Ch12 -...

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Unformatted text preview: **TI89**##BOOKS#############################################R###Ch12###########Z# ####bBEB############H###################################0##### ######################################################### ################ ## CH 12- ELECTRICAL PROPERTIES & 1. (a) Compute the electrical conductivity of a 7.0-mm (0.28-in.) diameter cylindrical silicon specimen 57 mm (2.25 in.) long in which a current of 0.25 A passes in an axial direction. A voltage of 24 V is measured across two probes that are separated by 45 mm (1.75 in.). (b) Compute the resistance over the entire 57 mm (2.25 in.) of the specimen. ( A) sig = conductivity = 1/ro but ro (resistiv) = VA / Il where A = x-sect area so sig = Il/(V*pi*(d/2)^2) s B) ro = RA/l so Resistance = l/(sig*A) = l/(sig*pi*(d/2)^2) ============== 3. (a) Using the data in Table 12.1, compute the resistance of an aluminum wire 5 mm (0.20 in.) in diameter and 5 m (200 in.) long. (b) What would be the current flow if the potential drop across the ends of the wire is 0.04 V? (c) What is the current density? (d) What is the magnitude of the electric field across the ends of the wire? o A) R = ro*l/A = l/(sig*A) = l/(sig*pi*(d/2)^2) B) I = V/R C) J = I/A = I/(pi*(d/2)^2) D) E = V/l ============== 4. How does the electron structure of an isolated atom differ from that of a solid material?------>For an isolated atom, there exist discrete electron energy states (arranged into shells and subshells); each state may be occupied by, at most, two electrons, which must have opposite spins. On the other hand, an electron band structure is found for solid materials; within each band exist closely spaced yet discrete electron states, each of which may be occupied by, at most, two electrons, having opposite spins. The number of electron states in each band will equal the total number of corresponding states contributed by all of the atoms in the solid. n ============== 5. (a) Calculate the drift velocity of electrons in silicon at room temperature and when the magnitude of the electric field is 500 V/m.when the magnitude of the electric field is 500 V/m....
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Ch12 -...

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