Conductivity, Resistivity and Temperature Coefficients for some Common Materials

The factor in the resistance which takes into account the nature of the material is the resistivity.

Material	Resistivity Coefficient      - ρ - (ohm m)	Temperature Coefficient per degree C	Conductivity             - σ - (1 /Ωm)
Aluminum	2.65 x 10-8	3.8 x 10-3	3.77 x 107
Antimony	41.8 x 10-8
Beryllium	4.0 x 10-8
Bismuth	115 x 10-8
Cadmium	7.4 x 10-8
Carbon (graphite)1)	3 - 60 x 10-5	-4.8 x 10-3
Chromel (alloy of chromium and aluminum)		0.58 x 10-3
Chromium	13 x 10-8
Cobalt	9 x 10-8
Constantan	49 x 10-8	0	0.20 x 107
Copper	1.724 x 10-8	4.29 x 10-3	5.95 x 107
Eureka		0.1 x 10-3
Iron	9.71 x 10-8	6.41 x 10-3	1.03 x 107
Germanium1)	1 - 500 x 10-3	-50 x 10-3
Glass	1 - 10000 x 109
Gold	2.24 x 10-8
Iridium	5.3 x 10-8
Iron	9.7 x 10-8
Lead	20.6 x 10-8		0.45 x 107
Magnesium	4.45 x 10-8
Manganese	185 x 10-8
Mercury	98.4 x 10-8	8.9 x 10-3	0.10 x 107
Molybdenum	5.2 x 10-8
Nickel	6.85 x 10-8	6.41 x 10-3
Nichrome (alloy of nickel and chromium)		0.40 x 10-3
Niobium (Columbium)	13 x 10-8
Osmium	9 x 10-8
Platinum	10.5 x 10-8	3.93 x 10-3	0.943 x 107
Plutonium	141.4 x 10-8
Potassium	7.01 x 10-8
Quartz (fused)	7.5 x 1017
Rhodium	4.6 x 10-8
Rubber - hard	1 - 100 x 1013
Selenium	12.0 x 10-8
Silicon1)	0.1-60	-70 x 10-3
Silver	1.59 x 10-8	6.1 x 10-3	6.29 x 107
Sodium	4.2 x 10-8
Tantalum	12.4 x 10-8
Thorium	18 x 10-8
Tin	11.0 x 10-8
Titanium	43 x 10-8
Tungsten	5.65 x 10-8	4.5 x 10-3	1.79 x 107
Uranium	30 x 10-8
Vanadium	25 x 10-8
Zinc	5.92 x 10-8

¹⁾ The resistivity depends strongly on the presence of impurities in the material
²⁾ Resistivity and Temperature Coefficients at 20^oC reference

Resistivity

The electrical resistance of a wire is greater for a longer wire and less for a wire of larger cross sectional area. The resistance depend on the material of which it is made and can be expressed as:

R = ρ L / A         (1)
where
R = resistance (ohm)
ρ = resistivity coefficient (ohm m)
L = length of wire (m)
A = cross sectional area of wire (m²)

The factor in the resistance which takes into account the nature of the material is the resistivity. Since it is temperature dependent, it can be used to calculate the resistance of a wire of given geometry at different temperatures.

Conductivity

The inverse of resistivity is called conductivity and can be expressed as:

σ = 1 / ρ         (2)
where
σ = conductivity (1 / Ω m)

Resistance

The electrical resistance of a circuit component or device is defined as the ratio of the voltage applied to the electric current which flows through it:

R = V / I         (3)
where
R = resistance (ohm)
V = voltage (V)
I = current (A)

Ohm's Law

If the resistance is constant over a considerable range of voltage, then Ohm's law,

I = V / R         (4)

can be used to predict the behavior of the material.

Temperature Coefficient

The electrical resistance increases with temperature. An intuitive approach to temperature dependence leads one to expect a fractional change in resistance which is proportional to the temperature change:

dR / R_s = α dT         (5)
where
dR = change in resistance (ohm)
R_s = standard resistance according reference tables (ohm)
α = temperature coefficient of resistance
dT = change in temperature (K)