Charles-Augustin de Coulomb, a French physicist, used a very clever and precise method to measure the force between electric charges. He employed a device known as a torsion balance. Here's a breakdown of how it worked:

The Torsion Balance:

1. Setup: The torsion balance consisted of a lightweight, horizontal rod suspended by a thin, vertical wire. A small charged sphere was attached to one end of the rod, and another charged sphere (fixed in position) was brought near the first sphere.

2. Twisting and Measuring: When the two charged spheres interacted, the repulsive or attractive force between them would cause the rod to twist. The amount of twist was proportional to the force between the charges.

3. Calibration and Measurement: The wire had a known torsional constant (how much it twisted for a given force). Coulomb carefully calibrated the balance by applying known forces and measuring the resulting twists. This allowed him to relate the amount of twist to the actual force between the charges.

4. Varying the Charges and Distance: Coulomb could vary the charges on the spheres and the distance between them. By observing how the twist of the rod changed, he was able to establish a relationship between the force, the magnitude of the charges, and the distance separating them.

Coulomb's Law:

Through his meticulous experiments, Coulomb discovered that the force between two charges is:

* Directly proportional to the product of the charges: The larger the charges, the stronger the force.

* Inversely proportional to the square of the distance between them: The closer the charges, the stronger the force.

This relationship is now known as Coulomb's Law.

Significance:

Coulomb's experiments were groundbreaking because they provided the first quantitative understanding of the fundamental force between electric charges. His work paved the way for the development of electromagnetism and continues to be foundational in our understanding of electricity and magnetism.