|Lam Chun-hung (Translation by Wong Wing-hung & Janny Leung)|
Coulomb returned to France and joined a conference called by the French Academy of Sciences in 1776. He solved some problems in navigation facilities and also carried out an in-depth study in magnetism in the conference. Since he had designed a new compass and had made many contributions to the theories of machines, he was elected as a member of the French Academy of Sciences in 1782.
Coulomb invented a torsion balance in 1777, which was later called Coulomb balance. This balance can be used to measure weak forces. From 1785 to 1789, he published seven articles on electricity and magnetism. He also used Coulomb balance to measure the electric force between two point charges. He confirmed that this force is proportional to the product of the two charges but inversely proportional to the square of the distance between them. This law, Coulomb's Law, is also known as the inverse-square law.
Apart from scientific research, Coulomb also participated in social activities. He held an important position in the Education Department of France and was the Chancellor of Water Works and Resources Department. However, some senior officers hated him and thus all his social activities were stopped. French Revolution began in 1789. Coulomb then became a recluse for several years and concentrated on scientific research.
Coulomb's series of publications enriched the computational methods in electricity and magnetism, and extended Newtonian principles of mechanics to the context of electricity and magnetism. His torsion balance is very useful in precise measurements and other aspects of experimental physics. After Napoleon had reigned, he resumed all Coulomb's duties. Coulomb assumed these duties until he died in Paris in 1806.