Изворни код странице Магнетомоторна сила

{{Електромагнетизам}}
'''Магнетомоторна сила''' је сила која производи [[магнетско поље]] код [[електромагнет]]а.<ref>{{harvnb|Waygood||pp=137}}</ref>

Симбол је обично -{'''F<sub>m</sub>'''}- а јединица је [[ампер-завој]] (ампер-завојак, ампер-навој или ампер-навојак), установљена на бази [[јачина струје|јачине струје]] у једном завоју жице. Пошто ампер-завој није СИ дефинисана јединица, често се једноставно користи Ампер/метар.

Сљедећа формула исказује јачину магнетомоторне силе:<ref>{{harvnb|Smith||pp=495–506}}</ref>

:<math>\mathbf{F_m}=\mathbf{N}\mathbf{I}</math>

где је 

* <math>\mathbf{F_m}</math> магнетомоторна сила у Ампер-завојима, 
* '''-{N}-''' број завоја, и 
* '''-{I}-''' струја у [[ампер]]има.

Јачина [[магнетски флукс|магнетског тока]]<ref>{{Cite book| last1 = Purcell | first1 = Edward |last2 = Morin | first2 = David |title=Electricity and Magnetism |edition=3rd |publisher=Cambridge University Press |location= New York | year= 2013 | isbn=978-1-107-01402-2 | page=278}}</ref><ref>{{Cite book |author = Browne, Michael |title=Physics for Engineering and Science|edition=2nd |publisher=McGraw-Hill/Schaum | year= 2008| isbn=978-0-07-161399-6 |page=235}}</ref> кроз неки материјал зависи о јачини магнетомоторне силе и [[релуктанса|релуктанси]] материјала.<ref>{{cite journal|title=XIV. On magnetic permeability, and the maximum of magnetism of iron, steel, and nickel|author=Rowland, Henry A.|journal=Philosophical Magazine |series=Series 4|volume=46|year= 1873 |issue =304|pages =140–159|doi=10.1080/14786447308640912}}</ref><ref>Rowland, Henry A, [https://www.jstor.org/stable/2369444 "On the general equations of electro-magnetic action, with application to a new theory of magnetic attractions, and to the theory of the magnetic rotation of the plane of polarization of light"] ([https://www.jstor.org/stable/2369465 part 2]), ''American Journal of Mathematics'', vol. 3, nos. 1–2, pp. 89–113, March 1880.</ref><ref>{{cite journal|doi=10.1080/14786448308628457|title=XXVIII.On magnetomotive force|journal=Philosophical Magazine |series=Series 5|volume=15|issue=93|pages=205–217|year=1883|last1=Bosanquet|first1=R.H.M.|url=https://zenodo.org/record/1431167}}</ref> То се може исказати сљедећом једначином:

:<math>\mathbf{\Phi}=\frac{F_m}\mathcal{R} </math>

== Јединице ==

[[International System of Units|СИ јединица]] за -{mmf}- је [[ампер]], исто као и јединица струје (аналогно јединици  [[Electromotive force|-{emf}-]]<ref name="Stewart">{{Cite book|last=Stewart |first=Joseph V. |title=Intermediate electromagnetic theory |url=https://archive.org/details/intermediateelec0000stew |year=2001|publisher=World Scientific |pages=[https://archive.org/details/intermediateelec0000stew/page/389 389]}}</ref><ref name="Tipler803">{{cite book|last=Tipler|first=Paul A.|title=Physics|url=https://archive.org/details/physics00tipl|date=јануар 1976|publisher=Worth Publishers, Inc.|location=New York, NY|isbn=978-0-87901-041-6|pages=[https://archive.org/details/physics00tipl/page/803 803]}}</ref><ref>{{cite journal | journal = Transactions of the American Electrochemical Society | title = The Relation Between Contact Potentials and Electrochemical Action |author=Irving Langmuir | volume = 29 | issue =  | publisher = The Society |pages=175 |year=1916 | url = https://books.google.com/books?id=OW0SAAAAYAAJ&pg=PA172&dq=%22electromotive+force+is+that%22&q=%22electromotive%20force%20is%20that%22 }}</ref> и [[voltage|напона]] [[волт]]). Неформално, и често, ова јединица се наводи као [[ампер-завој]] како би се избегла забуна са струјом. Ово је био назив јединице у систему [[MKS system|МКС]]. Повремено се може срести и [[Electromotive force|-{cgs}-]] системска јединица [[Gilbert (unit)|гилберт]].<ref name=":0">{{Cite book|title = Encyclopaedia of Scientific Units, Weights and Measures. Their SI Equivalences and Origins.|url = https://archive.org/details/encyclopaediasci00card_043|url-access = limited|last = Cardarelli|first = F.|publisher = Springer|year = 2003|isbn = 978-1-4471-1122-1|location = London|pages = [https://archive.org/details/encyclopaediasci00card_043/page/n36 24]}}</ref>

