Electrical resistivity of metals

Concept Check 18.1 If a metallic material is cooled through its melting temperature at an extremely rapid rate, it forms a noncrystalline solid (i.e., a metallic glass). Will the electrical conductivity of the noncrystalline metal be greater or less than its crystalline counterpart  

As mentioned previously, most metals are extremely good conductors of electricity room-temperature conductivities for several of the more common metals are given in Table 18.1. (Table B.9 in Appendix B lists the electrical resistivities of a large number of 

Room-Temperature Electrical Conductivities for Nine Common Metals and Alloys 

FigMre 18.8 The electrical resistivity versus temperature for copper and three copper-nickel alloys, one of which has been deformed. Thermal, impurity, and deformation contributions to the resistivity are indicated at -100°C. 

Matthiessen s rule— for a metal, total electrical resistivity equals the sum of thermal, impurity, and deformation contributions Matthiessen s rule 

---

The main contributions to the electrical resistivity of metals, p, consists of an intrinsic temperature-sensitive ideal term, p,-, which is mainly due to electron-... 

P.L. Rossiter, The Electrical Resistivity of Metals and Alloys," Cambridge Univ. Press, Cambridge (1987). 

G.T. Meaden Electrical resistance of metals, Heywood, London (1966)... 

The resistance thermometry is based on the temperature dependence of the electric resistance of metals, semiconductors and other resistive materials. This is the most diffused type of low-temperature thermometry sensors are usually commercial low-cost components. At very low temperatures, however, several drawbacks take place such as the low thermal conductivity in the bulk of the resistance and at the contact surface, the heating due to RF pick up and overheating (see Section 9.6.3)... 

The electric resistance of metals decreases as temperature is lowered down to about 20 K. The most used metal as thermometric material is platinum. Platinum is chemically resistant and can be produced with high purity (minimizing the temperature-independent... 

Pe — Electrical resistivity of metal Pm — Density of liquid metal at T... 

The phenomenon of superconductivity was discovered at the beginning of the twentieth century by the Dutch physicist H. Kamerlingh Onnes, during the first attempts to liquefy helium (which at atmospheric pressure boils at 4.2 K). After refining the technique of helium liquefaction, in 1911, Onnes attempted to measure the electrical resistance of metals at these extraordinary low temperatures, and realized that at 4 K the resistance of mercury, as well as that of other metals indicated in Figure 1, became too low to be measured. This change in electrical property became the indication of the new superconductive physical state. The temperature below which materials become superconducting is defined as the critical temperature, Tc. 

In the sense of electric conductivity, semiconductors are close to conductors but have very few free electrons. When electric resistance of metals increases with temperature, the semiconductor resistance decreases with temperature. Some of the electrons that are not free at normal temperature... 

The resistance overpotential of the cell IR is mainly a function of the solution conductivity of the electrolyte and the distance between the electrodes since the electrolytic resistivity is far more important than the electric resistance of metals. 

These values were obtained by fitting all available measurements to a theoretical formulation describing the temperature and composition dependence of the electrical resistivity of metals. Some of the values listed here fall in regions of temperature and composition where no actual measurements exist. Details of the procedure may be found in the reference. 

Thermoelectric Refrigeration, 1964 Electrical Resistance of Metals 1965 Specific Heats at Low Temperatures, 1966 Safety with Cryogenic Fluids, 1967... 

Resistance temperature detectors (RTDs) indicate temperature values according to changes in the electrical resistance of metals. 

Electrical Conductivity of Metals Electrical Resistivity of Metals Electrical Resistivity of Alloy Cast Irons Resistivity of Ceramics Volume Resistivity of Glass Volume Resistivity of Polymers... 

Rossiter, P. (1991). The electrical resistivity of metals and alloys. Cambridge Univ Pr. 

The electrical resistance of metals is of the order of 10 Q cm, whereas that of a typical insulator would be 10 ft cm. The electrical resistance of natural fibres is governed by the humidity of the air to which they are exposed (Murphy and Walker, 1928). For example, the specific resistance of wool varies from 1.6 x lO Qcm at 53% relative humidity (RH) to 1.3 x 10 at 86% RH (Marsh and Earp, 1933). In contrast, the resistance of polyester at 85% RH is greater than 7 x 10 Q cm (Hersh and Montgomery, 1952). At normal temperatures, the resistance of metals is proportional to the absolute temperature, whereas the resistance of insulators increases as temperatures decrease (Bardeen, 1940). The electrical conductivity of copper, silver and gold at 0 °C are 64, 66 and 49 x 10 " cm respectively (Bardeen, 1940). 

---