If you calculate the resistance of a copper conductor using resistivity and the cross sectional area, you get a value that does not match the resistance given for the same conductor in the NEC. Does anyone know why?
ex. #2/0 in the NEC is .11 ohms/ 1000 ft.
if you take row *length/ area you get .0833 ohms/1000ft.
2006-10-24 05:48:24 · 2 answers · asked by tightlies 3 in Science & Mathematics ➔ Engineering
NEC code is probably more stringent. Dont forget too, there are differing types of copper, insulation that will allow different types of cooling, etc.
I havent done the calculation, but it wouldnt suprise me that 'pure' copper has a somewhat better resistance than published specs of any kind. Wire manufacturers derate wires too
2006-10-24 06:46:20 · answer #1 · answered by designer_brian 2 · 0⤊ 0⤋
The national electric Code (united states) shows the resistance of a sturdy #10 AWG (lined) conductor, at seventy 5 tiers C, is unquestionably a million.26 ohms/one thousand ft.. The resistance of a conductor somewhat relies upon on the temperature of the conductor. The resistivity of copper is oftentimes expressed for the conductor having a temperature of 20 tiers C. the particular situation of the NEC i'm finding at is the 1984 situation. I had it out for reference on yet another query. despite if, the resistance of copper and twine length are fastened by way of nature and guy, so I doubt the two has replaced when you consider that then. in case you have this e book, look in Tables And Examples, table 8. EDIT Corrected 126 to a million.26 TexMav
2016-12-08 20:21:54 · answer #2 · answered by ? 4 · 0⤊ 0⤋