As the temperature increases, the conductivity of a metaldoes not increase because of the increased diffusion of the atomsdoes not decrease because of the decrease in the number of free electronsdoes not increase due to the increased mobility of electrons and holesdecreases because of increased electron scatteringWith respect to the band model of conductionenergy gaps exist in the band structure of solids as remnants of the discrete energy levels of electrons in atomsconduction in metals does not only occur in the conduction bandneither insulators nor semiconductors conduct electricity at zero Kelvinelectrons are not promoted from the conduction band to the valence band via thermal energyWhich of the following parameters affect the conductivity of intrinsic semiconductorssize of the band gapnot concentration of dopantstemperatureValence band hole concentrationIn extrinsic semiconductors, which of the following are trueFalse - The average valence of the atoms can be 3, 4, or 5False - there is a saturation region for n-type semiconductors at low temperatureTrue - at high temperatures there is no difference in conductivity vs. the intrinsic behaviorTrue - the mobility of the electrons are decreased at higher dopant concentrationStressis not force over original lengthis not elongation over the original lengthhas SI units of Pais less for a material with a larger cross-sectional area for a given forceWhich of the following are elastic properties of a material?Young's modulusnot elongation to failurePoisson's ratioShear ModulusDuring plastic deformationdislocations do not move in amorphous polymersthe cross-sectional area does not stay constantpermanent changes in dimension occurFalse - the ultimate tensile strength must have been exceededWhich of the following are properties describing the plastic behavior of materialsDuctilityyield strengthtensile strengthtoughnessSlipDoes not occur via the movement of vacanciesDoes not occur equally easily on any crystallographic plane in any crystallographic directionDoes not occur in amorphous polymersis responsible for plastic deformation in metalsIn polycrystalline metallic materialsyield is more difficult than in single crystalsslip occurs on the planes that are most favorably oriented with respect to the applied force axisgrains do not retain their shape during plastic deformationgrain boundaries increase the yield strengthThe following are strengthening mechanismssmall grain sizesadding solutecold workFalse - annealingTo reset the the microstructural and mechanical characteristics of a metal, which of the following can occur during the heat treatment?relief of the stored internal strain energy by dislocation motionrecrystallizationFalse - grain elongationdecrease in tensile strengthFractureDoes not always occurs at the yield strength (or elastic limit)can occur at stresses less than the yield strengthcan occur in a brittle mannercan occur in highly ductile metals via up-and-cone formationFracture toughnessis a material property, it describes the driving force for fracturedescribes a material's resistance to brittle fracture when a crack or other defect is presentis not a function of the flaw sizeis not a function of the applied stress levelDuring fatiguethe applied stress varies with timehigher mean stress levels decrease fatigue lifecracks do not normally nucleate under the surfacebeachmarks and striations often form on the fracture surfaceCreep occursFalse - for all materials above 0.2 of their melting temperature when expressed in deg Cin three stages: primary, secondary and tertiaryfaster at higher stressFalse - faster at lower