Code: D-04   JUNE / 2003                                            Subject: ENGINEERING MATERIALS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 11 Questions in all.

· Question 1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.

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

Q.1       Choose the correct or best alternative in the following:                                           (2x8)

a. Materials which can store electrical energy are called

(A) magnetic materials.                        (B) semi conductors.

(C) dielectric materials.                        (D) super conductors.

             b.   ACSR (Aluminium Conductor Steel Reinforced) are used as

(A) over head transmission lines.         (B)  super conductors.

(C)  fuse                                              (D)  underground cables.

             c.   Brass is an alloy of

(A) copper and zinc.                           (B)  copper and iron.

(C)  copper and Aluminium.                 (D)  copper and tin.

             d.   Property of material which allows it to be drawn out into wires is

(A) Ductility.                                      (B)  Solder ability.

(C)  Super conductivity.                       (D)  Malleability.

             e.   In n type semi conductor added impurity is

(A) pentavalent.                                  (B)  divalent.

(C)  tetravalent.                                   (D)  trivalent.

             f.    The covers of electrical machines are made of

(A) soft magnetic materials.                 (B)  hard magnetic materials.

(C)  super conductors.                         (D)  semiconductors.                     

             g.   The dielectric constant of air is practically taken as

(A) more than unity.                            (B)  unity. 

(C)  less than unity.                              (D)  zero.

             h.   n-type semiconductor is an example of

(A)  extrinsic semiconductor.                (B)  intrinsic semiconductor.

(C)  super conductor.                          (D)  insulators..

PART I

Answer any THREE Questions. Each question carries 14 marks.

Q.2     a.   Classify plastic materials into two categories, describe their important properties and give two examples of each.                                                   (10)

             b.   Give four examples of natural insulating materials.                                                (4)

Q.3     a.   State the functions of a fuse.  Mention the desirable properties of fuse materials.                  (8)

b. Differentiate between n and p type semiconductors.                                            (6)

Q.4     a.   Explain how materials can be classified into three groups on the basis of atomic structure.                (8)

b.   Discuss briefly :

(i)   Lithography                                   (ii)  Super conductivity.                       (3+3)

Q.5          Describe the physical properties and uses of the following:

(i)   Soft and hard magnetic materials.   (10)

(ii)  Brasses,                                                                                                       (4)

  Q.6           Discuss electrical properties of insulating materials.                                            (14)

PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7           Discuss important properties and uses of

(i) Rubber.                                   (ii)  Mica and Mica products.

(iii) Glass and glass products.         (iv) Ceramics.                                (3.5 x 4)

Q.8     a.   State the advantages and disadvantages of alloying steel with silicon for use as magnetic materials in transformer and electric machines.        (10)

             b.   Describe soldering materials and their uses.                                                         (4)

Q.9           Write short notes on

(i) Soft ferrites and their applications.                                                          (7)

(ii) PVC and its applications.                                                                       (7)

Q.10           a.                                                        What are the desirable properties of an insulation material.   (8)

     b.   Explain dielectric loss and loss angle.    (6)

Q.11                                                                      Explain the following :

      (i)    Permeability.                                (ii)   Dielectric constant.

                   (iii)  Corrosion.                                    (iv)  Contact resistance.                  (3.5 x 4)

JUNE / 2003

Code: D-04             Dec 2003                                       Subject: ENGINEERING MATERIALS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 11 Questions in all.

· Question 1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.

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

Q.1       Choose the correct or best alternative in the following:                                           (2x8)

c. Atomic weight of an atom is

(A) sum of the number of protons and neutrons.

(B) sum of the number of protons and electrons.

(C) sum of the number of electrons and neutrons.

(D) sum of the number of electrons, protons and neutrons.

             b.   An alloy of copper and zinc is

(B) Bronze.                                        (B)  Brass.

(C) Gunmetal.                                      (D)  Nichrome.

             c.   Gold and silver are

(B) dielectric materials

(C) low resistivity conducting materials.

(D) magnetic materials.

(E) insulating materials.

             d.   Phenol and Formaldehyde are polymerised to a resultant product known as

(B) PVC.                                           (B) bakelite.

(C)  polyester.                                     (D) teflon.

             e.   Hard Ferrites are used for making

(B) transformer cores.                        (B)  electrical machinery.

(C)  high frequency equipment.             (D)  light weight permanent magnets.

             f.    Thermocouples are used for the measurement of

(B) humidity.                                      (B)  pressure.

(C)  temperature.                                 (D)  density.                      

             g.   Large scale integration chips have between

(A) Less than 10 components.            (B) 10 and 100 components.

