TABLE A-3 DERIVED SI UNITS

Basic Electrical Theory METRIC SYSTEM AND POWERS OF TEN TABLE A-3 DERIVED SI UNITS Quantity Derived Symbol Unit Energy joule J Force newton N Power watt W Electric charge coulomb C Electric potential volt V Electric resistance ohm W Electric conductance mho Electric capacitance farad F Electric inductance henry H Frequency hertz Hz Magnetic flux weber Wb Magnetic flux density tesla T Metric Prefixes When working with basic electrical measurement units, sometimes the values are too large or too small to express conveniently. For convenience, add metric prefixes (Table A-4) to the basic unit. For example, if we have a resistor that is 1,000,000 ohms (W), we can add the prefix kilo, or its designated symbol K, and express the value as 1,000 KW, or the metric prefix mega (symbol M) and express the value as 1 MW. In the case of capacitance or current, we may have a very small value such as 0.002 amperes (symbol A) or 0.000005 farads (symbol F). These values can be expressed by adding the prefix milli (symbol m) and expressing the current as 2 milli amperes or 2 mA, or adding the prefix micro (symbol µ) and expressing the capacitance as 5 micro farads, or 5 µF. Rev. 0 Page A-3 ES-01