Centre for Development of Advanced Computing Electronics-Communication-Engineering-ECE Contributed by Thasni updated on Mar 2019
Placement Paper |   12763

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Electronics and Electrical Objective Questions

 

1. Which of the following pairs does-not match?

(A) Dielectric strength of air 3 to 5 kV/mm

(B) Vacuum may be used for reflective insulation of liquid O2 tank

(C) Permissible water content in transformer oil is 50 ppm

(D) Carbon-pile resistors for insulation of oil-filled cables (Ans)


2. Memory of a computer can be increased by

(A) increasing the magnetic bubble diameter

(B) decreasing the magnetic bubble diameter (Ans)

(C) using adomax, a recent hard magnetic material

(D) using strontium titanate (Sr Ti O3)


3. The residual magnetic flux density is more in

(A) metallic magnets  (Ans)

(B) ceramic magnets

(C) graphite

(D) iron oxide


4. Manganese ferrites is a 1:1 mixture of 

(A) MnO and CdO

(B) MnO and Fe2O3 (Ans)

(C) MnCl2 and Fe2O3

(D) MnCl2 and CdO


5. High frequency transformer cores are generally made of

(A) Cast iron

(B) Mumetal

(C) Ferrite (Ans)

(D) Graphite


6. For high speed reading and storing of information in a computer, the use is made of 

(A) ferrite (Ans)

(B) piezoelectric

(C) pyroelectrics

(D) ferromagnetics above 7680 C


7. The poles of alternators are usually made of

(A) wrought iron

(B) permalloy (Ans)

(C) CdS

(D) alnico


8. In a semi-conductor strain gauge, the change in resistance on application of strain is mainly due to the change in its 

(A) lenght

(B) diameter

(C) resistivity

(D) length and diameter (Ans)

 

9. Transformer oil is a liquid insulator and is mainly used in transformer. It is filled into transformer tank to serve the following purposes:

I. To transfer the heat generated inside the transformer core and windings, to the outer cooling surfaces.

II. To main insulation in the primary and secondary windings.

(A) Only I is correct

(B) Only II is correct

(C) Both I and II are correct (Ans)

(D) None of these


10. Electrons in an atom may be visualized by 

(A) spectroscopic techniques (Ans)

(B) radiography

(C) optical microscope

(D) etching techniques


11. Most malleable metal is 

(A) Au

(B) Ag (Ans)

(C) Cr

(D) Osmium


12. As the temperature of a p-type semi-conductor is gradually and continuously increased, the fermi level will move

(A) into the valence band (Ans)

(B) into the conduction band

(C) towards the middle of the forbidden gap

(D) into the region between the acceptor level and the valence band


13. Which one of the following polarization mechanisms/sets of mechanisms contribute to the static dielectric constant of a homopolar neutral dielectric?

(A) Electronic

(B) Electronic and ionic

(C) Electronic, ionic and dipolar

(D) Electric and dipolar (Ans)


14. Consider the following materials:

1. Pure silica

2. Bakelite

3. Hard rubber

4. Paraffin

The correct sequence of the DECREASING order of loss angles (60 Hz) of these dielectric materials is

(A) 1,2,3,4

(B) 1,4,3,2

(C) 4,1,2,3

(D) 4,3,1,2 (Ans)


15. Which one of the following materials is piezoelectric?

(A) Pb2 Au

(B) BaTiO3 (Ans)

(C) MgAl2O4

(D) NiFe2O4


16.The residual resistivity of metals 

(A) is essentially independent of temperature

(B) increases linearly with increasing temperature (Ans)

(C) decrease linearly with increasing temperature

(D) initially increase linearly with temperature and then remains constant


17. Consider the following metals: 

1. Zinc

2. Gold

3. Silver

4. Copper

The correct sequence of the increasing order of their resistivities is

(A)  4,3,1,2

(B)  3,4,2,1 (Ans)

(C)  4,3,2,1

(D)  3,4,1,2


18. A type-I super-conductor maintained at a temperature T

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