1. An octahedral void is surrounded by:
a) 8 atoms
b) 18 atoms
c) 6 atoms
d) 16 atoms
Explanation: An octahedral void resembles a regular octahedron with atoms situated at all the six vertices.
2. Which of the following is a property of amorphous solids?
a) Sharp melting point
b) Isotropy
c) Long range order
d) Definite heat of fusion
Explanation: Due to irregularity in structure, the average of physical properties like density, thermal and electrical conductivity etc. is same along any direction for a particular amorphous solid.
3. Which of the following is a crystalline solid?
a) Copper wire
b) Glass bottle
c) Polythene bag
d) Rubber ball
Explanation: Copper wires are made of crystalline copper. In fact, most metallic objects are crystalline. However, research for the large-scale production of amorphous metals is in progress.
4. The smallest portion of a crystal which when repeated in different directions generates the entire crystal is called:
a) Lattice points
b) Crystal lattice
c) Unit cell
d) None of the mentioned
Explanation: Unit cell is the smallest unit of a crystal which repeats itself to generate the crystal. Lattice point represents the centres of atoms in a unit cell. Crystal lattice refers to the entire structure of a crystalline solid.
5. Which of the following is not a property of metal glass?
a) Transparent
b) Poor thermal conductivity
c) High magnetic susceptibility
d) None of the mentioned
Explanation: Metal glass is a form of metal which like glass, is amorphous but not transparent. Most of the metal glasses are alloys, having high yield strength and high elastic strain limits. High magnetic susceptibility, low coercivity and comparatively higher electrical resistance than their crystalline counterparts make them an ideal material for power transformers.
6. Grain boundaries are one of the causes of corrosion of metals?
a) True
b) False
Explanation: Grain boundaries are the regions that separate two grains in polycrystalline metallic solids. The absence of properly defined structure results in residual stresses. Hence, grain boundaries are the weak spots in the structure and are often the site of a fracture.
7. Most Bravais lattices are of the type:
a) Primitive unit cell
b) Body centered unit cell
c) End centered unit cell
d) Face centered unit cell
Explanation: Out of 14 naturally occurring Bravais lattices, 7 are primitive. Remaining seven consists of 3 body centered, 2 face centered and 2 end centered unit cells.
8. In which of the following Bravais lattices, not all axial angles are right angles?
a) Tetragonal
b) Rhombohedral
c) Orthorhombic
d) Cubic
Explanation: A rhombohedral is a prism whose base is shaped as a non-square rhombus. Hence two of its six faces are rhombuses while others are rectangles. This results in a geometry for which two of the axial angles are right angles but the third is not.
9. Which of the following Bravais lattices exist as face centered unit cell?
a) Orthorhombic
b) Monoclinic
c) Tetragonal
d) None of the mentioned
Explanation: Orthorhombic lattice exists as all four types of unit cells. Besides primitive cell, monoclinic lattice exists only as end centered cell while tetragonal exists only as body centered lattices.
10. Coordination number for an ideal BCC metallic crystal is:
a) 8
b) 6
c) 12
d) Varies for different metals
Explanation: Consider the atom at the body center. It is touched by all the atoms present at the vertices of the cubic unit cell. We know that a cube has 8 vertices.