Metric Prefixes in Quantities and Units

Quantities and Units

• The metric prefix mega has replaced 10^6.

Metric Prefixes

• Metric prefixes represent powers of ten in engineering notation.
• Table 3 lists metric prefixes with their symbols, powers of ten, and values.

Examples of Conversion

• 50,000 V = 50 * 10^3 V = 50 kV
• 25,000,000 Æ = 25 * 10^6 Æ = 25 MÆ
• 0.000036 A = 36 * 10^-6 A = 36 µA

Converting between Units with Metric Prefixes

• To convert from a larger unit to a smaller unit, move the decimal point to the right.
• To convert from a smaller unit to a larger unit, move the decimal point to the left.
• Determine the number of places to move the decimal point by finding the difference in the powers of ten of the units being converted.

Examples of Metric Unit Conversions

• 0.15 milliampere (0.15 mA) = 0.15 * 10^-3 A = 150 * 10^-6 A = 150 µA
• 4500 microvolts (4500 mV) = 4500 * 10^-6 V = 4.5 * 10^-3 V = 4.5 mV
• 5000 nanoamperes (5000 nA) = 5000 * 10^-9 A = 5 * 10^-6 A = 5 µA
• 47,000 picofarads (47,000 pF) = 47,000 * 10^-12 F = 0.047 * 10^-6 F = 0.047 µF
• 0.00022 microfarad (0.00022 mF) = 0.00022 * 10^-6 F = 220 * 10^-12 F = 220 pF
• 1800 kilohms (1800 kÆ) = 1800 * 10^3 Æ = 1.8 * 10^6 Æ = 1.8 MÆ

History of Metric Units

• In 1954, the basic SI units (meter, kilogram, second, ampere, kelvin, and candela) were adopted by international agreement.
• The mks (meter-kilogram-second) units are used for derived quantities and are the preferred units for nearly all scientific and engineering work.
• The cgs system, based on the centimeter, gram, and second, is an older metric system that is still in use in some areas.