Tuesday, September 6, 2016
- Tuesday, September 06, 2016
- PunjabtechnicalUniversity ajay gour
- 3rd Semester Electrical(D), Electrical Engineering Materials Electrical(D) 3rd
- No comments
S.B. Roll No.______
ELECTRICAL ENGINEERING MATERIALS
Duration: 3 hrs.
1. Fill in the blanks
a. The electrical class fiction of materials is based upon _____
b. Filament of lamps is made of _________
c. Low resistivity materials have __________ value of conductivity.
d. In N- type semiconductors, the minority carriers are ______
e. A pure semiconductor is called_______
f. ___________ is employed for cable insulation.
g. A good insulating materials should have ________ dielectric strength.
h. Area of hysteresis loop ________
i. Fuse is always connected in ______ with the electric and electronic circuit.
j. The materials used for making brushes of a DC machine is made of _____
2. Attempt any six questions.
a. Although silver is best known conductor, yet we prefer copper and aluminum, why?
b. What is resistance? On what factors does it depend? How it is affected by temperature?
c. Explain the effect of alloying on resistivity with examples.
d. Why the temperature coefficient of resistance of a semiconductor is negative? Explain.
e. Write down some important applications of following:
f. What are the various thermal properties of insulating materials?
g. What are soft and hard magnetic materials?
h. Fuse material should have low melting point, why?
Note: Attempt any three questions
a. Explain the following terms:
i. Valence electrons
ii. Band gap
b. What are superconducting materials?
a. What are the major alloys of copper?
b. Differentiate between intrinsic and extrinsic semiconductors.
5. Mention a few applications of the following natural insulating materials:
6. Write the short note on
a. Thermosetting plastics
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