Електрическо съпротивление

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Класическа електродинамика
Известни учени

Електрическото съпротивление е физична величина, характеризираща способността на материалите да се съпротивляват на електрическия ток, който протича през тях. Прието е да се означава с R или r.

Съпротивлението при постоянен ток се определя като отношението на електрическата потенциална разлика към тока в проводник, в който няма електродвижещо напрежение.

Законът на Ом за съпротивлението на част от веригата е[1]:

.

При това различаваме постоянна стойност на съпротивлението или моментна стойност (при промяна на тока или напрежението с времето)[2].

Активното съпротивление при променлив ток е реалната част от комплексното съпротивление (импеданса).

Реактанс (реактивно съпротивление) се нарича имагинерната част от комплексното съпротивление.

Измервателната единица за електрическо съпротивление според системата SI е ом и се означава с гръцката буква Ω. 1 Ω (един ом) е електрическото съпротивление на проводник, върху който ток от 1 A (един ампер) предизвиква пад на напрежение 1 V (един волт).

Понастоящем най-точното възпроизвеждане на единицата става с помощта на квантовия ефект на Хол, като еталонът се намира при температура под 4 К.

Източници

  1. ↑ IEC 60050-131, Международен електротехнически речник
  2. ↑ ISO/IEC 80000-6, Величини и единици − част 6: Електромагнетизъм, 2008; термин 6-46

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