Construction et usage d'une balance électrique, fondée sur la propriété qu'ont les fils de métal, d'avoir une force de réaction de torsion proportionnelle à l'angle de torsion
Author(s)
Coulomb, Charles-Augustin (author), Louis Bucciarelli (translator)![Thumbnail](/bitstream/handle/1721.1/143551/Coulomb_El_1785.pdf.jpg?sequence=6&isAllowed=y)
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Alternative title
Construction and use of an electric balance founded on the the property of metal wires namely the proportionality of the torque to the angle of twist.
Metadata
Show full item recordAbstract
In a memoir presented to the Academy, in 1784, I have determined from experiments the laws governing the torsional resistance of a filament of metal and I have found that this force is proportional to the angle of torsion, to the fourth power of the diameter of the suspended filament and inversely proportional to its length - all multiplied by a constant coefficient which depends on the nature of the metal and is easily determined by experiment.
I have shown in the same Memoir that by means of this force of torsion, it was possible to precisely measure extremely small forces as, for example, one ten thousandths of a grain1. In the same Memoir I described a first application of this theory, seeking to evaluate the constant force attributed to adhesion in the formula for the surface friction of a solid body moving through a fluid.
Today, I set before the eyes of the Academy, an electric balance constructed according to the same principles. It measures with the greatest precision the state and the electric force of a body, however weak the degree of electricity.
Description
This translation of Coulomb's memoir on electric charge was made for a course taught by Louis Bucciarelli and Jed Buchwald at MIT (circa 2000) in which students attempted to replicate historic experiments using only the devices and materials available at the time of the original tests. The "electric balance" used by Coulomb to determine that the repulsive force varied inversely as the square of the distance was built in accord with the results of experiments on the torsion of metal wires reported in a prior memoir presented to the Academy in 1784. A translation of the latter has also been posted to this collection.
Date issued
2022-06-24Series/Report no.
Histoire de l'Académie [royale] des sciences avec les mémoires de mathématiques et de physique,;"Mémoires" [1785], 1788, p. 569-577.
Keywords
electric charge, electrical balance