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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) |
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
- Parallel Water Filters Like Parallel Resistors
- Resistivity of Metals & Alloys
- Resistors & Resistance Calculations
Posted June 7, 2023 (updated)
Copyright: 1996 - 2026 |
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