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id, title, tags, daily
| id | title | tags | daily |
|---|---|---|---|
| 2026-05-19T09:48:52-0400 | 2026-05-19 09:48:52 | 2026-05-19 |
2026-05-19 09:48:52
Wire Properties
Resistance
NEC Chapter 9 Tables nfpa-70_ch09#Table 8 Conductor Properties and nfpa-70_ch09#Table 9 Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60 Hz, 75°C (167°F) — Three Single Conductors in Conduit provide resistance values for sizes and materials of wires, stated in their notes to be based on calculations found in nbs_1966_handbook-100 and nbs_1972_handbook-109.
International Annealed Copper Standard
The same tables give conductor conductivity as a percent of International Annealed Copper Standard (IACS), viz. 100% for copper and 61% for aluminum.
The definition of the IACS, as originally published in nbs_1914_circular-031 is
100\%\ \rm{IACS} \equiv 0.15328~\text{ohm (meter, gram) at 20°C},
alternately denoted in nbs_1966_handbook-100 as
0.15328~\text{ohm-gram/meter$^2$ at 20°C}.
These definitions are for mass resistivity.
Volume resistivity can be derived using the density of copper at the same temperature,
8.89~\text{gram/cm$^3$ at 20°C},
or
0.32117~\text{lb/in.$^3$ at 20°C}.
The derived value of volume resistivity given by nbs_1966_handbook-100 is
0.017241~\text{ohm-mm$^2$/meter at 20°C}.
equal to 58 S/mm at 20°C.