RRB JE Stage II : Mechanical Engineering Quiz | 20th August

Dear aspirants,

RRB JE Stage II exam is scheduled to be conducted from 28th August to 1st September 2019. The overall merit for the selection will be made on the basis of the marks scored in stage II, so candidates need to prepare thoroughly for the second stage. To help the aspirants, Adda247 has come up with a study plan in which we will provide you daily quizzes of all technical subjects. The below quiz will be helpful for the candidates who opted Mechanical as the exam group in RRB JE stage II.

Q1. Which one of the following pairs is not correctly matched?
(a) Point defect in crystal lattice Self interstitial
(b) Linear defect in crystal lattice: Grain boundary
(c) Planar defect in crystal lattice: External surface
(d) Volume defect in crystal lattice : Other phases

S1. Ans.(b)
Sol. Grain boundary is planar defect.
Point defect: Vacancy, interstitial impurity,substitutional impurity, self substitution, self interstitial.Frenkel
Line defect: Edge and screw dislocation
Planar defect: Grain boundary, twin boundary stacking fault. Low angle
boundary

Q2. A screw dislocation
1. Lies parallel to its Burger’s vector
2. Lies perpendicular to its Burger’s vector
3.Moves in a perpendicular direction to the Burger’s vector
4.Moves in an inclined direction to the Burger’s vector
Select the correct answer using the codes given below:
(a) 1 and 4
(b) 1 and 3
(c) 2 and 3
(d) 2 and 4

S2. Ans.(b)
Sol. Screw dislocation lies parallel to Burger vector and moves in perpendicular direction to Burger vector. Edge dislocation-Burger vector is normal to dislocation line and movement will be parallel to burger vector.

Q3. Assertion (A): Unlike in the case of ionic bonds, the coordination numbers for covalently bonded atoms are not controlled by the radii ratio.
Reason (R): A covalent bond has a specific direction of bonding in space.
(a) both A and R are true and R is the correct explanation of A
(b) both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

S3. Ans.(d)
Sol. The correct option is (d) 1.e, Assertion is false but R is true
:The covalent is directional i.e., it is between specific atoms and may exist only in the direction between one atom and another that participate in the electron sharing. :lonic bond is termed non-directional that is the magnitude of the bond is equal in all direction around an ion.
Coordination number (Z)It is the number of nearest neighbours in a crystal structure. It depends on the radius ratio +type of hybridigation in covalent ones and the radius ratio in ionic structure. The CN is strongly controlled by radius ratio, the radius of an ion (or atom) may (and usually does) change as a function of CN.

Q4. Consider the following statements about FCC and HCP crystal structure:
1.Both have same coordination number and atomic packing fraction.
2. Both represent closely packed crystal structures.
3.Both structures are generated by stacking of close packed planes on top of one another, but only the stacking sequence is different.
Which of these statements are correct?
(a) 1 and 2
(b) 2 and 3
(c) 1, 2 and 3
(d) 1 and 3

S4. Ans.(c)
Sol. The correct option is (c) i.e., all the three statements are correct. :As the metallic bond is non-directional, many metals tend to form highly symmetrical close-packed structures, which result in their relatively high densities. The most commonclose and importantare face centrad cubic (FCC) and hexagonal close packet (HCP) structures. Both structure are generated by stacking of packed planes on top of one another, but only stacking sequence is different.

Q5. In Zinc Blende structure each atom is surrounded by four atoms of the opposite kind which are located at the corners of which one of the following?
(a) Tetrahedron
(b) Hexahedron
(c) Cube
(d) Orthorhombic

S5. Ans.(a)
Sol. In Zinc blende structure each atom is surrounded by four atoms of the opposite kind which are located at the corner of a tetrahedron.

Q6. Which one of the following is the correct ascending order of packing density for the given crystal structures of metals?
(a) Simple cubic – Face central cubic – Body centrad cubic
(b) Body centred cubic -Simple cubic – Face centred cubic
(c) Simple cubic – Body centred cubic – Face centred cubic
(d) Body centred cubic – Face centred cubic- Simple cubic

S6. Ans.(c)
Sol. Density:ρ
where n=number of atoms associated with each unit cell
A = Atomic weight
Vc= Volume of the unit cell
Na = Avogadro’s number (6.023 x 1023 atoms/mol)
n= 1-simple cubic
= 2- BCC
=4- FCC

Q7. Which one of the following statements is correct in the case of screw dislocations?
(b= Burger’s Vector; t=Imaginary Vector)
(a)b is perpendicular to t
(b) b is parellel to t
(c) b is inclined to t
(d) b and t are non-coplaner and nor intersecting

S7. Ans.(b)
Sol. Burger vector (b) is parallel to imaginary sector (t) in case of screw dislocation.

Q8. Which one of the following crystal systems is valid for gold?
(a) Orthogonal
(b) Cubic
(c) Hexagonal
(d) Triclinic

S8. Ans.(b)
Sol. Gold, Silver, Nickel, Copper and Aluminium-Al are having F.C.C (Face Centred Cubic) crystal structure.

Q9. Which one of the following is correct for ‘Climb’?
(a) Dislocation moves parallel to the slip plane
(b) Dislocation moves perpendicular to the slip plane
(c) Sliding of one plane of atoms over the other plane
(d) Dislocation moves from a slip plane to another slip plane

S9. Ans.(b)
Sol. Climb is a dislocation movement in which dislocation moves from one slip plane to another slip plane. Where as Glide is a dislocation movement in which dislocation moves within the same slip plane.

Q10. Which one of the following defects is Schottky defect?
(a) Vacancy defect
(b) Compositional defect
(c) Interstitial defect
(d) Surface defect

S10. Ans.(a)
Sol. Schottky defect is a type of vacancy defect in which cation vacancy is associated with anion vacancy.

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