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