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

Resistivity of Metals and Alloys - RF CafeResistivity, 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 (S/cm) - RF CafeConductivity 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:

Resistance per kilometer of 12 AWG copper wire - RF Cafe,

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)
Temperature
Coefficient
(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)

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Webmaster:

    Kirt Blattenberger,

    BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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