Abstract The history of measuring electric charge and electromagnetic unit system was reviewed, and the signification that the elementary charge become member of International System of Unit was interpreted. The Coulombs law and Amperes 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 Millikans oil-drop is the only experiment to measure elementary charge value. Because of the 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 Josephsons KJ and von Klitzings RK, 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 Amperes law.
［1］宋明顺,方兴华,马爱文,等. 论新国际单位制(SI)的“秒制”特征及其未来发展［J］. 计量学报,2019, 40(4): 541-548.
Song M S, Fang X H, Ma A W, et al. The Characteristics of the New SI Base on “second system” and its Future Development［J］. Acta Metrologica Sinica, 2019, 40(4): 541-548.
［2］Stopes Roe H V. MKSA Giorgi and SI ［J］. Nature, 1969, 222 (3):500-502.
［3］Frezza F, Maddio S, Pelosi G, et al. The life and work of Giovanni Giorgi: The Rationalization of the International System of Units ［J］. IEEE Antennas & Propagation Magazine, 2015, 57(6):152-166.
［4］Franklin A. Millikans Oil-Drop Experiments ［J］. The Chemical Education, 1977, 2(1):1-14.
［5］Li Y Z, Zhang L W, Shan G Q, et al. Measurement reduction method for the Millikan oil-drop experiment ［J］. European Journal of Physics, 2015, 36(5):055022.
［6］Petley B W. The Josephson Effects ［J］. Contemporary Physics, 2009, 50(1): 71-90.
［7］Stein F, Gerster T, Behr R, et al. Accuracy verification of single-electron pumps with 0.2 ppm uncertainty ［C］//IEEE.2016 Conference on Precision Electromagnetic Measurements .Ottawa, Canada,2016.(DOI: 10.1109/CPEM.2016.7540620)
［8］Piquemal F, Bounouh A, Devoille L, et al. Fundamental electrical standards and the quantum metrological triangle［J］.Academie des Sciences. Comptes Rendus, Physique, 2004, 5(8):857-879.
［9］张钟华. 电磁计量的量子基准及量子三角形［J］. 前沿科学, 2008,2(7):4-9.
Zhang Z H. The quantum standards in electromagnetic and the quantum triangle ［J］. Frontier Science, 2008,2(7):4-9.
［10］Nath B . The fine structure constant ［J］. Resonance, 2015, 20(5):383-388.
［11］Kragh H. The fine-structure constant before quantum mechanics ［J］. European Journal of Physics, 2003, 24(2): 169-173.
［12］Kinoshita T. Improvement of the fine-structure constant obtained from the electron g-2 ［J］. IEEE transaction on instrumentation and measurement, 2001,50(2):568-572.
［13］Aoyama T, Hayakawa M, Kinoshita T, et al. Tenth-order QED contribution to the electron g-2 and improved value of the fine structure constant ［J］. Physical Review Letters, 2012,109(11):111807.
［14］GoldfarbR B. Persistence of Electromagnetic Units in Magnetism ［C］//CPEM. 2018 Conference on Precision Electromagnetic Measurement. Xian, China, 2018.
［15］ Fletcher N. The role of the magnetic constant μ0 in the redefinition of the SI ［C］ //CPEM. 2018 Conference on Precision Electromagnetic Measurement. Xian, China, 2018.
