1. Valency of silicon is

1. 4
2. 3
3. 5
4. 2

2. Overlapping of the conduction band and the valence band occurs in

1. Conductors only
2. Semiconductors only
3. Insulator only
4. Conductors and semiconductors both

3. The electron-hole mobility ratio in germanium is

1. 2 : 1
2. 1 : 1
3. (2.8) : 1
4. (1.2) : 1

4. Compared to Si, GaAs has

1. higher optoelectronic conversion efficiency
2. easier to grow crystals since the vapour pressure of arsenic is high
3. poorer crystal quality since stoichiometric growth is difficult
4. higher signal speed since electron mobility is higher

1. Statement II and IV are correct
2. Statement I and III are correct
3. Statement I and III are correct
4. Statement II and III are correct

5. Consider the following statements about conditions that make a metal-semiconductor contact rectifying

1. N-type semiconductor with its work function greater than  the work function of the metal
2. N-type semiconductor with its work function smaller than the work  function of the metal
3. P-type semiconductor with its work function greater than the work function of the metal
4. P-type semiconductor with its work function smaller than the  work function of the metal

1. Statement II and IV are correct
2. Statement I and IV are correct
3. Statement I and III are correct
4. statement II and III are correct

6. Which material has a negative temperature coefficient?

1. Brass
2. Copper
3. Aluminium
4. Carbon

7. If the temperature of a pure silicon specimen is increased then

1. Only number of free electrons increase
2. Only number of free holes increase.
3. Number of free holes and free electrons increases
4. Only number of free holes decrease

8. Under thermal equilibrium in a pure semiconductor the ratio of the number of holes to the number of conduction electrons is

1. 0.5
2. Infinity
3. 1
4. 2

9. Which of the following materials is a semiconductor?

1. Chromium
2. Selenium
3. Bismuth
4. Silica

10. In a semiconductor, the resistivity

1. Depends on temperature
2. Depends on voltage
3. Depends on current through it
4. None of the above

11. In the energy level diagram, what is the separation between the conduction band and the valence band?

1. Forbidden energy gap
2. Conduction band
3. Valence band
4. Energy band

12. The atomic number of silicon is

1. 6
2. 14
3. 22
4. 30

13. The current due to electron flow in the conduction band is

1. Less than hole current in valence band
2. Equal to hole current in valence band
3. Greater than hole current in valence band
4. Equal to hole current in conduction band

14. If the atomic number of germanium is 32, the number of electrons in the outermost shell will be

1. 2
2. 3
3. 4
4. 6

15. The ratio of reverse resistance and forward resistance of a germanium crystal diode is about

1. 1 : 1
2. 100 : 1
3. 1000 : 1
4. 40000 : 1

16. Semiconductor material has

1. Ionic bonds
2. Covalent bonds
3. Mutual bonds
4. Metallic bonds

17. A semiconductor when placed at 0 K, will act as

1. Insulator
2. Conductor
3. Semiconductor
4. Metal

18. Electronic distribution of a Si atom

1. 2,10,2
2. 2,8,4
3. 2,7,5
4. 2,4,8

19. The resistances in the higher range mostly made of

1. Carbon
2. Aluminium
3. Silicon
4. Germanium

20. According to free-electron theory, electrons in a metal are subjected to

1. Constant potential
2. Sinusoidal potential
3. Square-wave potential
4. None-periodic potential