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# Resistivity (ρ) & Conductivity (σ) of Metals and Alloys

Resistivity, also referred to as specific resistance, is dependent on the nature of the material as well as its volume definition (shape and size). Resistivity is expressed in units that are the product of resistance and length; e.g., Ω·cm. The symbol most commonly used for resistivity is rho (ρ).

Conductivity is the reciprocal of resistivity. Conductivity is expressed in units that are the quotient of conductance (Siemens) and length; e.g., S/cm. The symbol most commonly used for resistivity is sigma (σ).

As an example of calculating a volume's resistance, consider the drawing to the left. Assume 12 AWG copper wire with a resistivity (from the table) of
1.72x10-6 Ω·cm, a cross-sectional area (A) of 0.03309 cm2, and a length of 1 meter. Per the given formula, its resistance is:

,

which agrees well with typical specified Ω/km values published by wire manufacturers. Alpha claims 1.59 Ω/1000' or 5.22 Ω/km.

The table of resistivity values below are pulled from the Wikipedia website. A wide variation in values can be found in various sources, so verify the accuracy with a trusted source if critical work is being done.

 Material Resistivity, ρ@ 20 °C (Ω·m) Conductivity, σ@ 20 °C (S/m) TemperatureCoefficient(K-1) Air 1E9 to 1E15 1E-15 to 1E-9 Aluminum 2.65E-8 3.77E7 3.93E-3 Annealed copper 1.72E-8 5.80E7 3.93E-3 Arsenic 3.50E-7 2.86E6 Bismuth 129E-8 7.75E5 Boron 1.80e10 5.56E-11 Brass (30% Zn) 5.99E-8 1.67E7 Brass (5% Zn) 3.00E-8 3.34E7 Calcium 3.36E-8 2.98E7 4.10E-3 Carbon (amorphous) 0.5E-3 to 0.8E-3 1.25E3 to 2.00E3 -0.50E-3 Carbon (diamond) 1E12 10-13 Carbon (graphite†) 250E-8 to 500E-8 2E5 to 3E5 Carbon (graphite††) 3.0E-3 3.3E2 Carbon steel (1010) 14.3E-8 6.99E6 Cobalt 6.24E-8 1.60E7 7.00E-3 Constantan 49.0E-8 2.04E6 0.008E-3 Copper 1.68E-8 5.96E7 4.04E-3 Deionized water 1.8E5 4.2E-5 Drinking water 2E1 to 2E3 5E-4 to 5E-2 Fused quartz 7.5E17 1.3E-18 Gallium 14.0E-8 7.10E6 4.00E-3 Germanium 4.6E-1 2.17 -48.0E-3 Glass 1E11 to 1E15 1E-15 to 10-11 Gold 2.44E-8 4.11E7 3.40E-3 Steel (electrical, grain-oriented) 46.0E-8 2.17E6 Hard rubber 1E13 1E-14 Iron 9.70E-8 1.03E7 5.00E-3 Lead 22.0E-8 4.55E6 Lithium 9.28E-8 1.08E7 6.00E-3 Manganese 144E-8 6.94E5 Manganin 48.2E-8 2.07E6 0.002E-3 Mercury 98.0E-8 1.02E6 0.90E-3 Nichrome 110E-8 6.70E5 0.40E-3 Nickel 6.99E-8 1.437 6.00E-3 Niobium 14.0E-8 7.006 PET 1E21 1E-21 Phosphor Bronze (0.2% P / 5% Sn) 11.2E-8 8.94E6 Platinum 10.6E-8 9.436 3.92E-3 Plutonium (0 °C) 146E-8 6.855 PTFE (Teflon) 1E23 to 1E25 1E-25 to 1E-23 Rhodium 4.33E-8 2.31E7 Ruthenium 7.10E-8 1.41E7 Sea water 2.1E-1 4.8 Silicon 2.30E3 4.35E-4 -75.0E-3 Silver 1.59E-8 6.30E7 3.80E-3 Stainless steel 69.0E-8 1.45E6 0.94E-3 Sulfur 1E15 10-16 Swimming pool water 3.3E-1 to 4.0E-1 0.25 to 0.30 Tantalum 1.37E-7 7.63E7 Tin 10.9E-8 9.17E6 4.50E-3 Titanium 42.0E-8 2.38E6 3.80E-3 Tungsten 5.60E-8 1.79E7 4.50E-3 Ultrapure water 1.82E09 5.49E-10 Wood (damp) 1E3 to 1E4 1E-4 to 1E-3 Wood (oven dry) 1E14 to 1E16 1E-16 to 1E-14 Zinc 5.90E-8 1.69E7 3.70E-3

† parallel to basal plane

†† perpendicular to basal plane

Posted June 7, 2023 (updated)