McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Uncategorized topics .
| 351. |
Metal glasses differ from their crystalline counterparts in many ways. Chief application(s) of metal glasses include(s): |
| A. | bullet-proof glasses |
| B. | power transformers |
| C. | conducting wires |
| D. | all of the mentioned |
| Answer» B. power transformers | |
| Explanation: amorphous metals are not transparent and have relatively lower electrical conductivity. however, most metal glasses possess high magnetic susceptibility and low coercivity. | |
| 352. |
Soda-lime glass is the most common type of glass. The component present in largest w/w percentage is: |
| A. | sio2 |
| B. | al2o3 |
| C. | na2o |
| D. | cao |
| Answer» A. sio2 | |
| Explanation: glass inherits its transparency from crystalline sio2, also called quartz. | |
| 353. |
Lead-oxide glass is called “crystal glass” because: |
| A. | it contains crystalline pb |
| B. | it contains sio2 crystals |
| C. | it contains pbo crystals |
| D. | none of the mentioned |
| Answer» D. none of the mentioned | |
| Explanation: well, crystal glass is amorphous, not crystalline. this glass earns its name from its excellent decorative properties and high refractive index. | |
| 354. |
Crystallinity increases with increasing rate of cooling of a liquid. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: when a liquid is cooled rapidly, the particles get less time to move and arrange themselves in an orderly fashion and hence the crystallinity of the resulting solid decreases. | |
| 355. |
2 SINGLE CRYSTALS: UNIT CELL, CRYSTAL SYSTEMS, BRAVAIS LATTICES, DIRECTIONS AND PLANES IN A CRYSTAL, MILLER INDICES |
| A. | unit cell edge lengths |
| B. | distance between nearest neighbours |
| C. | cosine of angles between unit cell edges |
| D. | none of the mentioned view answer |
| Answer» A. unit cell edge lengths | |
| Explanation: point coordinate indices are the fractions which when multiplied by the corresponding unit cell edge lengths, provide the location of a given point in the crystallographic coordinate system. | |
| 356. |
In cubic crystals, crystallographic directions are arranged in families. Which of the following directions does not belong to the family <110>? |
| A. | [1 0 1] |
| B. | [11 0] |
| C. | [10 1̅] |
| D. | none of the mentioned view answer |
| Answer» D. none of the mentioned view answer | |
| Explanation: since the cubic lattice is symmetrical about all the three axes, the above directions are equivalent irrespective of order & sign and are part of same direction family. | |
| 357. |
Which of the following is a property of Miller indices? |
| A. | they uniquely identify a plane |
| B. | they are always positive |
| C. | they are not fractions |
| D. | none of the mentioned view answer |
| Answer» C. they are not fractions | |
| Explanation: two or more planes can have same miller indices which can be negative, zero or positive depending on the intercept on the axes. if the ratios of intercepts to lattice constants come out be fractional, then they are scaled to lowest integers to be represented as miller indices. | |
| 358. |
Miller indices for perpendicular planes are always the same. |
| A. | true |
| B. | false view answer |
| Answer» B. false view answer | |
| Explanation: it is true only for cubic lattices. for other systems, there is no simple relationship between planes with the same miller indices. | |
| 359. |
For destructive interference to take place, the path difference between the two waves should be: |
| A. | nλ |
| B. | 2nλ |
| C. | (n + 1/2)λ |
| D. | (2n + 1)λ |
| Answer» A. nλ | |
| Explanation: constructive interference occurs when the phase difference between two interfering waves is an integral multiple of 2π. also, the ratio of path difference to wavelength equals that of phase difference to 2π. | |
| 360. |
Bragg’s law is not a sufficient condition for diffraction by crystalline solids. |
| A. | true |
| B. | false view answer |
| Answer» A. true | |
| Explanation: atoms present at non-corner positions may result in out-of-phase scattering at bragg angles. | |
| 361. |
The Miller indices h, k, and l of parallel planes in a BCC lattice should satisfy which of the following X-ray diffraction reflection rules? |
| A. | h + k + l should be even |
| B. | h, k, and l should all be either even or odd |
| C. | h, k, and l should form pythagoras triplet |
| D. | all planes allow reflections view answer |
| Answer» A. h + k + l should be even | |
| Explanation: if the sum of miller indices becomes odd for a bcc lattice, destructive interference occurs. | |
| 362. |
Laue’s model pictures XRD as reflection from parallel crystalline planes. Reflection is different from refraction as: |
| A. | diffraction occurs throughout the bulk |
