The charge carriers in metals are the electrons in

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Unformatted text preview: book Table of Contents eutectoid reaction The transfor of a solid phase isothermally and solid phases. pg038 [V] G2 7-27060 / IRWIN / Schaffer Part I Fundamentals Next we consider the response of a solid to an applied electric field. Electrical conduction involves the directed motion of charges in response to an applied field. The electrical conductivity of materials depends on three factors: (1) the type of charge carrier in the materials (electrons or ions), (2) the spatial density of charge carriers, and (3) the charge carrier mobility, or ease with which the charge carriers can move through the atomic scale structure of the material. The charge carriers in metals are the electrons in the cloud that surrounds the atomic cores. In part because of their small size, the loosely bound or free electrons can move relatively unimpeded through the metal, resulting in a high chargecarrier mobility. The combination of high mobility and high concentration of charge carriers leads to high electrical conductivities for most metals. In contrast, each ion in an ionic solid has a filled valence shell. Hence, none of the electrons can be easily removed from its host ion. Instead, charge motion and, hence, electrical conduction often require movement of entire ions. Since such motion is comparatively difficult and slow, and the density of mobile ions is considerably less than the density of mobile electrons in metals, ionic solids are generally characterized as electrical insulators rather than electrical conductors. ....................................................................................................................................... DESIGN EXAMPLE 2.4–5 Electric utility companies must transport electricity from the power generation plant to consumers. As shown in Figure 2.4–6, one of the common transmission methods is to use above-ground wires suspended between structural support towers. The towers and transmission wire are often fabricated from metals, but the “space...
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This note was uploaded on 02/25/2013 for the course PHYS 2202 taught by Professor Sowell during the Spring '10 term at Georgia Institute of Technology.

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