Semiconductor Electronics-Materials, Devices and Simple Circuits Mock Test – Class 12 Physics

1. The SI unit of electric current is:

2. A silicon crystal contains one impurity atom for roughly every host atoms, and its conductivity changes noticeably. This is possible because:

3. The formation of allowed energy bands in a solid is closely connected with:

4. A material has , is doped with phosphorus, and then joined with a boron-doped region to form a junction. The most suitable sequence of ideas is:

5. When a donor atom in silicon gives up its extra electron, the donor atom becomes:

6. Assertion: The emitter and collector of a transistor are not usually interchangeable.
Reason: The emitter is heavily doped for carrier injection, while the collector is designed mainly for carrier collection and heat dissipation.

7. Dynamic resistance of a diode is especially useful because it measures:

8. When a neighbouring valence electron moves to fill a hole, the hole appears to move:

9. The reverse breakdown region of a diode - characteristic is identified by:

10. A device is needed for automatic switching of a street light when the surrounding light level changes. The most suitable semiconductor device from the given choices is:

11. Match the logic gate with its Boolean expression.

The suitable matching is:

12. A system has two sensors connected to a logic gate. The output must be only when both sensors give logic , and this output then drives an inverter. The final output is equivalent to:

13. A Zener regulator has , , and . The Zener must carry at least to regulate. The maximum load current for regulation is:

14. Use the circuit description below.

The final output is:

15. A common-emitter amplifier has , collector load , and input resistance . Ignoring phase sign for magnitude, the approximate voltage gain using is:

16. A photodiode is usually operated in reverse bias because:

17. Assertion: In active operation, a transistor can use a small base current to control a much larger collector current.
Reason: The thin base allows most carriers injected by the emitter to reach the collector.

18. When an acceptor atom accepts an electron in a silicon crystal, the acceptor atom becomes:

19. A doped semiconductor has and . The sample is best described as:

20. Read the passage below.

The process occurring near the boundary is:

21. In an unbiased - junction, the barrier potential is formed due to:

22. A diode has at , at , and at . The average dynamic resistance is smaller in:

23. A transistor has and . The values of and are closest to:

24. Drift of charge carriers in a semiconductor is caused by:

25. Study the transistor-configuration table.

The mismatched row is:

26. A rectifier connected to a source gives output pulses at . The rectifier is most likely:

27. A Zener regulator has , , , and . The minimum load current required to keep the Zener within its power rating is:

28. In the depletion region of a - junction, the charge on the -side close to the junction is mainly due to:

29. For a two-input gate, the output is only when:

30. A passage describes a modified silicon crystal.

The impurity action described here is best identified as:

31. A two-input output drives an transistor switch through a suitable base resistor. The switch turns on when . The switch turns on for:

32. A logic circuit must give output only when both of its two inputs are . The operation required is:

33. Assertion: A semiconductor can become more conducting when some electrons receive enough thermal energy to cross the forbidden gap.
Reason: Electrons in the conduction band can take part in electrical conduction.

34. Consider the following statements about carrier currents.
I. Electron motion and conventional current are in opposite directions.
II. Hole motion and conventional current are in the same direction.
III. Fixed ion motion is the main source of drift current in ordinary semiconductor conduction.
The valid statements are:

35. Use the arrangement described below.

After this electron movement, the hole is effectively located:

36. A graph of a Zener regulator output voltage versus input voltage is described below.

The nearly horizontal part means that:

37. A graph of resistance versus temperature is drawn for a semiconductor over a moderate temperature range. The expected qualitative shape is:

38. A circuit first inverts and , then sends and into a gate. The final output is:

39. A - junction is intended for controlled operation in reverse breakdown at nearly constant voltage. The most suitable device is:

40. If the barrier potential of a - junction decreases slightly when temperature increases, the most suitable qualitative reason is:

41. A hole in a semiconductor is best understood as:

42. A comparison between intrinsic and extrinsic semiconductors is made in the following table.

The mismatched row is:

43. A text-described junction has the -side on the left and the -side on the right. The depletion-region electric field is:

44. A logic circuit has output . For inputs and , the output is:

45. Study the diode-characteristic table.

The row that is not suitable is:

46. A summary claim says: “A semiconductor device can be understood fully by saying it is between a conductor and an insulator.” The strongest correction is:

47. A trivalent impurity added to a silicon crystal is called an acceptor because it:

48. In a transistor working in the active region, the dominant carriers injected from the emitter into the base are:

49. The statement “fixed ions in a doped semiconductor carry current through the crystal” is unsuitable because:

50. A relay coil requires , and a transistor with is used as a switch. The minimum base current suggested by the active-region relation is: