Statampere

{{Short description|Unit of electric current}}

{{Infobox

| above = statampere

| label2 = Unit system | data2 = CGS-ESU and Gaussian{{cite book |last1=Fenna |first1=Donald |title=A Dictionary of Weights, Measures, and Units |date=2002 |publisher=Oxford University Press |isbn=978-0-19-107898-9 |url=https://books.google.com/books?id=uBk9DAAAQBAJ |language=en}}^{:[https://books.google.com/books?id=uBk9DAAAQBAJ&dq=%22electric%20current.%20Symbol%20statA.%22&pg=PT312 278]}

| label3 = Unit of | data3 = electric current^{:[https://books.google.com/books?id=uBk9DAAAQBAJ&dq=%22electric%20current.%20Symbol%20statA.%22&pg=PT312 278]}

| label4 = Symbol | data4 = statA^{:[https://books.google.com/books?id=uBk9DAAAQBAJ&dq=%22electric%20current.%20Symbol%20statA.%22&pg=PT312 278]}

| label5 = Named after | data5 = A.-M. Ampère

| label6 = In CGS base units | data6 = g{{sup|1/2}}⋅cm{{sup|3/2}}⋅s{{sup|−2}} {{cite book |last1=Gyllenbok |first1=Jan |title=Encyclopaedia of Historical Metrology, Weights, and Measures: Volume 1 |date=2018 |publisher=Birkhäuser |isbn=978-3-319-57598-8 |language=en}}^{:[https://books.google.com/books?id=XnRVDwAAQBAJ&dq=%22Encyclopaedia%20of%20Historical%20Metrology%2C%20Weights%2C%20and%20Measures%22%20vol%201&pg=PA25 26]}

| header7 =Conversions

| data8 = {{val|1|u=statA}} in ...... corresponds to ...

| label9 = SI base units | data9 = {{val|10}}/{{math|c}}{{sub|cgs}} ampere ≈ {{val|3.33564e-10|u=ampere}}{{refn|group="Note"|name="cCGC"|The dimensionless constant {{math|c}}{{sub|cgs}} {{=}} {{val|2.99792458e10}} is numerically equal to the magnitude of the speed of light when the latter is expressed in {{val|u=cm/s}}.}}{{cite book |last1=Cook |first1=James L. |title=Conversion Factors |date=1991 |publisher=Oxford University Press |isbn=978-0-19-856349-5 |url=https://books.google.com/books?id=jRKBQrpXejkC |language=en}}^{:[https://books.google.com/books?id=jRKBQrpXejkC&dq=abamperes%20to%20statamperes&pg=PA16 16]:[https://books.google.com/books?id=XnRVDwAAQBAJ&dq=%22Encyclopaedia%20of%20Historical%20Metrology%2C%20Weights%2C%20and%20Measures%22%20vol%201&pg=PA25 26]}

| label10 = CGS-EMU

| data10 = 1/{{math|c}}{{sub|cgs}} abampere ≈{{val|3.33564e-11|u=abampere}}^{:[https://books.google.com/books?id=jRKBQrpXejkC&dq=abamperes%20to%20statamperes&pg=PA16 16]}

}}

The statampere (statA) is the derived electromagnetic unit of electric current in the CGS-ESU (electrostatic cgs) and Gaussian systems of units.{{cite book |last1=Fenna |first1=Donald |title=A Dictionary of Weights, Measures, and Units |date=2002 |publisher=Oxford University Press |isbn=978-0-19-107898-9 |url=https://books.google.com/books?id=uBk9DAAAQBAJ |language=en}}^{:[https://books.google.com/books?id=uBk9DAAAQBAJ&dq=%22electric%20current.%20Symbol%20statA.%22&pg=PT312 278]}

One statampere corresponds to {{val|10}}/{{math|c}}{{sub|cgs}} ampere{{refn|group="Note"|name="cCGC"}} ≈ {{val|3.33564e-10|u=ampere}} in the SI system of units.

The name statampere is a shortening of abstatampere, where the idea was that the prefix abstat should stand for absolute electrostatic and mean ‘belonging to the CGS-ESU (electrostatic cgs) absolute system of units’.{{refn|group=Note|For quite a long time, the ESU and EMU units didn't have special names; one would just say, e.g. the ESU unit of resistance. It was apparently only in 1903 that A. E. Kennelly suggested that the names of the EMU units be obtained by prefixing the name of the corresponding ‘practical unit' by ‘ab-’ (short for ‘absolute’, giving the ‘abohm’, ‘abvolt’, the ‘abampere’, etc.), and that the names of the ESU units be analogously obtained by using the prefix ‘abstat-’, which was later shortened to ‘stat-’ (giving the ‘statohm’, ‘statvolt’, ‘statampere’, etc.).{{cite journal |last1=Kennelly |first1=A. E. | author-link=Arthur E. Kennelly|title=Magnetic Units and Other Subjects that Might Occupy Attention at the Next International Electrical Congress |journal=Transactions of the American Institute of Electrical Engineers |date=July 1903 |volume=XXII |doi=10.1109/T-AIEE.1903.4764390|url=https://books.google.com/books?id=lTFDAQAAMAAJ&dq=%22The%20expedient%20suggests%20itself%20of%20attaching%20the%20prefix%20ab%20or%20abs%20to%20a%20practical%20or%20Q.%20E.%20S.%20unit%2C%20in%20order%20to%20express%20the%20absolute%20or%20corresponding%20C.%20G.%20S.%20magnetic%20unit.%22&pg=PA1412|pages=529–536|s2cid=51634810 |quote=[p. 534] The expedient suggests itself of attaching the prefix ab or abs to a practical or Q. E. S. unit, in order to express the absolute or corresponding C. G. S. magnetic unit. … [p. 535] In a comprehensive system of electromagnetic terminology, the electric C. G. S. units should also be christened. They are sometimes referred to in electrical papers, but always in an apologetic, symbolical fashion, owing to the absence of names to cover their nakedness. They might be denoted by the prefix abstat. }}{{rp|534–5}} This naming system was widely used in the U.S., but, apparently, not in Europe.{{cite journal | last =Silsbee | first =Francis | title =Systems of Electrical Units | journal = Journal of Research of the National Bureau of Standards Section C | volume =66C | issue =2 | pages =137–183 | date =April–June 1962 | doi =10.6028/jres.066C.014

| doi-access =free}}}}

The esu-cgs (or "electrostatic cgs") units are one of several systems of electromagnetic units within the centimetre–gram–second system of units; others include CGS-EMU (or "electromagnetic cgs units"), Gaussian units, and Heaviside–Lorentz units. In the cgs-emu system, the unit of electric current is the abampere. The unit of current in the Heaviside–Lorentz system doesn't have a special name.

The other units in the cgs-esu and Gaussian systems related to the statampere are:

• statcoulomb – the charge that passes in one second through any cross-section of a conductor carrying a steady current of one statampere
• statvolt – the electrostatic potential difference such that moving a charge of one statcoulomb through it at constant speed requires one erg of work to be done.
• statohm – the resistance of a conductor that, with a constant current of one statampere through it, maintains between its terminals a potential difference of one statvolt