| B. | intensity of diffracted beams is less |
| C. | diffraction in crystals occurs only at bragg’s angles |
| D. | all of the mentioned view answer |
| Answer» D. all of the mentioned view answer | |
| Explanation: reflection is a surface | |
| 363. |
K-alpha x-rays have shorter wavelengths than K-beta x-rays? |
| A. | true |
| B. | false view answer |
| Answer» B. false view answer | |
| Explanation: k-alpha is formed from a transfer of electrons from l shell to k while k-beta result from m-to-k transition. hence k-alpha lines have lower energy (or longer wavelength). | |
| 364. |
Which of the following has a HCP crystal structure? |
| A. | w |
| B. | mo |
| C. | cr |
| D. | zr |
| Answer» D. zr | |
| Explanation: crystalline solids are classified | |
| 365. |
Amorphous solids have structure. |
| A. | regular |
| B. | linear |
| C. | irregular |
| D. | dendritic |
| Answer» C. irregular | |
| Explanation: materials in which the molecule is the basic structural solid and has an irregular structure is known as amorphous solid. crystalline solids, on the other hand, usually are arranged in a regular manner. | |
| 366. |
At iron changes its BCC structure to FCC. |
| A. | 308oc |
| B. | 568oc |
| C. | 771oc |
| D. | 906oc |
| Answer» D. 906oc | |
| Explanation: similar to metallic crystals, a few non-metallic crystals also change form due to temperature and pressure differences. this process is termed as polymorphism. iron changes from bcc at room temperature to fcc form at 906oc. | |
| 367. |
At room temperature, tin is formed into |
| A. | gray tin |
| B. | white tin |
| C. | red tin |
| D. | yellow tin |
| Answer» B. white tin | |
| Explanation: similar to metallic crystals, a few non-metallic crystals also change form due to temperature and pressure differences. tin crystallizes in a non-metallic diamond structure (gray tin) at low temperatures. at | |
| 368. |
Which of the following is a property of non-metallic crystals? |
| A. | highly ductile |
| B. | less brittle |
| C. | low electrical conductivity |
| D. | fcc structure |
| Answer» C. low electrical conductivity | |
| Explanation: non-metallic crystals are less ductile and have low electrical conductivity. on the other hand, metallic crystals are differing since they are more ductile and have high electrical conductivity. | |
| 369. |
Which of the following is not an amorphous material? |
| A. | glass |
| B. | plastics |
| C. | lead |
| D. | rubbers |
| Answer» C. lead | |
| Explanation: materials in which the molecule is the basic structural solid and has an irregular structure are known as amorphous solid. most amorphous materials are polymers such as plastics and rubbers. | |
| 370. |
The smallest portion of the lattice is known as |
| A. | lattice structure |
| B. | lattice point |
| C. | bravais crystal |
| D. | unit cell |
| Answer» D. unit cell | |
| Explanation: lattice is defined as the regular geometrical arrangement of points in crystal space. the unit cell is the smallest portion of the lattice, which when repeated in all directions gives rise to a lattice structure. | |
| 371. |
A unit cell that contains lattice points only at the corners is known as |
| A. | primitive unit cell |
| B. | secondary unit cell |
| C. | layered unit cell |
| D. | derived unit cell |
| Answer» A. primitive unit cell | |
| Explanation: if a unit cell chosen contains lattice points only at its corners, it is called a primitive or simple unit cell. it contains only one lattice point since each point at the eight corners is shared equally with adjacent unit cells. | |
| 372. |
The axial relationship of a monoclinic crystal system is given as |
| A. | a = b = c |
| B. | a = b ≠ c |
| C. | a ≠ b = c |
| D. | a ≠ b ≠ c |
| Answer» D. a ≠ b ≠ c | |
| Explanation: the crystal system is a format by which crystal structures are classified. | |
| 373. |
The axial relationship of a rhombohedral crystal system is given as |
| A. | a = b = c |
| B. | a = b ≠ c |
| C. | a ≠ b = c |
| D. | a ≠ b ≠ c |
| Answer» A. a = b = c | |
| Explanation: the crystal system is a format by which crystal structures are classified. | |
| 374. |
The interracial angles of a hexagonal crystal system are given by |
| A. | α = β = ϒ = 90o |
| B. | α = β = 90o ϒ = 120o |
| C. | α = β = ϒ ≠ 90o |
| D. | α ≠ β ≠ ϒ ≠ 90o |
| Answer» B. α = β = 90o ϒ = 120o | |
| Explanation: the crystal system is a system by which crystal structures are classified. | |
| 375. |
The interracial angles of a triclinic crystal system are given by |
| A. | α = β = ϒ = 90o |
| B. | α = β = 90o ϒ = 120o |
| C. | α = β = ϒ ≠ 90o |
| D. | α ≠ β ≠ ϒ ≠ 90o |
| Answer» D. α ≠ β ≠ ϒ ≠ 90o | |
| Explanation: the crystal system is a system by which crystal structures are classified. | |