== Историја ==

Термин ''магнетомоторна сила'' је сковао [[Henry Augustus Rowland|Хенри Огастус Ровланд]] 1880. године.<ref>{{cite book| first1= David |last1= Cahan| first2= M. Eugene |last2= Rudd| title= Science at the American Frontier: A Biography of DeWitt Bristol Brace| url= https://archive.org/details/scienceatamerica0000caha | publisher= University of Nebraska Press| year= 2000| page= [https://archive.org/details/scienceatamerica0000caha/page/22 22]| isbn= }}</ref><ref>{{cite book| first1= Jed Z.| last1= Buchwald| title= The Creation of Scientific Effects: Heinrich Hertz and Electric Waves| url= https://archive.org/details/creationscientif00buch_938| publisher= University of Chicago Press| year= 1994| page= [https://archive.org/details/creationscientif00buch_938/page/n368 354]| isbn= }}</ref><ref>{{cite book| first= David |last= Cahan| title= Hermann von Helmholtz and the Foundations of Nineteenth-century Science| publisher= University of California Press| year= 1993| page= 397| isbn= }}</ref> Ровланд је намеравао да ово укаже на директну аналогију са [[electromotive force|електромоторном силом]].<ref>{{multiref|Hon & Goldstein, pp. 638-639|Rowland (1880), pp. 92, 97}}</ref> Идеја о магнетној аналогији са електромоторном силом може се наћи много раније у раду [[Michael Faraday|Мајкла Фарадаја]] (1791-1867), а наговестио ју је у [[Џејмс Клерк Максвел]] (1831-1879). Међутим, Ровланд је сковао тај термин и био је први који је експлицитно навео [[Ohm's law for magnetic circuits|Омов закон за магнетна кола]] 1873. године.<ref>{{multiref|Thompson, p. viii|Rowland (1873), p. 143}}</ref>

''Омов закон за магнетна кола'' се понекад назива Хопкинсоновим законом, а не Ровландовим законом, јер неки аутори приписују закон [[John Hopkinson|Џону Хопкинсону]] уместо Роуланду.<ref>{{multiref|See for instance|Schmidt & Schitter, p. 340, or|Waygood, p. 137}}</ref> Према прегледу метода анализе магнетних кола, ово је нетачна атрибуција која потиче из Хопкинсоновог рада из 1885. године.<ref>Lambert ''et al.'', p. 2427</ref> Штавише, Хопкинсон заправо цитира Ровландов рад из 1873. у овом раду.<ref>{{harvnb|Hopkinson||pp=455}}</ref>

== Примери ==
Треба наћи магнетомоторну силу електромагнета са -{N}-=5 навоја жице кроз које пролази струја од -{I}-=2 А.

<math>\mathbf{F_m}=\mathbf{N}\mathbf{I}</math> = 5 завоја • 2 A = 10 Ампер-завоја.

Ако претпоставимо да је релуктанса магнетног кола <math>\mathcal{R} </math> = 40 000 Ампер-завоја/-{Wb}-, магнетски ток (флукс) кроз магнетско коло јест:

<math>\mathbf{\Phi}=\frac{F_m}\mathcal{R} </math> = <math>\frac{10}{40 000}</math> = 250 -{μWb}-.

== Види још ==
* [[Магнетски флукс|Магнетски ток]]
* [[Густина магнетског флукса|Густина магнетског тока]]
* [[Магнетско поље]]
* [[Електрично поље]]
* [[Максвелове једначине]]
* [[Гаусови закони]]

== Референце ==
{{reflist|}}

== Литература ==
{{Литература|30em}}
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* Hopkinson, John, [http://rstl.royalsocietypublishing.org/content/176/455 "Magnetisation of iron"], ''Philosophical Transactions of the Royal Society'', vol. 176, pp. 455-469, 1885.
* Lambert, Mathieu; Mahseredjian, Jean; Martínez-Duró, Manuel; Sirois, Frédéric, [https://ieeexplore.ieee.org/abstract/document/7008520/ "Magnetic circuits within electric circuits: critical review of existing methods and new mutator implementations"], ''IEEE Transactions on Power Delivery'', vol. 30, iss. 6, pp. 2427-2434, December 2015.
* Rowland, Henry A, [https://archive.org/stream/s4philosophicalm46lond#page/140/mode/2up/ "On magnetic permeability and the maximum magnetism of iron, steel, and nickel"], ''Philosophical Magazine'', series 4, vol. 46, no. 304, pp. 140-159, August 1873.
* Rowland, Henry A, [https://www.jstor.org/stable/2369444 "On the general equations of electro-magnetic action, with application to a new theory of magnetic attractions, and to the theory of the magnetic rotation of the plane of polarization of light"] ([https://www.jstor.org/stable/2369465 part 2]), ''American Journal of Mathematics'', vol. 3, nos. 1-2, pp. 89–113, March 1880.
* Schmidt, Robert Munnig; Schitter, Georg, [https://books.google.co.uk/books?id=3WvnAgAAQBAJ&pg=PA340 "Electromechanical actuators"], ch. 5 in Schmidt, Robert Munnig; Schitter, Georg; Rankers, Adrian; van Eijk, Jan, ''The Design of High Performance Mechatronics'', IOS Press, 2014 {{ISBN|1614993688}}.
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* Smith, R.J. (1966), ''Circuits, Devices and Systems'', Chapter 15, Wiley International Edition, New York.  Library of Congress Catalog Card No. 66-17612
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{{Литература крај}}

== Спољашње везе ==
{{Commons category|Magnetomotive force}}
* [http://www.lightandmatter.com/html_books/0sn/ch11/ch11.html О магнетском пољу] {{Wayback|url=http://www.lightandmatter.com/html_books/0sn/ch11/ch11.html |date=20110603233123 }}

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[[Категорија:Електротехника]]
[[Категорија:Магнетизам]]
[[Категорија:Физичке величине]]