| Assertion (A): | In a particular point defect, an ionic solid is electrically neutral, even if few of its cations are missing from its unit cells. |
| Reason (R): | In an ionic solid, Frenkel defect arises due to dislocation of cation from its lattice site to interstitial site, maintaining overall electrical neutrality. |
| 1. | (A) is false but (R) is true. |
| 2. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| 3. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
| 4. | (A) is true but (R) is false. |
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 opposite to the direction of magnetic field. |
| 2. | domains are not affected by magnetic field. |
| 3. | domains get randomly oriented. |
| 4. | all the domains get oriented in the direction of magnetic field. |
Which statements among the following is not correct?
| 1. | When conduction band and valence band overlap, a semiconductor is obtained |
| 2. | Ferrimagnetism arises due to the alignment of magnetic moments of the domains in the substance in parallel and anti-parallel directions in unequal numbers |
| 3. | Replacing some silicon atoms by boron atoms in crystal of silicon produces p-type semiconductor |
| 4. | Replacing some germanium atoms by phosphorus atoms in a crystal of germanium produces n-type semiconductor |
| List-I (Defects) |
List-II (shown by) |
| (a) Frenkel defect | (i) non-ionic solids and density of the solid decreases. |
| (b) Schottky defect | (ii) non-ionic solids and density of the solid increases. |
| (c) Vacancy defect | (iii) ionic solids and density of the solid decreases. |
| (d) Interstitial defect |
(iv) ionic solids and the density of the solid remains constant. |
| (a) | (b) | (c) | (d) | |
| 1. | (i) | (ii) | (iii) | (iv) |
| 2. | (i) | (iii) | (ii) | (iv) |
| 3. | (iv) | (iii) | (ii) | (i) |
| 4. | (iv) | (iii) | (i) | (ii) |
A group 14 element is converted into n-type semiconductor by doping it with :
1. Boron
2. Aluminium
3. Phosphorous
4. All of the above.