Charles-Augustin de Coulomb

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Charles-Augustin de Coulomb
Charles de Coulomb.png
Portrait by Louis Hierle in 1894
Born(1736-06-14)14 June 1736
Died23 August 1806(1806-08-23) (aged 70)
Alma mater École royale du génie de Mézières
Known for Coulomb's law

Charles-Augustin de Coulomb ( /ˈklɒm, -lm, kˈlɒm, -ˈlm/ ; [1] French:  [kulɔ̃] ; 14 June 1736 – 23 August 1806) was a French military engineer and physicist. He is best known for developing what is now known as Coulomb's law, the description of the electrostatic force of attraction and repulsion, but also did important work on friction.

Kingdom of France kingdom in Western Europe from 843 to 1791

The Kingdom of France was a medieval and early modern monarchy in Western Europe. It was one of the most powerful states in Europe and a great power since the Late Middle Ages and the Hundred Years' War. It was also an early colonial power, with possessions around the world.

Physicist scientist who does research in physics

A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of physical phenomena and the analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies.

Coulombs law Fundamental physical law of electromagnetism

Coulomb's law, or Coulomb's inverse-square law, is a law of physics for quantifying Coulomb's force, or electrostatic force. Electrostatic force is the amount of force with which stationary, electrically charged particles either repel, or attract each other. This force and the law for quantifying it, represent one of the most basic forms of force used in the physical sciences, and were an essential basis to the study and development of the theory and field of classical electromagnetism. The law was first published in 1785 by French physicist Charles-Augustin de Coulomb.


The SI unit of electric charge, the coulomb, was named in his honour in 1908. [2]

Electric charge physical property that quantifies an objects interaction with electric fields

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charges; positive and negative. Like charges repel and unlike attract. An object with an absence of net charge is referred to as neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum effects.


Charles-Augustin de Coulomb was born in Angoulême, Angoumois county, France, to Henry Coulomb, an inspector of the royal demesne originally from Montpellier, and Catherine Bajet. He was baptised at the parish church of St. André. The family moved to Paris early in his childhood, and he studied at Collège Mazarin. His studies included philosophy, language and literature. He also received a good education in mathematics, astronomy, chemistry and botany. When his father suffered a financial setback, he was forced to leave Paris, and went to Montpellier. Coulomb submitted his first publication to the Society of Sciences in Montpellier during this time. He went back to Paris and passed the exams for the École royale du génie de Mézières in 1760.

Angoulême Prefecture and commune in Nouvelle-Aquitaine, France

Angoulême is a commune, the capital of the Charente department, in the Nouvelle-Aquitaine region of southwestern France.

Angoumois Place in France

Angoumois or equally historically the comté d'Angoulême was a county and province of France, originally inferior to the parent duchy of Aquitaine, similar to the Périgord to its east but lower and generally less forested, equally with occasional vineyards throughout. Its capital was Angoulême with its citadel and castle above the River Charente.

The crown lands, crown estate, royal domain or domaine royal of France refers to the lands, fiefs and rights directly possessed by the kings of France. While the term eventually came to refer to a territorial unit, the royal domain originally referred to the network of "castles, villages and estates, forests, towns, religious houses and bishoprics, and the rights of justice, tolls and taxes" effectively held by the king or under his domination. In terms of territory, before the reign of Henry IV, the domaine royal did not encompass the entirety of the territory of the kingdom of France and for much of the Middle Ages significant portions of the kingdom were the direct possessions of other feudal lords.

He graduated in 1761 and joined the French army as an engineer in the rank of lieutenant. Over the next twenty years, he was posted to a variety of locations where he was involved in engineering: structural, fortifications, soil mechanics, as well as other fields of engineering. His first posting was to Brest but in February 1764 he was sent to Martinique, in the West Indies, where he was put in charge of building the new Fort Bourbon and this task occupied him until June 1772. His health suffered setbacks during the three years he spent in Martinique that would affect him for the rest of his life.

Martinique Overseas region and department in France

Martinique is an insular region of France located in the Lesser Antilles of the West Indies in the eastern Caribbean Sea, with a land area of 1,128 square kilometres (436 sq mi) and a population of 376,480 inhabitants as of January 2016. Like Guadeloupe, it is an overseas region of France, consisting of a single overseas department. One of the Windward Islands, it is directly north of Saint Lucia, southeast of Greater Antilles, northwest of Barbados, and south of Dominica.

West Indies Island region in the Caribbean

The West Indies is a region of the North Atlantic Ocean in the Caribbean that includes the island countries and surrounding waters of three major archipelagos: the Greater Antilles, the Lesser Antilles and the Lucayan Archipelago.

Fort Desaix is a Vauban fort and one of four forts that protect Fort-de-France, the capital of Martinique. The fort was built from 1768 to 1772 and sits on a hill, Morne Garnier, overlooking what was then Fort Royal. Fort Desaix was built in response to the successful British attack on Fort Royal in 1762 and was intended to prevent any future attacker from using Morne Garnier to site cannon that could then bombard Fort Royal from above.

