21. At what temperatures domains lose their ferromagnetic properties?
22. Resistivity of Ge is
23. Superconductivity is destroyed
24. Which one of the following is the best definition of a superconductor?
25. Match List-I with List-II and select the correct answer:
List-I
List-II
a. Ferro-magnetism
1. d.c. electrical resistivity vanishes at the critical temperature TC
b. Semiconductor
2. Doping with impurity increases the electrical conductivity
c. Optical property of solid
3. An internal molecular field BM which is proportional to magnetization M exists at each dipole and aligns it parallel to other dipoles
d. Superconductivity
4. Above the Neel temperature the dipoles become randomly oriented
5. The conductivity of crystalline semiconductors and dielectrics increases by radiation incident
| List-I | List-II |
| a. Ferro-magnetism | 1. d.c. electrical resistivity vanishes at the critical temperature TC |
| b. Semiconductor | 2. Doping with impurity increases the electrical conductivity |
| c. Optical property of solid | 3. An internal molecular field BM which is proportional to magnetization M exists at each dipole and aligns it parallel to other dipoles |
| d. Superconductivity | 4. Above the Neel temperature the dipoles become randomly oriented |
| 5. The conductivity of crystalline semiconductors and dielectrics increases by radiation incident |
26. Which of the following statements in NOT true?
27. Which one of the following materials is a ceramic material?
28. Consider the following statements:
The conductivity of a metal has negative temperature coefficient since:
1. The electron concentration increase with temperature.
2. The electron mobility decreases with temperature.
3. The electron-lattice scattering rate increases with temperature.
Which of the above statements is/are correct?
The conductivity of a metal has negative temperature coefficient since:
1. The electron concentration increase with temperature.
2. The electron mobility decreases with temperature.
3. The electron-lattice scattering rate increases with temperature.
Which of the above statements is/are correct?
29. Piezoelectricity is the reverse effect of
30. Consider the following statements:
He-Ne laser
1. gives continuous output
2. emits red light
3. requires a DC magnet
4. can be voice modulated by using a Kerr cell
Which of these statements are correct?
He-Ne laser
1. gives continuous output
2. emits red light
3. requires a DC magnet
4. can be voice modulated by using a Kerr cell
Which of these statements are correct?
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