nauka: Elementary charge

Evidence: 91 • authority: 72

The elementary charge, usually denoted by e, is the magnitude of the charge on an electron and a fundamental physical constant defined to be exactly e = 1.602176634×10−19 C. The elementary charge is a measure of the coupling strength of the electromagnetic force and one of the seven defining constants of the International System of Units (SI). Before being set to a fixed value as part of the 2019 revision of the SI, the elementary charge was viewed as a quantity to be determined experimentally. Robert A. Millikan and Harvey Fletcher's oil drop experiment first directly measured the magnitude of the elementary charge in 1909, differing from the modern accepted value by just 0.6%. Under assum…

Evidence: 74 • authority: 72

The oil drop experiment was performed by Robert A. Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron). The experiment took place in the Ryerson Physical Laboratory at the University of Chicago. Millikan received the Nobel Prize in Physics in 1923. The experiment observed tiny electrically charged droplets of oil located between two parallel metal surfaces, forming the plates of a capacitor. The plates were oriented horizontally, with one plate above the other. A mist of atomized oil drops was introduced through a small hole in the top plate; some would be ionized naturally. First, with zero applied electric field, the velocity of a fa…

Evidence: 36 • authority: 88

The Oil Drop Experiment: How Did Millikan Decide What Was an Appropriate Drop?. The oil drop experiment is considered an important contribution to the understanding of modern physics and chemistry. The objective of this investigation is to study and contrast the views and understanding with respect to the experiment of physicists or philosophers of science with those of authors of physics or chemistry textbooks and laboratory manuals. Results obtained show that physicists and philosophers of science do understand that the experiment is difficult to perform even today, primarily because of the difficulty associated with the selection of the appropriate drops and that consensus was achieved i…

Evidence: — • authority: 90

Millikan, the First Physicist to See the Electron. In 1923, the American physicist Robert Andrews Millikan (1868-1953) was awarded the Nobel Prize for Physics “for his work on the elementary charge of electricity and on the photoelectric effect”. In his Nobel Lecture “The Electron and the Light-Quant from the Experimental Point of View” he referred to the experiment that had enabled him determine the charge of the electron, leaving his audience convinced that he had seen electrons: “He who has seen that experiment, and hundreds of investigators have observed it, has literally seen the electron”. Quite often we physicists say that we see those things on which we are working, no matter how sm…

Evidence: — • authority: 90

Millikan's experiment revisited. Description of the Millikan experiment using the mass-charge force. It may be that Millikan’s classic oil drop experiment is not driven by the force of gravity, which acts in opposition to the electric force, but that it is rather the mass-charge force that pulls the charged droplets of oil down to earth. Accordingly, the force of gravity would\nhave only an extremely small effect in opposition to the electric force, and the mass-charge force would act as the major opposing force to the electric force. Thereby the mass charge force is the force between the earth’s mass and the charge of the oil droplets. This force is believed to act in opposition to the ele…

Evidence: — • authority: 90

Robert Millikan and His Role in the Birth of Modern Radio Tubes. The article focuses on the work of Harold Wilson, Robert Millikan and his students, in particular, Louis Begeman and Harvey Fletcher on determining the magnitude of an elementary electric charge. Attention is drawn to the priority of authorship in the publications of R. Millikan and H. Fletcher based on the results of joint research. A controversy was noted around the results of Millikan’s experiments to determine the electric charge of an electron. The situation with R. Millikan’s recommendation of his student Harold de Forest Arnold to the WECo research group for the development of a telephone electronic repeater is describe…

Evidence: — • authority: 90

Effects of Brownian Motion on the Millikan Oil Drop Experiment. Brownian motion has a significant effect on small particles suspended in a fluid. Since the Millikan oil drop experiment involves measuring the rise and fall velocities of very small oil drops suspended in air, it stands to reason that the motion of these drops will be affected by collisions with particles of air. The result of this is that the measured rise and fall velocities of each drop will not be the same as if these drops were suspended in vacuum. The size of the effect of Brownian motion is related to the mass and the radius of the oil drop, and is also related to the temperature of the surrounding fluid. In our experim…