Conversion of Units and Conversion Factors

The metric system became preferred by scientists of the nineteenth century, partly
because it was intended to be an international system of measurement, partly because the
units of measurement were theoretically supposed to be independently reproducible, and
partly because of the simplicity of its decimal nature. Problems in the specification of the
units for electricity and magnetism led to numerous international conferences to rectify
inconsistencies and culminated in 1960 in the eleventh General Conference on Weights
and Measures adopting the SI (Systeme International) system I of units. As of this date
the United States is the last large country not employing or engaged in transforming to
some form of the SI units. Tables 1.1 and 1.2 show the most common systems of units
used by engineers in the last few decades. Note that the SI, the cgs, the fps (English
absolute), and the British engineering systems all have three basically defined units and
that the fourth unit is derived from these three defined units .