20. An alternating current can be converted into direct current by a ____ ?

19. In forward bias, the width of potential barrier in a p − n junction diode _____ ?

18. A depletion layer consists of ?

17. Which of the following when added acts as an impurity into silicon produced n-type semiconductor ?

16. In a junction diode, the holes are due to ?

15. A semi-conducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be ?

14. The cause of the potential barrier in a p − n diode is ?

13. To obtain a p-type germanium semiconductor, it must be doped with ?

12. When arsenic is added as an impurity to silicon, the resulting material is ?

11. Which of the following, when added as an impurity, into the silicon, produces n-type semiconductor ?

10. When a p − n junction diode is reverse biased the flow of current across the junction is mainly due to ?

9. In the diagram, the input is across the terminals A and C and the output is across B and D. Then the output is ?

8. A piece of copper and other of germanium are cooled from the room temperature to 80 K, then ?

7. Diamond is very hard because ?

6. Which one of the following is the weakest kind of bonding in solids ?

5. For an electronic valve, the plate current I and plate voltage V in the space charge limited region are related as ?

4. The depletion layer in the p−n junction region is caused by ?

3. When n-type semiconductor is heated _ ?

2. p − n junction is said to be forward biased, when ?

1. At absolute zero, Si acts as :