[試題] 95下 郭博成 材料科學導論 期末考

[raye2928 (raye)]

課程名稱︰材料科學導論

課程性質︰必修

課程教師︰郭博成

開課學院：工學院

開課系所︰材料系

考試日期（年月日）︰6/26

考試時限（分鐘）：120Mins

是否需發放獎勵金：是的  謝謝

（如未明確表示，則不予發放）


試題 :

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. Schematically sketch on a single plot the B-verusH behavior for a
   ferromagnetic materials (a) at 0 K , (b) at a temperature just below its
   Curie temperature, and (c) at a temperature just above its Curie
   temperature. Briefly explain why these curves have different shape. (10%)

3. For a superconducting material at a temperature T below the critical
   temperature Tc, the critical field Hc(T), depends on temperature according
   to the relationship
       Hc(T) = Hc(0) (1-T^2/Tc^2)
   where Hc(0) is the critical field at 0 K.
   (a) Using the data in table 21.7, calculate magnetic fields for tin at 1.5
       and 2.5 K

   (b) To what temperature must lead be cooled in a magnetic field of 20,000
       A/m. For it to be superconductive.  10%

4.(a) Compute the number of free electrons and holes that exist in intrisic
      germanium at room temperature, using the data in Table 19.2.

  (b) Explain the difference. You will need the densities for Ge and Si, which
      are 5.32 and 2.33 g/cm^3 ,re-spectively.  15%

5. Describe the  differences between the conductivities of intrinsic
   semiconductor and extrinsic semiconductor.  10%

6. Some hypothetical metal is known to have an electrical resistivity of
   4*10^-8 (歐姆-m). through a specimen of this mental that is 25mm thick is
   passed a current of 30 A ; when a magnetic field of 0.75 tesla is
   simultaneously imposed in a direction perpendicular to to that of the
   current, Hall votage of -1.26*10^-7 V is measured. Compute
   (a) the electron mobility for this metal, and
   (b) the number of free electrons per cubic meter. 10%

7.(a) Briefly explain why the ferroelectric behavior of BaTiO3 cease above
      its ferroelectric Curie temperature.
  (b) Would you expect the pysical dimensions of a piezoelectric material
      such as BaTiO3 to change when it is subjected to an electron field? Why
      or why not?  10%

8. Zinc telluridehas a band gap of 2.26 eV. Over what range of wavelengths of
   visible light isit transparent?  10%

9. Briefly explain determines the characteristic color of (1) a metal and (2)
   a trans parent nonmetal. 10%

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