DipIETE – ET (NEW SCHEME)   –   Code: DE54

Subject: ENGINEERING MATERIALS

Time: 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.  Thermocouple work on which of the following effect ?

(A) Thomson effect                               (B) Seaback effect

(C) Pelties effect                                   (D) ) Joule effect

             b. Materials which lack permanent magnetic dipoles are called ?

(A) Diamagnetic                                   (B) Ferromagnetic                                                             

                  (C) Semimagnetic                                 (D) none of the above

             c.  Piezoelectric materials serve as a source of

(A) Micro waves                                  (B) Ultrasonic waves

(C) ) Musical waves                             (D) Resonant waves

             d.  Breakdown in dielectric may be

(A) Electrical breakdown                      (B) Thermal breakdown

(C) Electrochemical breakdown            (D) any of the above

             e.  The number of degree of freedom for monoatomic gas is

(A) 3                                                    (B) 5

(C) 6                                                    (D) 7                                                                    

             f.   A Carbon resistor contains

(A) Solid carbon granules                     (B) Pulverized coal

(C) finally divided carbon black             (D) Carbon crystals

             g. The process by which impurities are added to a pure semi conductor is

(A) Diffusing                                         (B) Drift

(C) Doping                                           (D) Mixing

h.   A semi conductor in its purest form is called ?

(A) Intrinsic Semi conductor                 (B) Extrinsic Semi conductor

(C) P-type Semi conductor                   (D) N-type Semi conductor

             i.   In a transistor which of the following region is very lightly doped and is very thin?

(A) Emitter                                           (B) Base

(C) Collector                                        (D) none of the above

             j.   Thermionic emission of electron is due to

(A) Electromagnetic field                       (B) Electrostatic field

(C) High temperature                            (D) Photoelectric effect

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

  Q.2     a.   Explain the electron gas model of a metal.                                                           (8)

             b.   Explain thermal conductivity of metals. What is the coefficient of thermal conductivity?                    (8)

Q.3     a.   Explain the effect of a dielectric on the behavior of a capacitor.                           (8)

b.   What is permanent dipole moment? Explain in brief.                                            (8)

Q.4     a.   What are the important requirement of good insulating materials? Give some examples & their applications.                                                            (8)

             b.   Explain dielectric properties of polymeric system.                                                (8)

  Q.5     a.   Explain the Process of magnetization of a magnetic material. Draw hysteresis loop for a magnetic material.                                                              (8)

             b.   What are the different factors affecting permeability and hysteresis loss of a magnetic material.                                                                    (8)

Q.6     a.   Describe the Hall effect and explain its relation to the magnetic field on a conductor. Show that the Hall coefficient is equal to (m³/ coulomb)                                                             (8)

             b.   What are the different types of semiconductor? Explain N-type and P-type Semiconductor with the help of energy band diagram.                           (8)

Q.7     a.   What is the difference between Thermisters and Varistors? Describe ‘Thermisters’ in brief.             (8)

             b.   What is Junction Transistors? Describe in brief working of two types of transistors.             (8)

  Q.8     a.   What is wire wound Resistor? Describe different types of wire wound resistors in brief.                  (8)

             b.   What is the function of a relay? How they can be classified in different categories. Explain in brief.                                                              (8)

Q.9     a.   Give general properties of field effect transistor (FET). Mention distinguishing properties of FET from bipolar.                                                                                                          (4+4)

             b.   What are the various methods by which junctions are fabricated from pure single crystal semiconductor?  Describe ‘Grown Junction’ method.                                                                                   (8)