(C)  100 and 1000 components.          (D)  More than 1000 components.

             h.   All semiconductors in their last orbit have

(A)  8 electrons.                                  (B)  2 electrons.

(C)  4 electrons.                                  (D)  6 electrons.

PART I

Answer any THREE Questions. Each question carries 14 marks.

Q.2     a.   With the help of energy bands explain how conduction takes place in conductors, semiconductors and insulators.                                            (9)

             b.   Write a note on superconductors.                                                                       (5)

Q.3     a.   Classify the conducting materials. Describe their properties.                              (10)

d. An electric heater element is made of Nichrome wire having resistivity equal to ohm-metre. The diameter of the wire is 0.3 mm. Calculate the length of the wire required to get a resistance of 30 ohms.                                                           (4)

Q.4           Explain in detail the electrical properties of insulating materials.                          (14)

Q.5     a.  Classify the different types of insulating materials with reference to their limiting safe temperatures for use.                                                               (8)

      b.  Explain the chemical properties of insulating materials.                                         (6)

  Q.6     a.   What are plastics? Give their classification and also the differences between them.               (2+2+4)

             b.  Give the properties and applications of

                   (i)  Teflon

(ii) Bakelite                                                                                                    (3+3)

PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7     a.   Distinguish between ferromagnetic, paramagnetic and diamagnetic materials, mentioning at least one example of each.                                               (9)

b.   What are hard magnetic materials? Name the various magnetically hard alloys.                    (5)

Q.8           Give the properties and application of brass and bronze, asbestos and glass.     (14)

Q.9     a.   What is the effect of temperature on conductivity of semiconductor?                    (6)

b.   Explain the atomic structure and energy band diagram of the most commonly used semi-conducting materials.                                                           (8)

Q.10           a.                                                        Name the materials used in the following cases. Give reasons in each case.

(i) Fuses.

(ii) Solder.

(iii) Bimetals.                                                                                       (3+3+3)

     b.   Explain the principle of a thermocouple. Give two examples of some common thermocouples.                                                                    (5)

Q.11                                                                      Write notes on any TWO

(i) pnp transistors.

(ii) Hysteresis loop.

(iii) Factors affecting the resistivity of conducting materials.

(iv) Applications and properties of aluminium and copper.                         (7+7)

DEC./2003

Code: D-04    Jun 2004                                                 Subject: ENGINEERING MATERIALS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 11 Questions in all.

· Question 1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.

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

Q.1       Choose the correct or best alternative in the following:                                           (2x8)

e. The material with lowest resistivety is

(A) constantan.                                    (B) silver.

(C) manganin.                                      (D) nichrome.

             b.   The property due to which the resistance of some metal or compound vanishes under certain conditions is

(C) Semi conductivity.                        (B)  Super conductivity.

(C)  Curie point.                                  (D)  Magnetostriction.

             c.   Bronze is an alloy of

(F) copper.                                        (B)  aluminium.

(C)  silver.                                           (D)  carbon.

             d.   Ceramics are good

(C) insulators.                                     (B) conductors.

(C)  superconductors.                          (D) semiconductors.

             e.   The materials used for storing electric energy are

(C) dielectrics.                                    (B)  semiconductors.

(C)  superconductors.                          (D)  thermistors.

             f.    The critical temperature above which the ferromagnetic materials loose their magnetic property is known as

(C) hysterisis.                                     (B)  Curie point.

(C)  transition temperature.                  (D)  standard temperature.            

             g.   Permanent magnets are made of

(A) soft magnetic materials.                 (B) hard magnetic materials.

(C)  semi conductors.                          (D)  super conductors.

             h.   Holes are majority carriers in

(A)  P-type semiconductors.                (B)  N-type semiconductors.

(C)  Insulators.                                    (D)  Superconductors.

PART I

Answer any THREE Questions. Each question carries 14 marks.

Q.2     a.   Differentiate between conductors semiconductors and insulators.  Give two examples of each.                                                                   (10)

             b.   Discuss the advantages and disadvantages of aluminium as compared to copper as a conductor of electricity.                                                                                                                        (4)

Q.3     a.   Differentiate between thermosetting and thermoplastic materials.  Give two examples of each.                                                                    (8)

f. Explain

(i)   Superconductivity.                         (ii)   Resistivity.                                       (6)

Q.4     a.   Discuss electrical properties of insulating materials.                                            (10)

             b.   What is the effect of overheating on the life of an electric insulator?                      (4)

Q.5          Write notes on

(i) Brass and Bronze.                   (ii)  Thermocouples.

