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Equipment provided for the session

Set-up used to discharge the charge on the sphere

Measuring the charge on the sphere

Discharging the sphere

Discharging the sphere

Testing Coulomb's Law

In this session you will have:

Understood how electrostatic charges are measured


Confirmed the inverse square law for the electrostatic force


Determined the magnitude of the electrostatic force


The electrostatic force is one of the four fundamental forces of nature and was first systematically studied by Charles Coulomb in the 1780s. Using very careful measurements of the forces between charged spheres he deduced Coulomb's law:


The magnitude of the electrostatic force between two point electric charges is directly proportional to the product of the magnitudes of each charge and inversely proportional to the square of the distance between the charges.

Charles Coulomb
French military engineer and physicist, discoverer of Coulomb's Law

In this experiment you will confirm the inverse square dependence of the electrostatic force by measuring the force between a charged sphere and its image induced in a metal plate. You will also determine the strength of the force - one of the fundamental constants of nature.

Other Resources


The script for this experiment can be found in the lab script book or on DUO.