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Unformatted text preview: IE 320 - Spring 2003 Homework Ch. 12 Introduction to Materials Science
12.1 (a) Compute the electrical conductivity of a 5.1-mm (0.2-in.) diameter cylindrical silicon specimen 51 mm (2 in.) long in which a current of 0.1 A passes in an axial direction. A voltage of 12.5 V is measured across two probes that are separated by 38 mm (1.5 in.). (b) Compute the resistance over the entire 51 mm (2 in.) of the specimen. 12.4 Demonstrate that the two Ohm’s law expressions, Equations 12.1 and 12.5, are equivalent. 12.10 Briefly tell what is meant by the drift velocityand mobility of a free electron. 12.10 a) Calculate the number of free electrons per cubic meter for gold assuming that there are 1.5 free electrons per gold atom. The electrical conductivity and density for Au are 4.3 x107 (Ω -m)-1 and 19.32 g/cm3, respectively. (b) Now compute the electron mobilityfor Au.
2 1 IE 320 - Spring 2003 Introduction to Materials Science
12.17 Determine the electrical conductivity of a Cu-Ni alloy that has a yield strength of 125 MPa (18,000 psi). You will find Figure 8.16b helpful. 12.23 Define the following terms as they pertain to semiconducting materials: intrinsic, extrinsic, compound, elemental. Now provide an example of each. 12.31 Using the data in Table 12.2, compute the electron and hole concentrations for intrinsic InSb at room temperature.. 12.34 Compare the temperature dependence of the conductivity for metals and intrinsic semiconductors. Briefly explain the difference in behavior. 12.41 Estimate the temperature at which GaAs has an electrical conductivity of 3.7x10-3 (Ω -m)-1 assuming the temperature dependence for σ of Equation 12.39a. The data shown in Table 12.2 might prove helpful.
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