No. of Printed Pages: 3 IOIEE-002 1
DIPLOMA IN ELECTRICAL ENGINEERING
(DELVI)
Term-End Examination

00376
June, 2016
OIEE-002 ELECTRICAL ENGINEERING MATERIALS
Time hours Maximum Marks: 70
Note: Attempt any five questions. All questions carry equal marks. Use of scientific calculator is allowed.

1. Name any two factors responsible for decay in an insulating system.

Define relaxation time in case of movement of electrons in a conductive material.

Define second ionization coefficient in dielectric breakdown in gases.

Give any two properties of a ferromagnetic material.

Name any two theories used to explain the dielectric breakdown of solids.

State what do you mean by superconductivity.

What is the difference between a dielectric and an insulator? 7x2=14

2. Define and explain relaxation time, collision time and mean free path of electrons in a conductive material. 7

Explain how heat is developed in a current carrying conductor and define thermal conductivity of metals. 4 3

3. With the help of a neat diagram, explain the dielectric breakdown in liquids, according to colloidal theory. 7

Define secondary ionization coefficient and explain Townsend's criterion with the help of a neat sketch and suitable expressions. 2 5

4. What are the various factors that influence the characteristics of an insulating system? Discuss them in brief. 7

Explain ionic polarization as a function of frequency. Define the term ionic polarization. 5 2

5. Compare paramagnetic materials with ferromagnetic materials. Draw and explain a typical hysteresis curve for a ferromagnetic material. 4 3

Give a detailed classification of magnetic materials and discuss the origin of permanent magnetic dipole. 5 2

6. Explain the thermal discharge breakdown of a solid dielectric material with the help of a suitable diagram. 7

Explain magnetic resonance and its significance with the help of a suitable sketch.

7. Write short notes on any two of the following: 2x7=14
Energy Band Description Dielectric Losses Insulation Measurement