Copper greater strength than monocrystalline forms. The softness of copper partly explains its high electrical conductivity (59.6×10 S/m) and high thermal conductivity, second highest (second only to silver) among pure metals at room temperature. This is because the resistivity to electron transport in metals at room temperature originates primarily from scattering of electrons on thermal vibrations of the lattice, which are relatively weak in a soft metal. The maximum permissible current density of copper in open air is approximately 3.1×10 A/m of cross-sectional area, above which it begins to heat excessively. Copper is one of a few metallic elements with a
Conductivity near the percolation threshold of the perfect insulator and just finite metallic clusters. The exponent t is one of the two critical exponents for electrical percolation. In the other well-known case of a superconductor-conductor mixture we have formula_18. This case is useful for the description below the percolation threshold: formula_19 for formula_20 Now, above the percolation threshold the conductivity becomes infinite, because of the infinite superconducting clusters. And also we get the second critical exponent s for the electrical percolation. In the region around the percolation threshold, the conductivity assumes a scaling form: formula_21 with formula_22 and formula_23 At the percolation threshold, the conductivity