AD 1785
Charles Augustin de Coulomb
Measures electrostatic force
Charles Augustin de Coulomb (1736-1806),invented the torsin balance which could measure
electrostatic force. Inside the balance are two pith balls. One is mounted and unmovable the other
can roll around. When the two pith balls are enegized by an electrostatic charge the moveable one will be
roll away from the stationary one if both receive the same type of charge (positive or negative). It will
roll towards the stationary pith ball if each receives a different charge. The distance it rolls is used to
measure the electrostatic force.
Coulumb discovered that the forceof repulsion was inversely proportional to the square of the distance between
the cneters of the two spheres. This is known as the Law of Inverse Squares: f = k(Q1 x Q2) / d(squared)
where f is force, Q1 and Q2 are the charges, d is the distance, and k is a constant.
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