- published: 05 Nov 2014
- views: 340
The siemens (SI unit symbol: S) is the unit of electric conductance, electric susceptance and electric admittance in the International System of Units (SI). Conductance, susceptance, and admittance are the reciprocals of resistance, reactance, and impedance respectively; hence one siemens is equal to the reciprocal of one ohm, and is also referred to as the mho. The 14th General Conference on Weights and Measures approved the addition of the siemens as a derived unit in 1971.
The 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 upper case (S); the lower-case "s" is the symbol for the second. When an SI unit is spelled out in English, it should always begin with a lower-case letter (siemens), except where any word would be capitalized. In English, the same form siemens is used both for the singular and plural.
For a conducting or semiconducting element, electrical resistance R and electrical conductance G are defined as
Siemens AG (German pronunciation: [ˈziːmɛns]) is a German multinational conglomerate company headquartered in Berlin and Munich and the largest engineering company in Europe.
The principal divisions of the company are Industry, Energy, Healthcare, and Infrastructure & Cities, which represent the main activities of the company. The company is a prominent maker of medical diagnostics equipment and its medical health-care division, which generates about 12 percent of the company's total sales, is its second-most profitable unit, after the industrial automation division. The company is a component of the Euro Stoxx 50 stock market index. Siemens and its subsidiaries employ approximately 362,000 people worldwide and reported global revenue of around €71.9 billion in 2014 according to their annual report.
Siemens & Halske was founded by Werner von Siemens and Johann Georg Halske on 12 October 1847. Based on the telegraph, his invention used a needle to point to the sequence of letters, instead of using Morse code. The company, then called Telegraphen-Bauanstalt von Siemens & Halske, opened its first workshop on October 12.