.
Coulomb's law quantifies the electrostatic force between two particles by asserting that the force is proportional to the product of their charges, and inversely proportional to the square of the distance between them.

### Relative permittivity

dielectric constantrelative static permittivityrelative dielectric constant
, which is the dimensionless relative permittivity of the material in which the charges are immersed, or with their product
Permittivity is a material property that affects the Coulomb force between two point charges in the material.

### Joseph Priestley

PriestleyJoseph PriestlyPriestly
Based on experiments with electrically charged spheres, Joseph Priestley of England was among the first to propose that electrical force followed an inverse-square law, similar to Newton's law of universal gravitation.
However, he did not generalise or elaborate on this, and the general law was enunciated by French physicist Charles-Augustin de Coulomb in the 1780s.

### John Robison (physicist)

John RobisonProfessor John RobisonProf. John Robison
In 1769, Scottish physicist John Robison announced that, according to his measurements, the force of repulsion between two spheres with charges of the same sign varied as
In 1769, he announced that balls with like electrical charges repel each other with a force that varies as the inverse-square of the distance between them, anticipating Coulomb's law of 1785.

### Force

forcesattractiveelastic force
Early investigators of the 18th century who suspected that the electrical force diminished with distance as the force of gravity did (i.e., as the inverse square of the distance) included Daniel Bernoulli and Alessandro Volta, both of whom measured the force between plates of a capacitor, and Franz Aepinus who supposed the inverse-square law in 1758.
The electrostatic force was first described in 1784 by Coulomb as a force that existed intrinsically between two charges.

### Electric field

electricelectrostatic fieldelectrical field
By choosing one of the point charges to be the source, and the other to be the test charge, it follows from Coulomb's law that the magnitude of the electric field
The electric field is defined mathematically as a vector field that associates to each point in space the (electrostatic or Coulomb) force per unit of charge exerted on an infinitesimal positive test charge at rest at that point.

### Gaussian units

Gaussiancgs-Gaussian unitsGaussian-cgs units
Gaussian units and Lorentz–Heaviside units are both CGS unit systems.
On the other hand, the inverse-square force laws – Coulomb's law and the Biot–Savart law – do have a factor of 4π attached to the r 2.

### Electrostatics

electrostaticelectrostatic repulsionelectrostatic interactions
The last of these is known as the electrostatic approximation.
Such forces are described by Coulomb's law.

### Precision tests of QED

extremely accurate predictionstesthigh-precision atomic tests of quantum electrodynamics
The law has been tested extensively, and observations have upheld the law on a scale from 10 −16 m to 10 8 m.

### Point particle

point chargepoint massparticle
He used a torsion balance to study the repulsion and attraction forces of charged particles, and determined that the magnitude of the electric force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
The fundamental equation of electrostatics is Coulomb's law, which describes the electric force between two point charges.

### Torsion spring

torsion balancetorsion pendulumtorsion coefficient
He used a torsion balance to study the repulsion and attraction forces of charged particles, and determined that the magnitude of the electric force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
Its most well-known uses were by Coulomb to measure the electrostatic force between charges to establish Coulomb's Law, and by Henry Cavendish in 1798 in the Cavendish experiment to measure the gravitational force between two masses to calculate the density of the Earth, leading later to a value for the gravitational constant.

### Vacuum permittivity

permittivity of free spaceelectric constantvacuum electric permittivity
is the vacuum electric permittivity (also known as "electric constant") in C 2 ⋅m −2 ⋅N −1.
For example, the force between two separated electric charges (in the vacuum of classical electromagnetism) is given by Coulomb's law:

### Centimetre–gram–second system of units

CGScgs unitsCGS unit
Gaussian units and Lorentz–Heaviside units are both CGS unit systems.
It is done by setting the Coulomb force constant, so that Coulomb's law does not contain an explicit prefactor.

### Natural units

natural unitGeometric variableshas been set to one
The Lagrangian of quantum electrodynamics is normally written in natural units, but in SI units, it is:
There are two common ways to relate charge to mass, length, and time: In Lorentz–Heaviside units (also called "rationalized"), Coulomb's law is

### Fine-structure constant

fine structure constant137coupling constant
For various reasons, it is more convenient to define the fine-structure constant, and then define.
In electrostatic cgs units, the unit of electric charge, the statcoulomb, is defined so that the Coulomb constant,