AAT ICAS 2019 ✧ overview of International System of Units (SI)
- overview of International System of Units (SI)
- table 2019.1 ✧ SI base units, defining constants, and corresponding units
- table 2019.2 ✧ some derived SI units
- table 2019.3 ✧ some derived SI units with special names
- table 2019.4 ✧ some other units designated for use with SI
- table 2019.5 ✧ prefixes for binary multiples
- table 2019.6 ✧ comparison of SI and binary prefixes
overview of International System of Units (SI)
this document provides a general overview of the International System of Units and is not intended as a specification or reference of SI. additional information about SI is also noted in the AAT ICAS 2076 metrication resources module.
SI (International System of Units) is defined in the SI concise summary and the SI brochure that is available from bipm.org. effective on World Metrology Day 2019 (AD 2019 May 20 Monday), the SI units are now exclusively defined in terms of physical constants of atomic and quantum phenomena. please also refer to the following Metrologia article.
table 2019.1 ✧ SI base units, defining constants, and corresponding units
quantity | base unit (symbol) | defining constant (symbol) | numerical value | (corresponding unit) |
---|---|---|---|---|
time | second (s) | hyperfine transition frequency of Cs (ΔνCs) | 9 192 631 770 | Hz |
length | meter (m) | speed of light in vacuum (c) | 299 792 458 | m ⋅ s-1 |
mass | kilogram (kg) | Planck constant (h) | 6.626 070 15 x 10-34 | J ⋅ s |
electric current | ampere (A) | elementary charge (e) | 1.602 176 634 x 10-19 | C |
thermodynamic temperature | kelvin (K) | Boltzmann constant (k) | 1.380 649 x 10-23 | J ⋅ K-1 |
amount of substance | mole (mol) | Avogadro constant (NA) | 6.022 140 76 x 1023 | mol-1 |
luminous intensity | candela (cd) | luminous efficacy (Kcd) | 683 | lm ⋅ W-1 |
table 2019.2 ✧ some derived SI units
derived quantity | unit name | symbol |
---|---|---|
area | square meter | m2 |
volume | cubic meter | m3 |
speed, velocity | meter per second | m/s |
acceleration | meter per second squared | m/s2 |
luminance | candela per square meter | cd/m2 |
table 2019.3 ✧ some derived SI units with special names
derived quantity | unit name | symbol | alt. exp. |
---|---|---|---|
frequency | Hertz | Hz | s-1 |
force | Newton | N | m ⋅ kg ⋅ s-2 |
energy, work, quantity of heat | joule | J | N ⋅ m |
power, radiant flux | Watt | W | J/s |
electric potential difference, electromotive force | Volt | V | W/A |
electric resistance | ohm | Ω | V/A |
Celsius temperature | degree Celsius(d) | °C | °K + 273.16 |
table 2019.4 ✧ some other units designated for use with SI
unit name | symbol | alt. exp. |
---|---|---|
minute | min | 1 min = 60 s |
hour | h | 1 h = 3600 s |
day | d | 1 d = 24 h = 86 400 s |
liter | l, L | 1 l = dm3 = 10-3 m3 (cubic decimeter) |
table 2019.5 ✧ prefixes for binary multiples
factor | name | symbol | origin | derivation |
---|---|---|---|---|
210 | kibi | Ki | kilobinary: (210)1 | kilo: (103)1 |
220 | mebi | Mi | megabinary: (210)2 | mega: (103)2 |
230 | gibi | Gi | gigabinary: (210)3 | giga: (103)3 |
240 | tebi | Ti | terabinary: (210)4 | tera: (103)4 |
250 | pebi | Pi | petabinary: (210)5 | peta: (103)5 |
260 | exbi | Ei | exabinary: (210)6 | exa: (103)6 |
table 2019.6 ✧ comparison of SI and binary prefixes
one kibibit | 1 Kibit = 210 bit = | 1024 bit |
one kilobit | 1 kbit = 103 bit = | 1000 bit |
one mebibyte | 1 MiB = 220 B = | 1 048 576 B |
one megabyte | 1 MB = 106 B = | 1 000 000 B |
one gibibyte | 1 GiB = 230 B = | 1 073 741 824 B |
one gigabyte | 1 GB = 109 B = | 1 000 000 000 B |
aatideas.org document updated:
scale | value | ||
---|---|---|---|
UCN | 12019 S19 Yellow | ||
zone(UT) | t339 tt050 | ||
'ICAS in use' can accommodate calendar and clock formatting 'for all people, for all time'. | |||
AD common year day | 139 | ||
G | 2019 May 19 Sunday | ||
UT | 08:08:14 | ||
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