| 376. |
What is the atomic radius of a BCC crystal structure? |
| A. | a/2 |
| B. | a/4 |
| C. | a√2/4 |
| D. | a√3/4 |
| Answer» D. a√3/4 | |
| Explanation: atomic radius is defined as half the distance between the centers of two neighboring atoms. the atomic radius of a simple cube and hcp is a/2 respectively, whereas it is a√2/4 and a√3/4 for fcc and bcc respectively. | |
| 377. |
What is the coordination number of a simple cubic structure? |
| A. | 6 |
| B. | 8 |
| C. | 10 |
| D. | 12 |
| Answer» A. 6 | |
| Explanation: coordination number is defined as the number of nearest neighboring atoms in crystals. the coordination number for the simple cubic structure is 6, whereas it is 8 and 12 for bcc and fcc respectively. | |
| 378. |
What is the atomic packing factor of BCC structure? |
| A. | 0.54 |
| B. | 0.68 |
| C. | 0.74 |
| D. | 0.96 |
| Answer» B. 0.68 | |
| Explanation: the density of packing in a crystal is determined using the atomic packing factor (apf). the apf of fcc and hcp structures is 0.74, and 0.54 for simple cubic structure, whereas it is 0.68 for bcc structure. | |
| 379. |
Which of the following is a point defect in crystals? |
| A. | edge dislocation |
| B. | interstitialcies |
| C. | grain boundaries |
| D. | cracks |
| Answer» B. interstitialcies | |
| Explanation: crystal defects are classified as point defects, line defects, and boundary defects. point defects include vacancies, impurities, interstitialcies, and electronic defects. | |
| 380. |
The defect that occurs due to a displacement of an ion is known as |
| A. | vacancy defect |
| B. | schottky defect |
| C. | frankel defect |
| D. | interstitial defect |
| Answer» C. frankel defect | |
| Explanation: frankel defect occurs due to a displacement of an ion from the crystal lattice. it is related to the interstitial defect, where an ion simply occupies a position between regular atoms. | |
| 381. |
Which defect does the following figure depict? |
| A. | vacancy defect |
| B. | schottky defect |
| C. | frankel defect |
| D. | interstitial defect |
| Answer» B. schottky defect | |
| Explanation: when a pair of positive and negative ions both disappear from a crystal lattice, the effect is called a schottky defect. it is closely related to vacancy defects where simply an ion is missing. | |
| 382. |
Which defect does the following diagram represent? |
| A. | vacancy defect |
| B. | schottky defect |
| C. | frankel defect |
| D. | interstitial defect |
| Answer» D. interstitial defect | |
| Explanation: interstitial defects occur when an atom occupies an empty position in a crystal lattice. self-interstitial effects occur due to their own atoms, while others occur due to a foreign substance. | |
| 383. |
occurs when a foreign substance replaces an atom in a crystal. |
| A. | vacancy defect |
| B. | substitutional impurity |
| C. | frankel defect |
| D. | interstitial impurity |
| Answer» B. substitutional impurity | |
| Explanation: a substitutional impurity occurs due to the occupation of a foreign atom in place of an atom in a crystal. on the other hand, interstitial impurities occur when a regular atom occupies a random space in the crystal lattice. | |
| 384. |
A disturbance in a region between two ideal parts of a crystal is known as |
| A. | boundary defect |
| B. | point defect |
| C. | line defect |
| D. | volume defect |
| Answer» C. line defect | |
| Explanation: line defect is regarded as a disturbed region between two perfect parts of a crystal. they may be of either edge dislocation type or screw dislocation. | |
| 385. |
In screw dislocation, the Burger’s vector lies to the dislocation line. |
| A. | perpendicular |
| B. | parallel |
| C. | at an angle |
| D. | sideways |
| Answer» B. parallel | |
| Explanation: the burger’s vector in screw dislocation lies parallel to the dislocation line along the axis of a line of atoms in the same plane. on the other hand, it lies at an angle for edge dislocation. | |
| 386. |
Generation of dislocations can be identified using |
| A. | schottky mechanism |
| B. | burger’s vector |
| C. | twist |
| D. | frank-read mechanism |
| Answer» D. frank-read mechanism | |
| Explanation: the frank-read mechanism | |
| 387. |
What are one-dimensional defects? |
| A. | boundary defect |
| B. | point defect |
| C. | line defect |
| D. | volume defect |
| Answer» C. line defect | |
| Explanation: when compared geometrically, line defects are seen as one-dimensional defects. line defects are also known as dislocations, with common types as edge and screw dislocations. | |
| 388. |
What are two-dimensional defects? |
| A. | boundary defect |
| B. | point defect |
| C. | line defect |
| D. | volume defect |
| Answer» A. boundary defect | |
