Resistivity and temperature coefficient


The electrical resistivity ρ (Rho (letter)) of a material is given by

{\rho={R \left. \frac{A}{\ell} \right.}}

where

ρ is the static resistivity (measured in ohm metres, Ω-m);
R is the electrical resistance of a uniform specimen of the material (measured in ohms, Ω);
\ell is the length of the piece of material (measured in meters, m);
A is the cross-sectional area of the specimen (measured in square meters, m²).

The standard is to measure in m2, but be warned that often you might need cm2 or sq mils.

Material Resistivity (Ω-m) at 20 °C Coefficient*
Silver 1.59×10-8 .0038
Copper 1.72×10-8 .0039
Gold 2.44×10-8 .0034
Aluminium 2.82×10-8 .0039
Calcium 3.3x10-8
Tungsten 5.60×10-8 .0045
Nickel 6.99×10-8 ?
Iron 1.0×10-7 .005
Tin 1.09×10-7 .0045
Platinum 1.1×10-7 .00392
Lead 2.2×10-7 .0039
Manganin 4.82×10-7 .000002
Constantan 4.9×10-7 .00001
Lead 2.2×10-7
Mercury 9.8×10-7 .0009
Nichrome 1.10×10-6 .0004
Carbon 3.5×10-5 -.0005
Germanium 4.6×10-1 -.048
Silicon 6.40×102 -.075
Glass 1010 to 1014 ?
Hard rubber approx. 1013 ?
Sulfur 1015 ?
Paraffin 1017 ?
Quartz (fused) 7.5×1017 ?
PET 1020 ?
Teflon 1022 to 1024 ?

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