Electrical Engineering Materials Question Paper of 3rd Semester Electrical(D) Download Previous Years Question Paper 2

S.B. Roll No.______

ELECTRICAL ENGINEERING MATERIALS

3^rd Exam/Elect/5208/Dec’05

Duration: 3 hrs.

1.                 Choose the correct one

a.                 Resistivity of copper at absolute zero is

i.                        1.56 µ ohm-cm

ii.                        3.12 µ ohm-cm

iii.                        6.62 µ ohm-cm

iv.                        Negligibly small

b.                 Insulating material used in spark plugs is

i.                        Rubber

ii.                        Porcelain

iii.                        Mica

iv.                        Polystyrene

c.                  The permeability of iron can be increased by

i.                        Purifying it

ii.                        Reducing carbon percentage

iii.                        Increasing carbon percentage

iv.                        Afoying with cobalt

d.                 Which of the following is not the characteristics of glass

i.                        Brittle and hard

ii.                        High chemical resistance

iii.                        Electrodes of thermionic valves

iv.                        Pressure sensitive element

State true or false

a)                 Resistivity of insulators ranges form 109 to 1018 ohm-cm

b)             Magnetostriction is the changes in dimensions of a Ferro-magnetic substance due to 

          magnetization.

c)                 The variation of resistance of a semi conductor with temperature is linear.

d)                Silicon steels used for electrical purposes have silicon percentage 2.5%

e)                 The crystal structure of most of the common metal is cubic

Note: Attempt any five questions

2.                  

a.                 Explain the following terms:

i.                        Valence electrons

ii.                        Band gap

b.                 What do you mean by temperature coefficient of resistance? Explain

c.                  What are different applications of superconductors?

d.                 Explain the following:

i.                        Hygrocoplicity

ii.                          Heat resistance

e.                  What do mean by doping? Explain

f.                   Sketch the B-H loop of a typical ferromagnetic material and define the coactivity.

g.                 Discuss the properties of platinum.

h.                 What do you mean by thermocouple? Explain.

Section –C

          Note: Attempt any three questions

3.                 Explain the following:

a.                 Insulator

b.                 Semi conductor

c.                  Conductor

4.                 Discus properties and applications of following material.

a.                 Nitrogen

b.                 Cotton

5.                 Discuss properties and applications of following hard magnetic material.

a.                 Tungsten steel

b.                 Cobalt steel

6.                  

a.                 Thermosetting plastics

b.                 Ferromagnetic material

7.                 Describe the properties and application of following material.

a.                 Aluminlum

b.                 Porcelain