Engineering Questions with Answers - Multiple Choice Questions
Materials Science MCQ’s – Classification of Crystallographic Defects
1 - Question
Frenkel defect belongs to which of the following classes?
a) Point defect
b) Linear dislocation
c) Interfacial defect
d) Bulk defect
View Answer
Explanation: Frenkel defect occurs when some of the smaller ions shift from their lattice point to interstitial positions.
2 - Question
The ratio of the number of vacancies to a total number of lattice points for a metal near melting temperature is of the order of 10-4. For lower temperatures, the ratio:
a) increases
b) decreases
c) remains the same
d) may increase or decrease depending on the metal
View Answer
Explanation: At lower temperature, less energy is available in the system which means less number of atoms are able to leave their lattice sites to create vacancies.
3 - Question
Foreign species is present in which of the following defects?
a) Interstitial
b) Vacancy
c) Substitution
d) All of the mentioned
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Explanation: In substitution defect, particles of other species having similar sizes replace the host particles in a lattice whereas interstitial defect occurs when particles of the same species are present at interstitial voids.
4 - Question
Edge dislocation and screw dislocation are linear crystalline defects.
a) True
b) False
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Explanation: Edge dislocation and screw dislocations are linear crystalline defects or line defects.
5 - Question
Burger vectors are relevant to which of the following crystalline defects?
a) Point defects
b) Line defects
c) Interfacial defects
d) Bulk defects
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Explanation: Burger vector denotes the magnitude and direction of a line defect.
6 - Question
Pores & cracks in crystalline solids can be classified as bulk defects.
a) True
b) False
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Explanation: Pores and cracks are not localized to a particular point or edge, but have sizes much larger than atomic dimensions.
7 - Question
Ferromagnetic material shows strong para-magnetic behaviour due to the formation of domains. These domains belong to:
a) Point defects
b) Linear defects
c) Interfacial defects
d) Bulk defects
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Explanation: In ferromagnetic materials, the alignment of magnetic dipoles vary across domain walls. These walls spread across large surfaces but have negligible thickness.
8 - Question
Electrical conductivity of the specimen is a requirement for which of the following microscopic examination techniques?
a) Optical microscopy
b) Transmission electron microscopy
c) Scanning electron microscopy
d) Scanning probe microscopy
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Explanation: Non-conducting specimen will develop electrostatic charge due to an incident electron beam. This field tends to produce faults in the signal interpretation.
9 - Question
Which of the following point defects is non-stoichiometric in nature?
a) Schottky defect
b) Metal excess defect
c) Interstitial defect
d) Impurity defect
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Explanation: When alkali halides are heated in an atmosphere of the constituent metal, halide ions diffuse to the surface to react with the vapour particles. This results in excess of cations over anions.
10 - Question
The solubility of solute in a solvent in a solid solution is governed by Hume-Rothery rules. The solubility is more if:
a) radii of solute are much smaller than that of solvent
b) solute an solvent have a similar crystal structure
c) solute has low valence
d) all of the mentioned
View Answer
Explanation: For high solubility, the solute-solvent pair should have similar radii, crystal structure, and electronegativity. Moreover, for other factors being equal, a solute with higher valence is more soluble than one having lower valence.