AMIETE – ET (NEW SCHEME)   –   Code: AE58

 

Subject: MATERIAL AND PROCESSES

Flowchart: Alternate Process: DECEMBER 2009Time: 3 Hours                                                                                                     Max. Marks: 100

 

 

 

 

NOTE: There are 9 Questions in all.

·      Question 1 is compulsory and carries 20 marks. Answer to Q.1  must be written in the space provided for it in the answer book supplied and nowhere else.

·      Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

·      Any required data not explicitly given, may be suitably assumed and stated.

 

 

Q.1       Choose the correct or the best alternative in the following:                                  (210)

       

             a.  The crystal structure for iron is  

 

                  (A) F.C.C                                            (B) B.C.C.                                                                                    

                  (C) H.C.P                                            (D) COMPLEX                                                   

 

             b.  In Graphite the bonding is

                 

                  (A) Covalent                                        (B) Metallic

                  (C) van der Waals                                (D) van der Waals and Covalent

 

             c.  The conductivity of a conductor can be increased by

                

                  (A) decreasing its temperature               (B) increasing its temperature

                  (C) decreasing its vibration                    (D) increasing its vibration

 

             d.  The transition from superconducting state to conducting state

 

                  (A) irreversible                                     (B) reversible

                  (C) both                                               (D) none

 

             e.  Polarization is

                                                                              (A) a scalar quantity               (B) a vector quantity

 (C) both                                                (D) none of the above

 

             f.   Piezoelectric materials serve as a source of

 

                  (A) resonant waves                               (B) musical waves

                  (C) microwaves                                    (D) ultrasonic waves

 

             g. If a magnetic material has permanent dipoles and the interaction

                 between neighboring dipoles is described by anti-parallel

                  orientation of unequal moments, the material must be   

 

                  (A) diamagnetic                                    (B) paramagnetic

                  (C) ferromagnetic                                 (D) ferrimagnetic

            

             h.  The forbidden energy gap in semiconductor

 

(A)  lies just below the valence band

(B) lies just above the conduction band

                  (C) lies in between the conduction band and valence band

                  (D) is the same as the valence band

 

             i.   By increasing the impurity contents in the metal alloy the residual resistivity always

 

                  (A) Decreases                                     

                  (B) increases

                  (C) remains constant                            

                  (D) Becomes temperature interdependent

 

             j.   The main constituent of glass is

 

                  (A)                                             (B)                                                             

                  (C)                                            (D) none of these

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

 

  Q.2     a.   The density of potassium, which has the BCC structure and one atom per lattice point, is 0.855 g/cm3. The atomic weight of potassium is 39.09 g/mol. Calculate                                                          (8)

                   (i)   the lattice parameter; and                                                                                      

                   (ii)  the atomic radius of potassium.

                                                                                                                                                

             b.   Describe in detail the ionic, covalent and metallic bonds observed in materials. Give one example of each.                                                              (8)

            

  Q.3     a.   Explain single crystal, polycrystalline material and non-crystalline material(8)

 

             b.   If electroneutrality is to be preserved, what point defects are possible in NaCl when a Ca2+ substitutes for a Na+ ion? How many of these defects exist for every Ca2+ ion?                                            (4)

 

             c.   The density of a sample of FCC palladium is 11.98 gm/cm3 and its lattice parameter is 3.8902 . Calculate the fraction of the lattice points that contain vacancies. Mass of Pd per mole is 106.4 gm. (4)

 

  Q.4     a.   Explain the difference between self-diffusion and inter-diffusion.                          (4)

                  

             b.   Derive the formula for electrical conductivity in metals and show that the conductivity is proportional to the density of free electrons and to the electron mobility.                                                         (6)

 

             c.   How do the electrical and mechanical properties of copper compare with that of aluminium, for use as conductor?                                                                                                        (6)

 

  Q.5     a.   Explain the phenomena of polarization in dielectric materials. What is dielectric breakdown?                                                                       (8)

 

             b.   What are the characteristics of ferroelectric materials? Name some important ferroelectric materials.                                                                      (8)

 

  Q.6     a.   For Nickel, which has a density of 8.90 g/cm3, the mass per mole                 ANi = 58.71 g/mole and, the number of Bohr magnetons per atom  is 0.60 . Calculate                                                    (8)

                   (i)  the saturation magnetization and

                   (ii) the saturation flux density.

 

             b.   Explain the term Magnetostriction as applied to ferromagnetic materials. What are its applications?                                                             (8)

       

Q.7       a.    Show that in an intrinsic semiconductor, the Fermi level lies midway between the conduction and valence bands.                                                                                                               (8)

 

             b.   What is Hall Effect? Derive a relation between Hall coefficient and carrier density.              (8)

 

  Q.8     a.   Explain why two separate BJTs cannot be connected to make a p-n-p-n switch? How does gate bias provide switching in an SCR?               (8)

 

      b.   Explain the construction of Mica and Ceramic capacitors.                               (4+4)

                                                 

Q.9       a.   What are alloy junction transistor? Why they were replaced by planar transistor?                (6)

               

             b.   Write short notes on:                                                                                        (10)

                                                                                                                                                

                   (i)  Czochralski method

                   (ii) Zone-refining.