Electrical Power Systems Technology

Power Measurement Fundamentals 9

4. Unit of electrical charge: COULOMB (C)—the amount of electrical
   charge transferred in 1 second by a current of 1 ampere; 1 coulomb =
   1 ampere per second.

CONVERSION OF SI UNITS

Sometimes it is necessary to make conversions of SI units, so that

very large or very small numerals may be avoided. For this reason, deci-

mal multiples and submultiples of the base units have been developed, by

using standard prefixes. These standard prefixes are shown in Table 1-3.

Multiples and submultiples of SI units are produced by adding prefixes to

the base unit. Simply multiply the value of the unit by the factors listed in

Table 1-3. For example:

1 kilowatt = 1000 watts

1 microampere = 10–6 ampere

1 megohm= 1,000,000 ohms

Table 1-3. SI Standard Prefixes

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Prefix Symbol Factor by Which the Unit is Multiplied

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exa E 1,000,000,000,000,000,000 = 10^18

peta P 1,000,000,000,000,000 = 10^15

tera T 1,000,000,000,000 = 10^12

giga G 1,000,000,000 = 10^9

mega M 1,000,000 = 10^6

kilo k 1,000 = 10^3

hecto h 100 = 10^2

deka da 10 = 10^1

deci d 0.1 = 10–

centi c 0.01 = 10–

milli m 0.001 = 10–

micro μ 0.000001 = 10–

nano n 0.000000001 = 10–

pico P 0.000000000001 = 10–

femto f 0.000000000000001 = 10–

atto a 0.000000000000000001 = 10–

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