# Conductor Bulk Resistivity & Skin Depths

Available bulk resistivity values (ρ) and relative permeability (μr)used to calculate skin depths (δσ) can vary considerably depending on the source. In fact, the values for permeabilities are so far-ranging that I hesitated to even include any of them in the table. The ones used here are typical, gathered from many of the links listed at the bottom of the page. Therefore, it is incumbent upon the user to determine his own value based on a trusted source. Even NIST[1] and CRC[2] do not fully agree on bulk resistivity values for materials as well-known as copper and aluminum. Most common conductors used in cabling have a relative permeability of very near unity (1).

Note that ferromagnetic materials often experience a falloff in relative permeability as frequency increases. For example least one investigator[3] has measured a value as low as 1 for nickel at 10 GHz.

Here is the equation for skin depth
Here is a skin depth calculator

 Material ChemicalFormula BulkResistivity@20CµΩ×cm(Ω×10-8m) RelativePermeabilityμ/μ0 Skin Depth(µm@f) 1MHz 10MHz 100MHz 1GHz 10GHz 100GHz Aluminum Al 2.65 1 81.9 25.9 8.19 2.59 0.819 0.259 Beryllium Be 3.3 1 91.4 28.9 9.14 2.89 0.914 0.289 Brass Cu70/Zn30 7 1 133 42.1 13.3 4.21 1.33 0.421 Bronze Cu89/Sn11 15 1 195 61.6 19.5 6.16 1.95 0.616 Carbon C (graphite) 1375 1866 590 187 59.0 18.7 5.90 Cadmium Cd 7.3 136 43.0 13.6 4.30 1.36 0.430 Chromium Cr 13.2 1 183 57.8 18.3 5.78 1.83 0.578 Cobalt Co 6.34 600 5.8 1.6 0.52 0.16 0.052 0.016 Constantan Cu60Ni40 49 352 111 35.2 11.1 3.52 1.11 Copper Cu 1.69 1 65.4 20.7 6.54 2.07 0.654 0.207 Dural Al95/Cu 4/Mg 1 5 112.54 35.6 11.3 3.56 1.13 0.356 Gallium Ga 15.5 198 62.7 19.8 6.27 1.98 0.627 Gold Au 2.2 1 74.7 23.6 7.47 2.36 0.747 0.236 Graphite C 783.7 1409 446 141 44.6 14.1 4.46 Inconel alloy 600 Ni72/Cr16/Fe 8 103 1 511 162 51.1 16.2 5.11 1.62 Indium In 8.8 149 47.2 14.9 4.72 1.49 0.472 Iridium Ir 5.1 114 35.9 11.4 3.59 1.14 0.359 Iron Fe 10.1 500 7.2 2.3 0.72 0.23 0.072 0.023 Lead Pb 20.6 1 228 72.2 22.8 7.22 2.28 0.722 Lithium Li 9.29 153 48.5 15.3 4.85 1.53 0.485 Magnesium Mg 4.2 1 103 32.6 10.3 3.26 1.03 0.326 Mercury Hg 95.9 1 493 156 49.3 15.6 4.93 1.56 Molybdenum Mo 5.7 1 120 38.0 12.0 3.80 1.20 0.380 Monel alloy 400 Ni65/Cu33/Fe 2 49 352 111 35.2 11.1 3.52 1.11 mu-Metal 47 30,000 2.0 0.64 0.20 0.064 0.020 0.0064 Nickel Ni 6.9 200 9.3 3.0 0.93 0.30 0.093 0.030 Nichrome Ni80/Cr20 108 523 165 52.3 16.5 5.23 1.65 Palladium Pd 10.8 1 165 52.3 16.5 5.23 1.65 0.523 Platinum Pt 10.58 1 164 51.8 16.4 5.18 1.64 0.518 Potassium K 6.8 131 41.5 13.1 4.15 1.31 0.415 Rhodium Rh 4.7 1 109 34.5 10.9 3.45 1.09 0.345 Silver Ag 1.63 1 64.3 20.3 6.43 2.03 0.643 0.203 Sodium Na 4.9 111 35.2 11.1 3.52 1.11 0.352 Steel 100 Tantalum Ta 13.5 185 58.5 18.5 5.85 1.85 0.585 Tantalum Nitride TaN 252 799 253 79.9 25.3 7.99 2.53 Tin (pure) Sn 12.6 1 179 56.5 17.9 5.65 1.79 0.565 Titanium Ti 54 1 370 117 37.0 11.7 3.70 1.17 Tungsten W 5.4 1 117 37.0 11.7 3.70 1.17 0.370 Urnaium U 27 262 82.7 26.2 8.27 2.62 0.827 Yttrium Y 53 366 116 36.6 11.6 3.66 1.16 Zinc Zn 5.96 123 38.9 12.3 3.89 1.23 0.389 Zirconium Zr 44 334 106 33.4 10.6 3.34 1.06

1: National Institute of Standards and Technology

2: Chemical Rubber Corporation

3: Microwave Characterization of Nickel, Stepan Lucyszyn, Imperial College London (thanks to Reto Z. for pointing this out)

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