In the cubic close packing, the unit cell has ......... .
1. | 4 tetrahedral voids each of which is shared by four adjacent unit cells. |
2. | 4 tetrahedral voids within the unit cell. |
3. | 8 tetrahedral voids each of which is shared by four adjacent unit cells. |
4. | 8 tetrahedral voids within the unit cells. |
The edge lengths of the unit cells in terms of the radius of spheres constituting fcc, bcc, and simple cubic unit cells are respectively -
1.
2.
3.
4.
Correct statement among the following regarding conductivity in solids is -
1.
2.
3.
4.
Which of the following is not true about the voids formed in a 3-dimensional hexagonal close-packed structure?
I. | A tetrahedral void is formed when a sphere of the second layer is present above the triangular void in the first layer |
II. | All the triangular voids are not covered by the spheres of the second layer |
III. | 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 |
IV. |
Octahedral voids are formed when the triangular voids in the second layer exactly overlap with similar voids in the first layer |
The correct choice among the given is -
1. (I, II)
2. (II, III)
3. (III, IV)
4. (I, III)
The value of the magnetic moment is zero in the case of antiferromagnetic substances because the domains -
I. | Get oriented in the direction of the applied magnetic field |
II. | Get oriented opposite to the direction of the applied magnetic field |
III. | Are oppositely oriented with respect to each other without the application of magnetic field |
IV. | Cancel out each other’s magnetic moment |
The correct choice among the given is -
1. (I, II)
2. (II, III)
3. (III, IV)
4. (I, IV)
Incorrect(s) statement among the following:
I. | Vacancy defect results in a decrease in the density of the substance. |
II. | Interstitial defects results in an increase in the density of the substance. |
III. | Impurity defect has no effect on the density of the substance. |
IV. | Frenkel defect results in an increase in the density of the substance. |
1. (I, II)
2. (II, III)
3, (III, IV)
4. (I, IV)
The correct statements among the following about metals are-
I. | Valence band overlaps with the conduction band. |
II. | The gap between the valence band and conduction band is negligible |
III. | The gap between the valence band and conduction band cannot be determined |
IV. | Valence band may remain partially filled |
1. (I, II, III)
2. (II, III, IV)
3. (I, III, IV)
4. (I, II, IV)
Under the influence of the electric field, which of the following statement is true about the movement of electrons and holes in a p-type semiconductor?
I. | Electron will move towards the positively charged plate through electron holes |
II. | Holes will appear to be moving towards the negatively charged plate |
III. | Both electrons and holes appear to move towards the positively charged plate |
IV. | Movement of electrons is not related to the movement of holes |
The correct choice among the given is-
1. (I, II)
2. (II, III)
3. (III, IV)
4. (I, IV)
Consider the following statements about semiconductors.
I. | Silicon doped with electron-rich impurity is a p-type semiconductor. |
II. | Silicon doped with an electron-rich impurity is an n-type semiconductor. |
III. | Delocalised electrons increase the conductivity of doped silicon. |
IV. | An electron vacancy increases the conductivity of n-type semiconductor. |
1. I and II
2. II and III
3. III and IV
4. I and IV
An excess of potassium ions makes KCl crystals appear violet or lilac in colour because-
a. | Some of the anionic sites are occupied by an unpaired electron |
b. | Some of the anionic sites are occupied by a pair of electrons |
c. | There are vacancies at some anionic sites |
d. | F-centres are created which impart colour to the crystals |
The correct choice among the given is-
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)