1), we
see that for q1 = q2 = 1 C, r = 1 m
F = 9 × 109 N
That is, 1 C is the charge that when placed at a distance
of 1 m from another charge of the same magnitude in vacuum
experiences an electrical force of repulsion of magnitude
*
A torsion balance is a sensitive device to measure force It was also used later
by Cavendish to measure the very feeble gravitational force between two objects,
to verify Newton’s Law of Gravitation *
Implicit in this is the assumption of additivity of charges and conservation:
two charges (q/2 each) add up to make a total charge q Charles Augustin de
Coulomb (1736 – 1806)
Coulomb, a French
physicist, began his
career as a military
engineer in the West
Indies