The Permeability of Vacuum and the Revised International System of Units

Published: December 29, 2017


Ronald B. Goldfarb


The International System of Units (SI) is expected to be revised such that all seven base units, including the kilogram, will be defined in terms of fixed numerical values of seven defining constants. The revised SI will include a redefinition of the ampere. One consequence is that the permeability of vacuum will not have a fixed numerical value but will become, in principle, a measurable quantity. The constitutive relation among magnetic flux density, magnetic field strength, and magnetization will not change. However, its expression in the centimeter-gram-second system of electromagnetic units (EMU), where the permeability of vacuum is unity, will no longer be ontologically equivalent, and quantities will not be exactly convertible to the SI. Already contrary to international convention, the still common EMU system will become obsolete.
Citation: IEEE Magnetics Letters
Volume: 8
Pub Type: Journals


Electromagnetism, permeability of vacuum, permeability of free space, magnetic constant, magnetic units, International System of Units, electromagnetic system of units
Created December 29, 2017, Updated January 08, 2018