On his return to France, Coulomb was sent to Bouchain. However, he now began to write important works on applied mechanics and he presented his first work to the Académie des Sciences in Paris in 1773. In 1779 Coulomb was sent to Rochefort to collaborate with the Marquis de Montalembert in constructing a fort made entirely from wood near Île-d'Aix. During his period at Rochefort, Coulomb carried on his research into mechanics, in particular using the shipyards in Rochefort as laboratories for his experiments.

Bouchain Commune in Hauts-de-France, France

Bouchain is a commune in the Nord department in northern France.

Île-dAix Commune in Nouvelle-Aquitaine, France

Île-d'Aix is a commune in the Charente-Maritime department off the west coast of France. It occupies the territory of small island of Île d'Aix in the Atlantic. It is a popular place for tourist day-trips during the summer months.

Upon his return to France, with the rank of Captain, he was employed at La Rochelle, the Isle of Aix and Cherbourg. He discovered first an inverse relationship of the force between electric charges and the square of its distance and then the same relationship between magnetic poles. Later these relationships were named after him as Coulomb's law.

La Rochelle Prefecture and commune in Nouvelle-Aquitaine, France

La Rochelle is a city in western France and a seaport on the Bay of Biscay, a part of the Atlantic Ocean. It is the capital of the Charente-Maritime department.

Magnet material or object that produces a magnetic field

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.

In 1781, he was stationed at Paris. In 1787 with Tenon he visited the Royal Naval Hospital, Stonehouse and they were impressed by the revolutionary "pavilion" design and recommended it to the French government. On the outbreak of the Revolution in 1789, he resigned his appointment as intendant des eaux et fontaines and retired to a small estate which he possessed at Blois.

He was recalled to Paris for a time in order to take part in the new determination of weights and measures, which had been decreed by the Revolutionary government. He became one of the first members of the French National Institute and was appointed inspector of public instruction in 1802. His health was already very feeble and four years later he died in Paris.

Coulomb leaves a legacy as a pioneer in the field of geotechnical engineering for his contribution to retaining wall design. His name is one of the 72 names inscribed on the Eiffel Tower.


In 1784, his memoir Recherches théoriques et expérimentales sur la force de torsion et sur l'élasticité des fils de metal [3] (Theoretical research and experimentation on torsion and the elasticity of metal wire) appeared. This memoir contained the results of Coulomb's experiments on the torsional force for metal wires, specifically within a torsion balance. His general result is:

the moment of the torque is, for wires of the same metal, proportional to the torsional angle, the fourth power of the diameter and the inverse of the length of the wire.

Coulomb's torsion balance Bcoulomb.png
Coulomb's torsion balance

In 1785, Coulomb presented his first three reports on Electricity and Magnetism:

Il résulte donc de ces trois essais, que l'action répulsive que les deux balles électrifées de la même nature d'électricité exercent l'une sur l'autre, suit la raison inverse du carré des distances.

Translation: It follows therefore from these three tests, that the repulsive force that the two balls — [which were] electrified with the same kind of electricity — exert on each other, follows the inverse proportion of the square of the distance.

Four subsequent reports were published in the following years:

Coulomb explained the laws of attraction and repulsion between electric charges and magnetic poles, although he did not find any relationship between the two phenomena. He thought that the attraction and repulsion were due to different kinds of fluids.

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  1. "Coulomb". Random House Webster's Unabridged Dictionary .
  2. The "International Coulomb" was defined in modification of the International System of Electrical and Magnetic Units by the International Conference on Electrical Units and Standards (London, 1908) and adopted into the International System of Units in 1948. The name coulomb had already been used in earlier systems proposed by the British Science Association, hence the qualifier "international".
  3. Coulomb (1784) "Recherches théoriques et expérimentales sur la force de torsion et sur l'élasticité des fils de metal," Histoire de l’Académie Royale des Sciences, pages 229-269.
  4. Coulomb (1785a) "Premier mémoire sur l’électricité et le magnétisme," Histoire de l’Académie Royale des Sciences, pages 569-577.
  5. Coulomb (1785b) "Second mémoire sur l’électricité et le magnétisme," Histoire de l’Académie Royale des Sciences, pages 578-611.
  6. Coulomb (1785c) "Troisième mémoire sur l’électricité et le magnétisme," Histoire de l’Académie Royale des Sciences, pages 612-638.
  7. Coulomb (1786) "Quatrième mémoire sur l’électricité," Histoire de l’Académie Royale des Sciences, pages 67-77.
  8. Coulomb (1787) "Cinquième mémoire sur l’électricité," Histoire de l’Académie Royale des Sciences, pages 421-467.
  9. Coulomb (1788) "Sixième mémoire sur l’électricité," Histoire de l’Académie Royale des Sciences, pages 617-705.
  10. Coulomb (1789) "Septième mémoire sur l’électricité et le magnétisme," Histoire de l’Académie Royale des Sciences, pages 455-505.