Electrical conductivity in metals

Electrical conductivity in metals apparently depends upon the smooth and uninterrupted movement of electrons through the lattice. This is suggested by the feet that small amounts of impurities reduce the conductivity very much. We shall see, in Chapter 22, that copper is purified commercially to 99.999% and the reason is directly connected to the consequent gain in electrical conductivity. 

Electrical conduction in metals can be explained in terms of molecular orbitals that spread throughout the solid. We have already seen that, when N atomic orbitals merge together in a molecule, they form N molecular orbitals. The same is true of a metal but, for a metal, N is enormous (about 1023 for 10 g of copper, for example). Instead of the few molecular orbitals with widely spaced energies typical of small molecules, the huge number of molecular orbitals in a metal are so close together in energy that they form a nearly continuous band (Fig. 3.43). 

Electrical conduction in metals and alloys occms by the motion of electrons. It can be shown that the conductivity is proportional to the number of electrons per unit volume, Ug, the charge per electron, qg, and the electron mobility, pLg ... 

The wave vector, k, is the key to understanding electrical conductivity in metals. For this purpose, it is important to note that it is a vector with direction as well as... 

FIGURE 21.10 Bands of MO energy levels for (a) a metallic conductor, (b) an electrical insulator, and (c) a semiconductor. A metallic conductor has a partially filled band. An electrical insulator has a completely filled valence band and a completely empty conduction band, which are separated in energy by a large band gap. In a semiconductor, the band gap is smaller. As a result, the conduction band is partially occupied with a few electrons, and the valence band is partially empty. Electrical conductivity in metals and semiconductors results from the presence of partially filled bands. 

How does temperature normally affect electrical conductivity in metals ... 

Transfer of an electric current through a solid or liquid (electrical conduction). In metallic or electronic conductors the current is carried by a flow of electrons, the atomic nuclei remaining stationary. This type of conduction is common to all metals and alloys, carbon and graphite, and certain solid com-... 

Electrolytic conductance is different from electrical conductance in metal. Electronic conductance is called a Class I conductor, while electrolytic conductance is a Class 11 conductor. Both inorganic and organic salts, acids or alkalis can be used to increase the... 

QUANTIZATION OF ELECTRICAL CONDUCTANCE IN METAL-SEMICONDUCTOR NANOCONTACTS... 

Greenwood DA (1958) The Boltzmann equation in the theory of electrical conduction in metals. Proc Phys Soc Lond 71(460) 585-596... 

Alkali metal atoms in the crystal have half as many electrons as can be housed in the delocalized molecular orbital band. The presence of partially filled bands accounts for bonding and electrical conduction in metals. The application of an small potential difference between two regions of the metal is enough for... 

Bridgman, Percy Williams (1882-1961) An American physicist who studied the properties of matter under extremely high pressure. A graduate of Harvard, he remained there as professor from 1919 rmtil retirement. He was awarded the Nobel Prize for Physics in 1946. He is also noted for his writings on the philosophy of science and studies of electrical conduction in metals and properties of crystals. He was president of the American Physical Society in 1942. 

The temperature dependence of p, can be defined from what is already known about the effect of temperature on phonon activity. If thermal conductivity is used as an index of the phonon effect, Eq. (3.20) gives a 1/T dependence for thermal conductivity. Since thermal conductivity and electrical conductivity in metals are due to the same carriers (electrons), it follows that electrical conductivity will also have a l/T dependence. Since electrical resistance is the reciprocal of electrical conductivity, it follows that p,- will have a linear dependence on T. 

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