34
MCQ (Single Correct Answer)
Which of the following defects is also known as dislocation defect?
A
Frenkel defect
B
Schottky defect
C
Non-stoichiometric defect
D
Simple interstitial defect
35
MCQ (Single Correct Answer)
In the cubic close packing, the unit cell has ............. .
A
4 tetrahedral voids each of which is shared by four adjacent unit cells
B
4 tetrahedral voids within the unit cell
C
8 tetrahedral voids each of which is shared by four adjacent unit cells
D
8 tetrahedral voids within the unit cells
36
MCQ (Single Correct Answer)
The edge lengths of the unit cells in terms of the radius of spheres constituting fcc, bcc and simple cubic unit cells are respectively ............. .
A
$2 \sqrt{2 r}, \frac{4 r}{\sqrt{3}}, 2 r$
B
$\frac{4 r}{\sqrt{3}}, 2 \sqrt{2 r}, 2 r$
C
$2 r, 2 \sqrt{2 r}, \frac{4 r}{\sqrt{3}}$
D
$2 r, \frac{4 r}{\sqrt{3}}, 2 \sqrt{2 r}$
37
MCQ (Single Correct Answer)
Which of the following represents correct order of conductivity in solids?
A
$\kappa_{\text {metals }}>>\kappa_{\text {insulators }}<\kappa_{\text {semiconductors }}$
B
$\kappa_{\text {metals }}<<\kappa_{\text {insulators }}<\kappa_{\text {semiconductors }}$
C
$\kappa_{\text {metals }}$., $\kappa_{\text {semiconductors }}>\kappa_{\text {insulators }}=$ zero
D
$\kappa_{\text {metals }}<\kappa_{\text {semiconductors }}>\kappa_{\text {insulators }} \neq$ zero
38
MCQ (Multiple Correct Answer)
Which of the following is not true about the voids formed in 3 dimensional hexagonal close packed structure?
A
A tetrahedral void is formed when a sphere of the second layer is present above triangular void in the first layer
B
All the triangular voids are not covered by the spheres of the second layer
C
Tetrahedral voids are formed when the triangular voids in the second layer lie above the triangular voids in the first layer and the triangular shapes of these voids do not overlap
D
Octahedral voids are formed when the triangular voids in the second layer exactly overlap with similar voids in the first layer