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

1. A semiconductor region has an electric field directed from left to right. The drift directions of electrons and holes are:

2. A two-input gate gives output only when both inputs are , and gives output for all other input combinations. The gate is:

3. A table compares analog and digital circuit behaviour.

The row that is not suitable is:

4. A forward-biased diode shows only a very small current at first and then a rapid rise after a certain voltage. This happens because:

5. A pure germanium sample has no intentional impurity atoms added to it. The mobile carriers present at ordinary temperature are mainly produced by:

6. The base current in an active transistor is small mainly because:

7. A solid has a very large forbidden energy gap between its valence band and conduction band. At ordinary temperature, it will most likely behave as:

8. For a silicon - junction and a germanium - junction at ordinary temperature, the typical barrier potentials are approximately:

9. A germanium diode begins to conduct appreciably at a lower forward voltage than a silicon diode mainly because:

10. In the depletion region, electrons and holes experience forces in opposite directions under the same internal electric field because:

11. Assertion: Diffusion current in a semiconductor can exist even without an externally applied electric field.
Reason: Diffusion is caused by a carrier concentration gradient.

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

The nearly horizontal part means that:

13. A material has electrical conductivity greater than that of an insulator but smaller than that of a good conductor. The material is best classified as a:

14. A practical circuit uses a bridge rectifier, capacitor filter, and Zener regulator before feeding a digital logic circuit. The most suitable purpose of this arrangement is:

15. The truth table below belongs to which gate?

16. Assertion: In an intrinsic semiconductor, electron-hole pairs are generated in equal numbers.
Reason: Breaking one covalent bond can release one electron and leave one hole.

17. A diode is reverse biased when:

18. A safety interlock gives output only when signal and signal . The suitable Boolean expression is:

19. Under reverse bias, the depletion region of a - junction:

20. A solar cell has open-circuit voltage and delivers current at a certain operating point with terminal voltage . The output power at that operating point is:

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

22. In a silicon diode circuit, a battery, a resistor, and two forward-biased silicon diodes are in series. Taking each silicon diode drop as , the circuit current is:

23. A light-emitting diode works mainly because:

24. A newly formed - junction reaches equilibrium when:

25. A bridge rectifier uses silicon diodes and is supplied by a transformer secondary with peak voltage . If two diodes conduct in each half-cycle and each has a drop of , the approximate peak voltage across the load before filtering is:

26. Use the circuit description below.

The final output is:

27. In the reverse-bias part of a diode - characteristic, the current remains nearly constant and small before breakdown because:

28. In a Zener regulator, , , and . If rises from to , the load current ideally:

29. Assertion: Breakdown current in an ordinary diode should not be allowed to grow without limit.
Reason: Excessive current can overheat and damage the junction.

30. A claim says: “In an -type semiconductor, increasing donor concentration increases holes as the majority carriers.” The best evaluation is:

31. Use the arrangement described below.

The middle region is called the:

32. A material has equal electron and hole concentrations, but electron mobility is greater than hole mobility. Its electron contribution to conductivity is:

33. An ideal diode model is used only for a first approximation. In that model, a forward-biased diode is treated as:

34. A pure silicon crystal is considered as an intrinsic semiconductor. The word intrinsic here means that the semiconductor is:

35. A final comparison is made among three semiconductor uses: a diode rectifier, a transistor amplifier, and a logic gate. The correct shared idea is that all three:

36. A claim says: “A transistor is just two separate diodes connected back-to-back, so it should work the same way as two ordinary diodes.” The claim is:

37. A silicon sample is first intrinsic and then doped with a small amount of arsenic. After doping, its conductivity increases mainly because:

38. A solar cell is illuminated. Its open-circuit voltage is , and its short-circuit current is . When connected to a suitable load, it gives terminal voltage and current . Which statement correctly identifies the useful electrical output power?

39. In a transistor amplifier, the output signal energy ultimately comes mainly from:

40. In an active common-emitter transistor, causes . The small-signal current gain is:

41. Consider the following statements about a centre-tapped full-wave rectifier.
I. It uses two diodes in the basic circuit.
II. Each diode conducts in alternate half-cycles.
III. The load current reverses direction in every half-cycle.
The valid statements are:

42. A transistor data sheet describes the base as “lightly doped and very thin.” This design mainly reduces:

43. A logic network first sends and into an gate, then inverts the output. The final expression and gate type are:

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

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

46. A two-input gate has inputs and . Its output is:

47. A forward-biased silicon diode has across it and carries . Its static resistance at this operating point is:

48. At ordinary temperatures, the resistance of a metallic conductor generally increases when temperature rises mainly because:

49. In a two-input gate, one input changes from to while the other input remains . The output changes from:

50. A data record lists four materials.

The two entries expected to have conductor-like behaviour are: