In 1909, Robert Millikan and Harvey Fletcher conducted the oil drop experiment to determine the charge of an electron. They suspended tiny charged droplets of oil between two metal electrodes by balancing downward gravitational force with upward drag and electric forces. The density of the oil was known, so Millikan and Fletcher could determine the droplets’ masses from their observed radii (since from the radii they could calculate the volume and thus, the mass). Using the known electric field and the values of gravity and mass, Millikan and Fletcher determined the charge on oil droplets in mechanical equilibrium. By repeating the experiment, they confirmed that the charges were all multiples of some fundamental value.

This Millikan's apparatus permits the atomising of a latex solution into small spheres and the rubber hose induces a static charge upon them. They are introduced between charged plates in the form of a cell. As the voltage between these cell plates is reversed, the particles are attracted to one plate or the other. Their movement is viewed through a small telescope with a graticule. Power sources are required to be connected. Knowing the potential on the cell plates and plotting the velocities of the spheres permits the calculation of the charge on a single electron.

Instructions and guide included.  Made in Australia.