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MECA Electronics

Resistivity (ρ) & Conductivity (σ) of Metals, Alloys, Rocks, and Soils

Resistivity of Metals, Alloys, Rocks, and Soils - 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 Reference Data for Radio Engineers, 1995, Sams Publishing. Please verify accuracy with a second source. See rocks and soils table at bottom. Interesting note: The nickel-silver compound actually contains no silver at all; its name is derived from a silver appearance.

 

Metal & Alloy MaterialsFormResistivity
(x10-6 Ω·cm)
Temperature
(°C)
Temperature
Coefficient (°C-1)
Alumelsolid33.300.0012
Aluminumliquid
solid
20.3
2.62
670
20

.0039
Antimonyliquid
solid
123
39.2
800
20

0.0036
Arsenicsolid3500.0042
Berylliumsolid4.5720 
Bismuthliquid
solid
128.9
115
300
20

0.004
Boronsolid1.8x10120 
Brass (66 Cu, 34 Zn)solid3.9200.002
Cadmiumliquid
solid
34
7.5
400
20

0.0038
Carbondiamond
graphite
graphene
5x1020
1400
15
20

-0.0005
Ceriumsolid7820 
Cesiumliquid
solid
36.6
20
30
20
 
Chromax (15 Cr, 35 Ni, balance Fe)solid100200.00031
Chromelsolid70-11000.00011-0.000054
Chromiumsolid2.60 
Cobaltsolid9.7200.0033
Constantan (55 Cu, 45 Ni)solid44.2200.0002
Copper (annealed)liquid
solid
21.3
1.7241
1083
20

0.0039
Galliumsolid
liquid
27
53
30
0
 
Goldliquid
solid
30.8
2.44
1063
20

0.0034
Granitesolid1x1013 - 1x1015  
Hafniumsolid32.120
Indiumliquid
solid
29
9
157
20

0.00498
Iridiumsolid5.3200.0039
Ironsolid9.71200.0052-0.0062
Kovar A (29, Ni, 17 Co, 0.3 Mn, balance Fe)solid45-8420 
Lava flow (basic)
Lava, fresh
liquid1x1012 - 1x1013  
Leadliquid
solid
98
21.9
400
20

0.004
PbO2solid92  
Lithiumliquid
solid
45
9.3
230
20
0.003
0.005
Magnesiumsolid4.46200.004
Manganesesolid520 
MnO2solid600000020 
Magnanin (84 Cu, 12 Mn, 4 Ni)solid4420±0.0002
Mercuryliquid
solid
95.8
21.3
20
-50
0.00089
Molybdenumsolid5.17
4.77
0
20

0.0033
Monel metal (67 Ni, 30 Cu, 1.4 Fe)solid42200.002
Neodymiumsolid7918 
Nichrome (65 Ni, 12 Cr, 23 Fe)solid100200.00017
Nickelsolid6.9200.0047
Nickel-Silver (64 Cu, 18 Zn, 18 Ni)solid28200.00026
Niobiumsolid12.420 
Osmiumsolid9200.0042
Palladiumsolid10.8200.0033
Phosphor bronze (4 Sn, 0.5 P, balance Cu)solid9.4200.003
Platinumsolid10.5200.003
Plutoniumsolid15020 
Potassiumliquid
solid
13
7
62
20

0.006
Praseodymiumsolid6825 
Rheniumsolid19.820 
Rhodiumsolid5.1200.0046
Rubidiumsolid12.520 
Rutheniumsolid1020 
Seleniumsolid1.220 
Silversolid1.62200.0038
Sodiumliquid
solid
9.7
4.6
100
20
 
Steel (0.4-0.5 C, balance Fe)solid13-22200.003
Steel, manganese (13 Mn, 1 C, 86 Fe)solid70200.001
Steel, stainless (0.1 C, 18 Cr, 8 Ni, balance Fe)solid9020 
Strontiumsolid2320 
Sulfursolid2x102320 
Tantalumsolid13.1200.003
Thalliumsolid18.1200.004
Thoriumsolid18200.0021
Tinsolid11.4200.0042
Titaniumsolid47.825 
Tophet A (80 Ni, 20 Cr)solid108200.00014
Tungstensolid5.48200.0045
W2O5solid45020 
WO3solid2x101120 
Uraniumsolid2900.0021
Zincliquid
solid
35.3
6
420
20

0.0037
Zirconiumnsolid40200.0044

 

Rock & Soil MaterialsResistivity
(x10 Ω·cm)
Granite107 - 109
Lava flow (basic)
Lava, fresh
106 - 107
3x105 - 106
Marble
Marble, white
Marble, yellow
4x108
1010
1010
Quartz, vein, massive>106
Schist, mica107
Shale, bed
Shale, nonesuch
105
104
Limestone
Limestone, Cambrian
104
104 - 105
Sandstone
Sandstone, eastern
105
3x103 - 104
Clay, blue
Clay, fire
2x104
2x105
Clayey earth104 - 4x104
Gravel105
Sand, dry
Sand, moist
105 - 106
106 - 105

 

 

 

Posted July 13, 2018

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