The correct order of the packing efficiency in different types of unit cells is-
1. Fcc < Bcc < Simple cubic
2. Fcc > Bcc > Simple cubic
3. Fcc < Bcc > Simple cubic
4. Bcc < Fcc > Simple cubic
Correct statement among the following regarding conductivity in solids is -
1.
2.
3.
4.
Match the defects given in Column I with the statements given in Column II.
Column I | Column II |
A. Simple vacancy defect | 1. Shown by non-ionic solids and increases the density of the solid |
B. Simple interstitial defect | 2. Shown by ionic solids and decreases the density of the solid |
C. Frenkel defect | 3. Shown by non-ionic solids and decreases the density of the solid |
D. Schottky defect | 4. Shown by ionic solids and density of the solid remains the same |
Codes
A | B | C | D | |
1. | 3 | 1 | 4 | 2 |
2. | 1 | 2 | 3 | 4 |
3. | 1 | 4 | 3 | 2 |
4. | 4 | 1 | 3 | 2 |
Match the types of defects given in Column I with the statement given in Column II.
Column I | Column II |
A. Impurity defect | 1. NaCl with anionic sites called F-centres |
B. Metal excess defect | 2. FeO with Fe3+ |
C. Metal deficiency defect | 3. NaCl with Sr2+ and some cationic sites vacant |
Codes
A | B | C | |
1. | 2 | 3 | 1 |
2. | 3 | 1 | 2 |
3 | 1 | 2 | 3 |
4. | 2 | 1 | 3 |
Match the items given in Column I with the items given in Column II.
Column I | Column II |
A. Mg in solid state | 1. p-type semiconductor |
B. MgCl2 in molten state | 2. n-type semiconductor |
C. Silicon with phosphorus | 3. Electrolytic conductors |
D. Germanium with boron | 4. Electronic conductors |
Codes
A | B | C | D | |
1. | 2 | 3 | 4 | 1 |
2. | 1 | 2 | 3 | 4 |
3. | 1 | 4 | 3 | 2 |
4. | 4 | 3 | 2 | 1 |
Match the type of packing given in Column I with the items given in Column II.
Column I | Column II |
A. Square close packing in two dimensions | 1. Triangular voids |
B. Hexagonal close packing in two dimensions | 2. Pattern of spheres is repeated in every fourth layer |
C. Hexagonal close packing in three dimensions | 3. Coordination number = 4 |
D. Cubic close packing in three dimensions | 4. Pattern of sphere is repeated in alternate layers |
Codes
A | B | C | D | |
1. | 3 | 2 | 4 | 1 |
2. | 1 | 2 | 3 | 4 |
3. | 3 | 1 | 4 | 2 |
4. | 4 | 1 | 3 | 2 |
Select the correct option based on statements below:
Assertion (A): | Semiconductors are solids with conductivities in the range from 10-6 — 104 ohm-1 m-1. |
Reason (R): | Intermediate conductivity in semiconductors is due to a partially filled valence band. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
3. | (A) is true but (R) is false. |
4. | (A) is false but (R) is true. |
A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because:
1. | All the domains get oriented in the direction of the magnetic field. |
2. | All the domains get oriented in the direction opposite to the direction of the magnetic field. |
3. | Domains get oriented randomly. |
4. | Domains are not affected by the magnetic field. |
The incorrect statement among the following is:
1. | Paramagnetic substances are weakly attracted by magnetic field. |
2. | Ferromagnetic substances cannot be magnetised permanently. |
3. | The domains in antiferromagnetic substances are oppositely oriented with respect to each other. |
4. | Pairing of electrons cancels their magnetic moment in the diamagnetic substances. |
Doping causes-
1. Dislocation defect.
2. Schottky defect.
3. Frenkel defect.
4. Electronic defect.