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Electrical resistivity

Electrical resistivity (also known as specific electrical resistance) is a measure indicating how strongly a material opposes the flow of electric current; if the resistivity of the material is small, that means that material is effective to carry electrons.

The resistivity of a material is usually denoted by the lower-case Greek letter rho (ρ) and is given by RS/l, where R is the resistance of a uniform specimen of the material, having a length l and a cross-section area S. The units of ρ are ohm meters. Its reciprocal quantity is electrical conductivity.

Also the resistivity is the magnitude of the electric field divided by the magnitude of the current density[?].

In general, electrical resistivity of metals increases with temperature, while the resistivity of semiconductors decreases with temperature.

Some materials lose all electrical resistivity under certain conditions; this effect is known as superconductivity.

The table of resistivity for various materials (at 20 degree):

MaterialResistivity (Ohm-meters)
Silver1.59 x 10-8
Copper1.7 x 10-8
Gold2.44 x 10-8
Aluminum2.82 x 10-8
Tungsten5.6 x 10-8
Iron10 x 10-8
Platinum11 x 10-8
Lead22 x 10-8
(A nickel-chromium alloy commonly used in heating elements)
1.50 x 10-6
Carbon3.5 x 10-5
Glass1010 to 1014
Hard rubber[?]approximately 1013
Quartz (fused)75 x 16

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