The oil drop experiment was first performed by Robert A. Millikan and Harvey Fletcher to measure the elementary electric charge (the charge of the electron).
This consists of a compact apparatus for demonstrating the discrete nature (quantisation) of electric charge and for determining the elementary charge of an electron.
The experiment entails observing tiny charged droplets of oil between two horizontal metal electrodes. First, with zero applied electric field, the droplets are allowed to fall between the plates and the terminal velocity of a droplet is measured.
Then an adjustable voltage is applied between the plates to induce an electric field, until the drops are suspended in mechanical equilibrium indicating that the electrical force and the gravitational force are balanced.
The experiment is set up on a tripod and consists of a plate capacitor under a metal cover, measuring microscope, lighting apparatus and an oil atomiser.
A plastic bottle containing oil is included in the kit.
The power supply for this apparatus is available with us and can be bought separately.