METRIC SYSTEM AND POWERS OF TEN
Basic Electrical Theory
TABLE A-2
SUPPLEMENTARY SI UNITS
Quantity
Unit
Symbol
Plane angle
radian
rad
Socid angle
steradian
Sr
These base and supplemental units are used to derive other units. Most of the units of measure
used in electricity are derived units. These units are shown on Table A-3. Some of these are
derived from the base units, and some are derived from other derived units, or a combination of
both. For example, the unit of current is the ampere, which is derived from the base units of
second and coulomb. The derivation of these units is beyond the scope of this text. However,
units commonly used in the study and use of electricity and their relationship to other units of
measure are discussed in Chapter 3, Units of Electrical Measurement.
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