Alfred-Marie Liénard (2 April 1869 in

Amiens Amiens (English: or ; ; pcd, Anmien, or ) is a city and commune in northern France, located north of Paris and south-west of Lille. It is the capital of the Somme department in the region of Hauts-de-France. In 2021, the population of ...

– 29 April 1958 in

Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. S ...

), was a French

physicist 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 caus ...

and

engineer Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the l ...

. He is most well known for his derivation of the

Liénard–Wiechert potential The Liénard–Wiechert potentials describe the classical electromagnetic effect of a moving electric point charge in terms of a vector potential and a scalar potential in the Lorenz gauge. Stemming directly from Maxwell's equations, these descr ...

s. From 1887 to 1889 Liénard was a student at the

École Polytechnique École may refer to: * an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing in région Île-de-France * École, Savoi ...

and from 1889 to 1892 at the

École des mines de Paris Mines Paris - PSL, officially École nationale supérieure des mines de Paris (until May 2022 Mines ParisTech, also known as École des mines de Paris, ENSMP, Mines de Paris, les Mines, or Paris School of Mines), is a French grande école and a c ...

. From 1892 to 1895 he was a

mining engineer Mining in the engineering discipline is the extraction of minerals from underneath, open pit, above or on the ground. Mining engineering is associated with many other disciplines, such as mineral processing, exploration, excavation, geology, and ...

Valencia Valencia ( va, València) is the capital of the Autonomous communities of Spain, autonomous community of Valencian Community, Valencia and the Municipalities of Spain, third-most populated municipality in Spain, with 791,413 inhabitants. It is ...

Marseille Marseille ( , , ; also spelled in English as Marseilles; oc, Marselha ) is the prefecture of the French department of Bouches-du-Rhône and capital of the Provence-Alpes-Côte d'Azur region. Situated in the camargue region of southern Franc ...

, and

Angers Angers (, , ) is a city in western France, about southwest of Paris. It is the prefecture of the Maine-et-Loire department and was the capital of the province of Anjou until the French Revolution. The inhabitants of both the city and the prov ...

. From 1895 to 1908 he was professor at the École des Mines de Saint-Étienne and from 1908 to 1911 he was professor of electrical engineering at the École des Mines de Paris. In

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

he served in the

French Army The French Army, officially known as the Land Army (french: Armée de Terre, ), is the land-based and largest component of the French Armed Forces. It is responsible to the Government of France, along with the other components of the Armed For ...

. Liénard worked in the fields of

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...

magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...

, and

mechanics Mechanics (from Ancient Greek: μηχανική, ''mēkhanikḗ'', "of machines") is the area of mathematics and physics concerned with the relationships between force, matter, and motion among physical objects. Forces applied to objects r ...

. In 1898 (and two years after him

Emil Wiechert Emil Johann Wiechert (26 December 1861 – 19 March 1928) was a German physicist and geophysicist who made many contributions to both fields, including presenting the first verifiable model of a layered structure of the Earth and being among the ...

), he derived what is now called the

s. He also investigated problems related to the

elasticity Elasticity often refers to: *Elasticity (physics), continuum mechanics of bodies that deform reversibly under stress Elasticity may also refer to: Information technology * Elasticity (data store), the flexibility of the data model and the cl ...

and strength of materials, and wrote papers on

thermodynamics Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of the ...

and

hydrodynamics In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) and ...

. Along with M. H. Chipart, Liénard developed the

Liénard–Chipart criterion In control system theory, the Liénard–Chipart criterion is a stability criterion modified from the Routh–Hurwitz stability criterion, proposed by A. Liénard and M. H. Chipart. This criterion has a computational advantage over the Routh–H ...

for determining the stability of a continuous-time system of equations. Liénard was a commander of the

Légion d'honneur The National Order of the Legion of Honour (french: Ordre national de la Légion d'honneur), formerly the Royal Order of the Legion of Honour ('), is the highest French order of merit, both military and civil. Established in 1802 by Napoleon ...

. He was also vice-president of the Société Française des Électriciens and he was president of the

Société Mathématique de France Lactalis is a French multinational dairy products corporation, owned by the Besnier family and based in Laval, Mayenne, France. The company's former name was Besnier SA. Lactalis is the largest dairy products group in the world, and is the sec ...

References

External links

*Annales.org
Alfred-Marie Liénard
{{DEFAULTSORT:Lienard, Alfred Marie French electrical engineers École Polytechnique alumni Mines Paris - PSL alumni Corps des mines 1869 births 1958 deaths French physicists French engineers

See also

References

External links