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MAP821S - MATERIALS PHYSICS - 1ST OPP- NOV 2022 |
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nAmlBIA UnlVERSITY
OF SCIEnCE Ano TECHnOLOGY
FACULTYOF HEALTH,NATURALRESOURCESAND APPLIEDSCIENCES
DEPARTMENT OF NATURALAND APPLIEDSCIENCES
QUALIFICATION: BACHELOROF SCIENCEHONOURS
QUALIFICATION CODE: 08BOSH
LEVEL: 8
COURSECODE: MAP821S
COURSENAME: MATERIALSPHYSICS
SESSION:NOVEMBER 2022
DURATION: 3 HOURS
PAPER:THEORY
MARKS: 100
FIRSTOPPORTUNITY EXAMINATION QUESTION PAPER
EXAMINER(S) Prof Dipti R. Sahu
MODERATOR: Dr Zivayi Chiguvare
INSTRUCTIONS
1. Answer all five questions.
2. Write clearly and neatly.
3. Number the answers clearly.
PERMISSIBLEMATERIALS
Non-programmable Calculators
THIS QUESTION PAPERCONSISTSOF 3 PAGES(Including this front page)
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Question 1
[10)
1.1 What is the difference between engineering stress and true stress in a tensile test?
(2)
1.2 A cylindrical specimen ofa nickel alloy having an elastic modulus of207 GPa and (4)
an original diameter of 10.2 mm will experience only elastic deformation when a tensile
load of 8900 N is applied. Compute the maximum length of the specimen before
deformation if the maximum allowable elongation is 0.25 mm.
1.3 How are the different materials classified?
(4)
Question 2
[10)
2.1 Why are metals transparent to high-frequency X-ray and y-ray radiation?
(2)
2.2 Ifa filter material has an absorption coefficient, a= l20m· 1 for a given wavelength, how (4)
thick should the filter be for it to show a transmittance of 50%? (Assume that reflection
losses at the front and rear faces are negligible, and that incidence is perpendicular).
Determine the attenuation of this filter.
2.3 What is an optical fiber? Explain different types of optical fibres?
(4)
Question 3
[101
3.1 Define thermal stresses and mention the nature of stress if the materials are heated
(2)
3.2 How much energy does the freezer has to remove from 1.5 kg of water at 20° C to make (4)
ice at - l 0°C? (Given, Swate=r 4 l 86Jkg- 1K- 1, Latent heat of fusion
3.34x 105J/kg, Sice=2100Jkg-lK-I
,.).,..,)., What is thermal diffusivity? Where is thermal diffusivity used?
(4)
Question 4
[101
4.1 What are the dielectric properties of insulating material?
(2)
4.2 If an ionic crystal is subjected to an electric field of 1000 vm- 1 and the resulting
(4)
polarization 4.3 x 10-s cm2• Calculate the relative permittivity of NaCl. Solution:
Given Eo = 8.854 x 10-12 Fm- 1•
4.3 Explain the phenomenon of electric polarization in dielectric materials
(4)
Question 5
[10)
5.1 What is a ceramic? What type of atomic bonding characterizes the ceramics?
(2)
5.2 How structure of ceramics is determined? Predict the structure of FeO. Given ionic
radius ofFe 2+ = 0.77 nm and 0 2•is 0.14.
(4)
5.3 What is glass? Explain different types of glasses.
(4)
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Question 6
[10]
6.1 What is cross-linking in a polymer, and what is its significance?
(2)
6.2 Classify the following as addition and condensation polymers:
(4)
Terylene, Bakelite, Polyvinyl chloride, Polythene
6.3 Draw the structure of the monomer each of the following polymers-
(4)
(a) Poly (vinyl chloride), (b) Nylon-6.
Question 7
[10]
7.1 What are magnetic domains?
(2)
7.2 A paramagnetic material has FCC strncture with a cubic edge of 2.5 A0 • If the sah1ration
value of magnetization is 1.8 x 106 A m- 1, Calculate the magnetization contributed per
atom in Bohr magnetrons.
(4)
7.3
What are soft magnetic materials? Give its properties?
(4)
Question 8
[10]
8.1
Based on the type of matrix materials, classify composites
(2)
8.2 A continuous and aligned glass fiber-reinforced composite consists of 40 vol% of glass
fibers having a modulus of elasticity of 69 GPa and 60 vol% of a polyester resin that,
when hardened, displays a modulus of 3.4 GPa. Compute the modulus of elasticity
of this composite in the transverse direction
(4)
8.3 Mention and explain any four-parameter affecting the properties of fibrous composites? (4)
Question 9
[10]
9 .1 Explain why no hole is generated by the electron excitation involving a donor impurity
atom.
(2)
9.2 Find the resistivity of an intrinsic semiconductor with intrinsic concentration of2.5 x 1019
per m3. The mobilities of electrons and holes are 0.40 m2/ V-s and 0.20 m2/ V-s.
(4)
9.3 Classify the following semiconductor which are intrinsic, extrinsic, elemental and
compound semiconductor: Si, P-doped Ge, GaAs, Ge, CdS, Bi doped Si, S-doped Gap (4)
Question 10
[10]
10.1 What is semimetal
(2)
10.2 Determine the composition, in atom percent, of an alloy that consists of 97 wt% aluminium
and 3 wt.% copper
(4)
10.3 Define Slip? Mention the slip system for the FCC crystal structure
(4)
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