Charles de Coulomb

Claimed by Alanna Carnevale

Charles-Augustin de Coulomb was a French physicist most well known for the discovery of Coulomb's Law and his work with friction. The SI unit for electric charge known as the coulomb was named after him.

Personal Life

Coulomb was born in Angoulême, France, on June 14, 1736 to Henry Coulomb and Catherine Bajet. Both his parents were rather wealthy, as his father was a lawyer, and his mother came from a well-established family. After being raised in Angoulême, Coulomb and his family moved to Paris where he would enter college.

When Henry Coulomb made poor financial choices, lost all of his money, and moved to Montpellier, Charles de Coulomb had to make the decision of whether to move with him or stay in Paris with his mother. Coulomb decided to live with his father after a disagreement with mother about his future career. In March 1757, he joined the Society of Sciences in Montpellier to whom which he would read many papers on mathematics as well as astronomy. Around February 1760, when Coulomb was entering the École du Génie at Mézières he made many significant friends including Bossut and Borda.

During the beginning of the French Revolution, Coulomb was in intense scientific study. He was expelled from the government as many French aristocrats were at the time, and he retired from the Corps du Genie. Coulomb married the mother of his two sons in 1802, Louise Francoise LeProust Desormeaux. Due to work in the West Indies, Coulomb suffered from sicknesses that caused him to be in poor health for the rest of his life. He fell ill with a fever in 1796 and passed away on August 23, 1806 in Paris at the age of 70.

University Education and Career

Charles de Coulomb started his college education at Collège Mazarin in Paris where he learned language, literature, philosophy, mathematics, astronomy, chemistry, and botany. He was most interested in mathematics and astronomy. After moving to Montpellier Coulomb realized he wanted to enter the École du Génie at Mézières but first needed to be tutored so that he could pass the entrance exams. Coulomb studied Camus’s Cours de mathématiques and passed the exams. He graduaded from École du Génie at Mézières in November 1761.

As both a trained engineer and a Corps du Génie lieutenant, Coulomb would be take on a variety of career positions. He went from Brest in February of 1764 to Martinique in the West Indies where he would contribute to making the island safer by building a fort named Fort Bourbon. Coulomb also spent time in Bouchain as well as Cherbourg where Coulomb submitted a memoir to the appointed comptroller general Robert-Jacques Turgot that regarded possible reformations. Coulomb’s political views were present in this memoir and he included how he wanted the state and the individual to be equal. Coulomb also was stationed in Rochefort in 1779 where he would construct a wood fort near Ile d'Aix.

Besides all of this work, Coulomb also participated in fields such as education and hospital reformations. He became in charge of watching over royal fountains and a large part of the Paris water supply in 1784. Coulomb spent his last years working with education as inspector general of pubic instruction.

Scientific Contribution

Coulomb wrote many important works throughout his life. One of these entailed a combination of mathematics and physics, which would determine the influence of friction and cohesion in statics problems. It is notable that Coulomb used variations of calculus to solve engineering problems.

Coulomb wrote a famous memoir on the magnetic compass, which contained his first work on the torsion balance. His use of torsion balance would help many physicists with their works in years to come.

Coulomb also used shipyards in Rochefort as laboratories to come up with his major work on friction titled ‘’Théorie des machines simples’’. This work, consisting of both static and dynamic friction of sliding surfaces and friction in bending of cords and in rolling, caused him to win the Grand Prix in 1781 from the Académie des Sciences.

Coulomb gave twenty-five memoirs to the Académie des Sciences between 1781 and 1806 and contributed to work with 310 committees.

Coulomb’s Law

Coloumb used a torsion balance to examine repulsion and attraction forces of charged particles. This torsion balance he used includes an insulating rod with a metal-coated ball attached to an end suspended from the middle of it by a silk thread. After charging the ball with static electricity, a second charged ball would be brought near it. The two balls repelled one another. Through much analysis, he discovered 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 the charges. The force is along the straight path between them, and if the charge of the two particles have the same sign then the force is repulsive while if they have different signs the force is attractive.

[math]\displaystyle{ \ |F|=\frac{1}{4 \pi \epsilon_0 } \frac{|q_1q_2|}{r^2},\text{where } \frac{1}{4 \pi \epsilon_0 } \text{is approximately } 9*10^{9}, \text{q1 and q2 are the charges of the particles, and r is the magnitude of the distance between the two.} }[/math]

The first part of this equation, [math]\displaystyle{ \ \frac{1}{4 \pi \epsilon_0 } }[/math] , often denoted as [math]\displaystyle{ \ k_e }[/math] is Coulomb's constant which is a proportionality factor.

Interesting Facts

Coulomb leaves a legacy as a pioneer in geotechnical engineering for his contribution to retaining wall design.

Charles de Coulomb's name is one of the 72 names inscribed on the Eiffel Tower.

Coulomb explained the laws of attraction and repulsion between magnetic poles and electric charges, but he did not find any relationship between the two. He believed that the attraction and repulsion were brought on by different kinds of fluids.

Coulomb worked strenuously on friction of machinery, windmills, and the elasticity of metal and silk.