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+---
+id: 2026-05-19T09:48:52-0400
+title: 2026-05-19 09:48:52
+tags: []
+daily: "[[2026-05-19]]"
+---
+# 2026-05-19 09:48:52
+
+## Wire Properties
+
+### Resistance
+
+NEC Chapter 9 Tables [[nfpa-70_ch09#Table 8 Conductor Properties|8]]
+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|9]]
+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)](https://en.wikipedia.org/wiki/International_Annealed_Copper_Standard),
+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.