| Explanation: the defects that occur on the surface of a material are known as surface or boundary defects. geometrically, they are regarded as two-dimensional defects. | |
| 389. |
How is the dislocation energy defined? |
| A. | j m-1 |
| B. | j m-2 |
| C. | m-2 |
| D. | n m-1 |
| Answer» A. j m-1 | |
| Explanation: dislocation energy is defined ad joule per meter and is denoted by e. dislocation density is defined as meter per cubic meter or simply as per meter square. | |
| 390. |
Which one of the following, is a line imperfection? |
| A. | grain boundary |
| B. | tilt boundary |
| C. | dislocation |
| D. | stacking fault |
| Answer» C. dislocation | |
| Explanation: dislocations look like lines in the lattice, which are one dimensional. so it falls under the category of line imperfections. while grain boundary, tilt boundary and stacking fault are surface imperfections. | |
| 391. |
What is the range of dislocation density in pure and unhardened metals? |
| A. | 1010 – 1012 m-2 |
| B. | 1014 – 1016 m-2 |
| C. | 104 – 106 m-2 |
| D. | 108 – 1010 m-2 |
| Answer» A. 1010 – 1012 m-2 | |
| Explanation: pure unhardened metals (real crystal) contain large number of dislocations of the order of1010 – 1012 m-2. so these can easily be deformed. | |
| 392. |
What is unit of dislocation density? |
| A. | m |
| B. | m-2 |
| C. | kg/m3 |
| D. | m-3 |
| Answer» B. m-2 | |
| Explanation: dislocation density is defined as number of lines in a unit volume. so the unit of dislocation density is m/m3 or m-2. | |
| 393. |
6 BURGER VECTORS, STACKING FAULTS - ROLE OF |
| A. | increase in strength |
| B. | decrease in strength |
| C. | increase or decrease in strength depending on dislocation density |
| D. | don’t affect strength of metal |
| Answer» C. increase or decrease in strength depending on dislocation density | |
| Explanation: if dislocation density is in range 1010 – 1012 m-2, it decreases the strength by easy plastic deformation. on the other hand, if it exceeds to 1016 m-2, these causes strengthening of metal by interaction to imperfections. | |
| 394. |
The number of dislocations increases drastically during |
| A. | solidification |
| B. | plastic deformation |
| C. | elastic deformation |
| D. | heat treatment |
| Answer» B. plastic deformation | |
| Explanation: dislocations increase in number drastically during plastic deformation. it is due to the formation of a frank-read source. | |
| 395. |
Positive edge dislocation is denoted by |
| A. | ↶ |
| B. | ↷ |
| C. | ꓕ |
| D. | ꓔ |
| Answer» C. ꓕ | |
| Explanation: positive edge dislocation is represented as ‘ꓕ’ (inverted ꓔ) because the extra half plane lies above the shear plane. ‘ꓔ’ is used for negative edge dislocation. ‘↶’ and ‘↷’ are used to represent screw dislocations. | |
| 396. |
Edge dislocation introduces shear strain only. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: edge dislocations cause compressive, tensile and shear lattice strains. | |
| 397. |
What term is used for the defect, produced by an array of dislocations that produces a small difference in orientation between the adjoining lattices? |
| A. | tilt boundary |
| B. | twist boundary |
| C. | free surface |
| D. | low angle grain boundary |
| Answer» D. low angle grain boundary | |
| Explanation: the array of dislocations produces an angular mismatch between the lattices, which is referred to as low angle grain boundary. these have an angle less than 100. | |
| 398. |
Which statement is false? |
| A. | plastic deformation decreases dislocation density. |
| B. | strain hardening is the increase of dislocation density with plastic deformation. |
| C. | slip plane is the crystallographic plane of dislocation motion. |
| D. | dislocation can change its plane of motion by climb on high temperatures. |
| Answer» A. plastic deformation decreases dislocation density. | |
| Explanation: plastic deformation increases the dislocation density. plastic deformation causes generation of dislocations due to the frank-read source. all other statements are correct. | |
| 399. |
Most crystalline materials have dislocations in their as formed state. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: crystalline materials have dislocations due to stresses (mechanical, thermal …) associated with the forming processes. thus forming processes are the source of dislocations. | |
| 400. |
Dislocation density can vary from |
| A. | 105 – 1012 cm-2 |
| B. | 105 – 1012 m-2 |
| C. | 108 – 1010 cm-2 |
| D. | 106 – 1010 cm-2 |
| Answer» A. 105 – 1012 cm-2 | |
| Explanation: dislocation density varies in metals from 105 cm-2 (in carefully solidified metal) to 1012 cm-2 (in heavily deformed metal). it depends on various parameters as degree of deformation, temperature etc. | |
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