课程名称︰材料科学导论 课程性质︰ 系定必修/外系选修 课程教师︰郭博成 开课学院︰工学院 开课系所︰材料系 考试日期（年月日）︰2009/06/16 考试时限（分钟）：80 mins (开讲义＆课本) 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : [1] Briefly describe (a) the origins of the magnetic moment of an atom. (b) the differences among diamagnetism, paramagnetism, ferromagnetism, antiferromagnetism, and ferrimagnetism. (15%) [2] Why the magnetic moment of an atom in the magnetic material will orient to the applied magnetic field direction if the magnetic field is large enough? (10%) [3] Illustrate the boundry in T-H-J (temperature-magnetic field-current density ) space separating superconducting states and normal states. (10%) [4] Schematically sketch on a single plot the M-versus-H behavior for a ferromagnetic material (a) at 0 K, (b) at a temperature just below its Curie temperature, and (c) at a temperature just above its Curie temperature. Brief;y explain why these curves have different shapes. (15%) [5] Explain why the resistivity of metal is increased with temperature but the resistivity of intrinsic semiconductor is decreases with increasing temperature. (10%) [6] How does the electron structure of an isolated atom differ from that of a solid material? (10%) [7] Some hypothetical metal is known to have an electrical resistivity of 4x10^-8(Ω-m). Through a specimen of this metal that is 25mm thick is passed a current of 30A; when a magnetic field of 0.75 tesla is simultaneously imposed in a direction perpendicular to that of the current, a Hall voltage of -1.26x10^-7V is measured. Compute (a)the electron mobility for this metal, and (b)the number of free electrons per cubic meter. (10%) [8] Zinc telluride has a band gap of 2.26eV. Over what range of wavelengths of visible light is it transparent? (The wavelengths of visible light are between 0.4μm and 0.7μm. The Plank's constant h=4.13x10^-15eV-s) (10%) [9] Briefly explain what determines the characteristic color of (1)a metal and (2)a transparent nonmetal. --

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