![]() When there is no electric field present, the drop under observation falls slowly, subject to the downward pull of gravity and the upward force due to the viscous resistance of the air to the motion of the oil drop. The oil drops in this experiment are subject to three different forces: viscous, gravitational and electrical. A potential difference is applied across the plates (one plate becomes positivelycharged and the other plate becomes negatively charged) producing an electric field. The oil drops became electrically charged through friction with the nozzle as they were sprayed. A hole in the upper plate facilitates entry of oil drops from the spray chamber above. The apparatus used consists of a chamber which has two metal plates that are seperated by a ring of insulating material. A fine mist of oil droplets are sprayed into a chamber above the plates. Previous to the oil drop experiment they knew charge was held in a sub-atomic particle called an electron but in this experiment Milikan measured the elementary electric charge to an unprecedented accuracy and thereby confirmed the quantum nature of charge. The experiment has now become a staple in physics education for students. This breakthrough in Physics became known as the oil drop experiment and Robert Millikan won the Nobel Prize in Physics for it in 1923. In 1909, Robert Millikan and Harvey Fletcher conducted an experiment to determine the charge of an electron. Centre for Continuing Professional Development.Sustainable Development Goals in UCC Research.
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