Determining the value of the finestructure constant from a current balance: Getting acquainted with some upcoming changes to the SI
Abstract
The revised International System of Units (SI), expected to be approved late in 2018, has implications for physics pedagogy. The ampere definition, which dates from 1948, will be replaced by a definition that fixes the numerical value of the elementary charge e in coulombs. The kilogram definition, which dates from 1889, will be replaced by a definition that fixes the numerical value of the Planck constant h in joule seconds. Existing SI equations will be completely unaffected. However, there will be a largely negligible, but nevertheless necessary, change to published numerical factors relating SI electrical units to their corresponding units in the Gaussian and other CGS systems of units. The implications of the revised SI for electrical metrology are neatly illustrated by considering the interpretation of results obtained from a current balance in the present SI and in the revised SI.
 Publication:

American Journal of Physics
 Pub Date:
 May 2017
 DOI:
 10.1119/1.4976701
 arXiv:
 arXiv:1610.02910
 Bibcode:
 2017AmJPh..85..364D
 Keywords:

 Physics  Classical Physics
 EPrint:
 The updated version (version 3) has been published in the American Journal of Physics after reformatting by the journal