Q. No.
The most efficient packing is present in -
1. HCP and BCC
2. HCP and CCP
3. BCC and CCP
4. BCC and Simple cubic cell
The incorrect statement among the following regarding hexagonal close packing is:
| 1. | The coordination number is 12. |
| 2. | It has 74% packing efficiency. |
| 3. | Tetrahedral voids of the second layer are covered by the spheres of the third layer. |
| 4. | In this arrangement, spheres of the fourth layer are exactly aligned with those of the first layer. |
Same coordination number for cations and anions is present in:
| 1. | Cl- ions form Fcc lattice and Na+ ions occupy all octahedral voids of the unit cell. |
| 2. | Ca2+ ions form Fcc lattice and F- ions occupy all the eight tetrahedral voids of the unit cell. |
| 3. | O2- ions form Fcc lattice and Na+ ions occupy all the eight tetrahedral voids of the unit cell. |
| 4. | S2- ions form Fcc lattice and K+ ions go into alternate tetrahedral voids of the unit cell. |
The coordination number of a square close-packed structure in two dimensions is -
1. 2
2. 3
3. 4
4. 6
Doping causes-
1. Dislocation defect.
2. Schottky defect.
3. Frenkel defect.
4. Electronic defect.
Silicon doped with electron rich impurity forms -
1. p-type semiconductor.
2. n-type semiconductor.
3. Intrinsic semiconductor.
4. Insulator.
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. |
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 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
Dislocation defect is also known as-
1. Frenkel defect.
2. Schottky defect.
3. Non-stoichiometric defect.
4. Simple interstitial defect.
© 2024 GoodEd Technologies Pvt. Ltd.