23rd IMEKO TC 4 International Symposium and the 5th Chinese Conference on Electromagnetic Metrology Technical (IMEKO TC4 2019)

226 / 2019-06-29 23:32:20

Review determination of the elementary charge e

metrology; International System of Unit, SI; CGSE; CGSM; MKSA; Millikan’s oil-drop experiment; elementary charge; Planck constant; fine structure constant; vacuum permeability

Plenary track > Calibration, Metrology and Standards

Reviews the history of measuring electric charge and electromagnetic unit system. Interpret signification that the elementary charge become member of International System of Unit. The Coulomb’s law and Ampere’s law were two bridges to link mechanics and electromagnetism. Along with these two formulae, the electrostatic and the electromagnetic absolute unit systems were respectively grown up. The comer of the practical unit systems brought electromagnetism to have its own individual unit system, and chose current as basic quantity and fixed vacuum permeability, aimed at electromagnetic power to be equivalent mechanic power. The Millikan’s oil-drop is the only experiment to measure elementary charge value. Because low accuracy, the metrological standard system of electric charge have not been appeared. To define the value of elementary charge did not depend on the two constants of Josephson’s KJ and von Klitzing’s RH, but came from the formula of fine structure constant, after the value of Planck constant was fixed. The role of vacuum permeability changed thoroughly after the elementary charge fixed, it had become a balance between two unit systems of electromagnetism and mechanics in the Ampere’s law.