Dictionary:
sie·mens (sē'mənz) ![]() |
A unit of electrical conductance in the International System, equal to one ampere per volt.
[After Ernst Werner von SIEMENS.]
Dictionary:
sie·mens (sē'mənz) ![]() |
A unit of electrical conductance in the International System, equal to one ampere per volt.
[After Ernst Werner von SIEMENS.]
| 5min Related Video: siemens |
| Medical Dictionary: sie·mens |
A unit of electrical conductance in the International System of Units, equal to one ampere per volt.
| Veterinary Dictionary: siemens |
The SI unit of conductivity, equal to one reciprocal ohm (Ω−1); symbol S. Called also mho.
| WordNet: siemens |
The noun has one meaning:
Meaning #1:
a unit of conductance equal to the reciprocal of an ohm
Synonyms: mho, reciprocal ohm, S
| Wikipedia: Siemens (unit) |
The siemens (symbol: S) is the SI derived unit of electric conductance. It is equal to inverse ohm. It is named after the German inventor and industrialist Ernst Werner von Siemens, and was previously called the mho. In English, the term siemens is used both for the singular and plural. The 14th General Conference on Weights and Measures approved the addition of the siemens as an SI derived unit in 1971.
This SI unit is named after Ernst Werner von Siemens. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is uppercase (S). When an SI unit is spelled out in English, it should always begin with a lowercase letter (siemens), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.
—Based on The International System of Units, section 5.2.
Contents |
| Submultiples | Multiples | |||||
|---|---|---|---|---|---|---|
| Value | Symbol | Name | Value | Symbol | Name | |
| 10–1 S | dS | decisiemens | 101 S | daS | decasiemens | |
| 10–2 S | cS | centisiemens | 102 S | hS | hectosiemens | |
| 10–3 S | mS | millisiemens | 103 S | kS | kilosiemens | |
| 10–6 S | µS | microsiemens | 106 S | MS | megasiemens | |
| 10–9 S | nS | nanosiemens | 109 S | GS | gigasiemens | |
| 10–12 S | pS | picosiemens | 1012 S | TS | terasiemens | |
| 10–15 S | fS | femtosiemens | 1015 S | PS | petasiemens | |
| 10–18 S | aS | attosiemens | 1018 S | ES | exasiemens | |
| 10–21 S | zS | zeptosiemens | 1021 S | ZS | zettasiemens | |
| 10–24 S | yS | yoctosiemens | 1024 S | YS | yottasiemens | |
| Common multiples are in bold face. | ||||||
For a physical object, typically an electronic device, with electrical resistance R, the conductance G is defined as

where I is the electric current through the object and V is the voltage (electrical potential difference) across the object.
The unit siemens for the conductance G is defined by

Note that the last term is in SI base units where A is the symbol for ampere, the unit of electric current; kg is the symbol for kilogram, the unit of mass; m is the symbol for metre, the unit of length; and s is the symbol for the time unit second. C is the symbol for the SI derived unit of electric charge, the coulomb; V is the symbol for the SI derived unit of voltage, the volt; and Ω is the symbol for the SI derived unit of electrical resistance, the ohm.
For a device with a conductance of one siemens, the electric current through the device will increase by one ampere for every increase of one volt of electric potential difference across the device.
Example: The conductance of a resistor with resistance six ohms is G = 1/(6 Ω)
0.167 S.
Since 1860 to the middle of 20th century, siemens or siemens mercury unit, was the unit of electrical resistance. It was defined as the resistance of a mercury column 1 meter long and 1 mm2 c.s.a. at 0 degrees Celsius. It was equivalent to 0.953 Ohm approximately. Officially, it ceased usage after 1881, but was widely used in telegraph and telephone services until World War II.
The siemens was previously referred to by the term mho, which was derived from spelling ohm backwards and written with an upside-down capital Greek letter Omega:
, Unicode symbol U+2127 (℧). The term siemens, as it is an SI unit, is used universally in science and primarily in electrical applications, while mho is still used primarily in electronic applications. The inverted Omega, while not an official SI abbreviation, has the advantage of being less likely to be confused with a variable than the letter S when doing algebraic calculations by hand, where the usual typographical distinctions (such as italic for variables and Roman for unit names) are difficult to maintain. Likewise, it is difficult to distinguish the symbol S from the lower case s where second is meant, potentially causing confusion.
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
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Copyrights:
![]() | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved. Read more | |
![]() | Medical Dictionary. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Read more | |
![]() | Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more | |
![]() | WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. Read more | |
![]() | Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Siemens (unit)". Read more |
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