(iii) P-N junction.                           (iv)  Fuse materials.                (3.5 x 4 = 14)

  Q.6           Discuss classification of insulating materials on the basis of physical and chemical structure.              (14)

PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7     a.   Draw the hysteresis loop for a soft magnetic material and compare it with the hysteresis loop of hard magnetic material.  Give two examples of each.                                                 (10)

b.   Write a note on

                   (i)    Corrosion.                                    (ii)  Bimetals.                                           (4)

Q.8     a.   Give a short description of soft ferrites. (5)

b.   Explain

(i)   Eddy currents.                               (ii)   Magnetostriction.

                   (iii) Permeability.                                                                                          (3 x 3)

Q.9     a.   Differentiate between diamagnetic paramagnetic and ferromagnetic materials.                      (9)

b.   Write a note on soldering materials.                                                                    (5)

Q.10                                                                      Discuss properties and uses of

(iv) Mica and mica products.          (ii)  Teflon.

(iii)      Rubber.                                    (iv)  Asbestos.                       (3.5 x 4 = 14)

Q.11                                                                      Discuss the properties and uses of

(v) Cold rolled grain oriented steel.                                                              (7)

(vi) ALNICO.                                                                                             (7)

JUNE/2004

Code: D-04   Dec 2004                                                 Subject: ENGINEERING MATERIALS

Time: 3 Hours                                                                                                      Max. Marks: 100

NOTE: There are 11 Questions in all.

· Question 1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.

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

Q.1       Choose the correct or best alternative in the following:                                           (2x8)

g. Materials, which provide a path to the magnetic flux, are classified as

(A) insulating materials.                        (B) semi conducting materials.

(C) magnetic materials.                        (D) dielectric materials.

             b.   Germanium possesses

(D) one valence electrons.                  (B) two valence electrons.

(C)  three valence electrons.                 (D) four valence electrons.

             c.   Dielectric constant of vacuum is

(G) infinity.                                         (B)  100.

(C)  one.                                             (D)  zero.

             d.   Ferrites are

(D) ferromagnetic material.                 (B) ferrimagnetic materials.

(C)  anti ferromagnetic material.           (D) diamagnetic materials.

             e.   Thermocouples are used for measuring

(D) current.                                        (B)  voltage.

(C)  temperature.                                 (D)  pressure.

             f.    The relative permeability of a paramagnetic substance is

(D) unity.                                            (B)  slightly more than unity.

(C)  zero.                                            (D)  less than unity.            

             g.   Hall effect may be used for which of the following?

(B) determining whether the semiconductor is p or n type.

(C) determining the carrier concentration.

(D) calculating the mobility.                

(E) All the above.

             h.   Manganin is an alloy of

(A)  copper, manganese and nickel.     (B)  copper and manganese.

(C)  manganese and nickel.                  (D)  manganese, aluminium and nickel.

PART I

Answer any THREE Questions. Each question carries 14 marks.

Q.2     a.   Explain the factors which change the resistivity of a conducting material               (8)

             b.   A heater element is made of nichrome wire having resistivity equal to  ohm-m.   The diameter of the wire is 0.4mm.  Calculate the length of the wire required to get a resistance of 40 .    (6)

Q.3     a.   Explain superconductivity and explain the effect of magnetic field on superconductors.                     (6)

h. Give the properties and application of copper and aluminium.                              (8)

Q.4     a.   What is polarisation?  Explain.                                                                            (6)

             b.   Give the properties and application of glass and cotton.                                       (8)

Q.5     a.   Give the names of four alloys along with their composition, which are used for making heater and thermocouple elements.                        (6)

b.   Explain ferroelectricity and piezoelectricity.                                                         (8)

  Q.6     a.   Explain the electrical contact materials with examples.                                         (7)

b.   Explain the terms dielectric constant and dielectric loss angle.                              (7)

PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7     a.   Explain the effect of temperature on the conductivity of a semiconductor.             (8)

b.   Explain n-type and p-type semiconductors.                                                         (6)

Q.8           Differentiate between diamagnetic, paramagnetic, ferromagnetic and ferrimagnetic materials and give examples of each.                                (14)

Q.9     a.   Give the properties and uses of silicon iron alloy and nickel iron alloy.                  (6)

b.   Explain the working of an npn transistor.                                                             (8)

Q.10           a.                                                        What is meant by doping?  How does it affect a semiconductor?                                                           (6)

b.   Explain the factors affecting permeability and hysterisis loss.                                (8)

Q.11                                                                      Write notes on

(vii) Classification of materials on the basis of energy band.                            (7)

(viii) Germanium and silicon.                                                                          (7)