Millikan’s oil-drop experiment established that electric charge is quantized.
Millikens Oil Drop Experiment
In 1909, Robert A. Millikan and Harvey Fletcher conducted the Millikens Oil Drop Experiment to determine the charge of an electron. Milliken created an electric field by allowing charged tiny oil droplets to move through a hole. The charge over an oil droplet was determined by varying the strength of the electric field, which always came as an integral value of ‘e.’
Conclusion of Millikens Oil Drop Experiment
The charge over any oil droplet is always an integral value of e (1.6 x 10-19). Hence, the conclusion of Millikens Oil Drop Experiment is that the charge is said to be quantized, i.e. the charge on any particle will always be an integral multiple of e.