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# 11.3: Conductivity of Some Common Materials

The values below are conductivity $$\sigma$$ for a few materials that are commonly encountered in electrical engineering applications, and for which conductivity emerges as a consideration.

Note that materials in some applications are described instead in terms of resistivity, which is simply the reciprocal of conductivity.

Conductivity may vary significantly as a function of frequency. The values below are representative of frequencies from a few kHz to a few GHz. Conductivity also varies as a function of temperature. In applications where precise values are required, primary references accounting for frequency and temperature should be consulted. The values presented here are gathered from a variety of references, including those indicated in “Additional References” at the end of this section.

Free Space (vacuum): $$\sigma\triangleq 0$$.

Table $$\PageIndex{1}$$: Commonly encountered elements:
Material $$\sigma$$ (S/m)
Copper $$5.8\times 10^7$$
Gold $$4.4\times 10^7$$
Aluminum $$3.7\times 10^7$$
Iron $$1.0\times 10^7$$
Platinum $$0.9\times 10^7$$
Carbon $$1.3\times 10^5$$
Silicon $$4.4\times 10^{-4}$$

## Commonly encountered elements

• Water exhibits $$\sigma$$ ranging from about $$6~\mu$$S/m for highly distilled water (thus, a very poor conductor) to about $$5$$ S/m for seawater (thus, a relatively good conductor), varying also with temperature and pressure. Tap water is typically in the range of 5–50 mS/m, depending on the level of impurities present.
• Soil typically exhibits $$\sigma$$ in the range $$10^{-4}$$ S/m for dry soil to about $$10^{-1}$$ S/m for wet soil, varying also due to chemical composition.
• Non-conductors. Most other materials that are not well-described as conductors or semiconductors and are dry exhibit $$\sigma < 10^{-12}$$ S/m. Most materials that are considered to be insulators, including air and common dielectrics, exhibit $$\sigma < 10^{-15}$$ S/m, often by several orders of magnitude.