Student Assignments Shujaat Khan-6819
Self-Test
1. The nucleus of a copper atom contains how many protons?
a. 1
b. 4
c. 18
d. 29
2. The net charge of a neutral copper atom is
a. 0
b. +1
C. —l
d. +4
3. Assume the valence electron is removed from a copper atom. The net charge of the atom becomes
a. 0
b. +1
c. —1
d. +4
4. The valence electron of a copper atom experiences what kind of attraction toward the nucleus?
a. None
b. Weak
c. Strong
d. Impossible to say
5. How many valence electrons does a silicon atom have?
a. 0
b. 1
c. 2
d. 4
6. Which is the most widely used semiconductor?
a. Copper
b. Germanium
c. Silicon
d. None of the above
7. How many protons does the nucleus of a silicon atom contain?
a. 4
b.14
c. 29
d. 32
8. Silicon atoms combine into an orderly pattern called a
a. Covalent bond
b. Crystal
c. Semiconductor
d. Valence orbit
9. An intrinsic semiconductor has some holes in it at room temperature. What causes these holes?
a. Doping
b. Free electrons
c. Thermal energy
d. Valence electrons
10. Each valence electron in an intrinsic semiconductor establishes a
a. Covalent bond
b. Free electron
c. Hole
d. Recombination
11. The merging of a free electron and a hole is called
a. Covalent bonding
b. Lifetime
c. Recommendation
d. Thermal energy
12. At room temperature an intrinsic silicon crystal acts approximately like
a. A battery
b. A conductor
c. An insulator
d. A piece of copper wire
13. The amount of time between the creation of a hole and its disappearance is called
a. Doping
b. Lifetime
c. Recombination
d. Valence
14. The valence electron of a conductor is also called a
a. Bound electron
b. Free electron
c. Nucleus
d. Proton
15. A conductor has how many types of flow?
a. 1
b. 2
c. 3
d. 4
16. A semiconductor has how many types of flow?
a. 1
b. 2
c. 3
d. 4
17. When a voltage is applied to a semiconductor, holes will flow
a. Away from the negative potential
b. Toward the positive potential
c. In the external circuit
d. None of the above
18. A conductor has how many holes?
a. Many
b. None
c. Only those produced by thermal energy
d. The same number as free electrons
19. In an intrinsic semiconductor, the number of free electrons
a. Equals the number of holes
b. Is greater than the number of holes
c. Is less than the number of holes
d. None of the above
20. Absolute zero temperature equals
a. —273°C
b. 0°C
c. 25°C
d. 50°C
21. At absolute zero temperature an intrinsic semiconductor has
a. A few free electrons
b. Many holes
c. Many free electrons
d. No holes or free electrons
22. At room temperature an intrinsic semiconductor has
a. A few free electrons and holes
b. Many holes
c. Many free electrons
d. No holes
23. The number of free electrons and holes in an intrinsic semiconductor increases when the temperature
a. Decreases
b. Increases
c. Stays the same
d. None of the above
24. The flow of valence electrons to the left means that holes are flowing to the
a. Left
b. Right
c. Either way
d. None of the above
25. Holes act like
a. Atoms
b. Crystals
c. Negative charges
d. Positive charges
26. Trivalent atoms have how many valence electrons?
a. 1
b. 3
c. 4
d. 5
27. A donor atom has how many valence electrons?
a. 1
b. 3
c. 4
d. 5
28. If you wanted to produce a p-type semiconductor, which of these would you use?
a. Acceptor atoms
b. Donor atoms
c. Pentavalent impurity
d. Silicon
29. Holes are the minority carriers in which type of semiconductor?
a. Extrinsic
b. Intrinsic
c. n-type
d. p-type
30. How many free electrons does a p-type semiconductor contain?
a. Many
b. None
c. Only those produced by thermal energy
d. Same number as holes
31. Silver is the best conductor. How many valence electrons do you think it has?
a. 1
b. 4
c. 18
d. 29
32. Suppose an intrinsic semiconductor has 1 billion free electrons at room temperature. If the temperature changes to 75°C, how many holes are there?
a. Fewer than 1 billion
b. 1 billion
c. More than 1 billion
d. Impossible to say
33. An external voltage source is applied to a p-type semiconductor. If the left end of the crystal is positive, which way do the majority carriers flow?
a. Left
b. Right
c. Neither
d. Impossible to say
34. Which of the following doesn’t fit in the group?
a. Conductor
b. Semiconductor
c. Four valence electrons
d. Crystal structure
35. Which of the following is approximately equal to room temperature?
a. 0°C
b. 25°C
c. 50°C
d. 75°C
36. How many electrons are there in the valence orbit of a silicon atom within a crystal?
a. 1
b. 4
c. 8
d. 14
37. Positive ions are atoms that have
a. Gained a proton
b. Lost a proton
c. Gained an electron
d. Lost an electron
38. Which of the following describes an n-type semiconductor?
a. Neutral
b. Positively charged
c. Negatively charged
d. Has many holes
39. A p-type semiconductor contains holes and
a. Positive ions
b. Negative ions
c. Pentavalent atoms
d. Donor atoms
40. Which of the following describes a p-type semiconductor?
a. Neutral
b. Positively charged
c. Negatively charged
d. Has many free electrons
41. Which of the following cannot move?
a. Holes
b. Free electrons
C. Ions
d. Majority carriers
42 What causes the depletion layer?
a. Doping
b. Recombination
c. Barrier potential
d. Ions
43. What is the barrier potential of a silicon diode at room temperature?
a. 0.3 V
b. 0.7 V
c.1V
d. 2 mV per degree Celsius
44. To produce a large forward current in a silicon diode, the applied voltage must be greater than
a.0
b. 0.3 V
c. 0.7 V
d.1V
45. In a silicon diode the reverse current is usually
a. Very small
b. Very large
c. Zero
d. In the breakdown region
46. Surface-leakage current is part of the
a. Forward current
b. Forward breakdown
c. Reverse current
d. Reverse breakdown
47. The voltage where avalanche occurs is called the
a. Barrier potential
b. Depletion layer
c. Knee voltage
d. Breakdown voltage
48. Diffusion of free electrons across the junction of an unbiased diode produces
a. Forward bias
b. Reverse bias
c. Breakdown
d. The depletion layer
49. When the reverse voltage increases from 5 to 10 V, the depletion layer
a. Becomes smaller
b. Becomes larger
c. Is unaffected
d. Breaks down
50. When a diode is forward-biased, the recombination of free electrons and holes may produce
a. Heat
b. Light
c. Radiation
d. All of the above
51. A reverse voltage of 20 V is across a diode. What is the voltage across the depletion layer?
a. 0 V
b. 0.7 V
c. 20 V
d. None of the above
52. Each degree rise in junction temperature decreases the barrier potential by
a. 1 mV
b. 2 mV
c. 4 mV
d. lOmV
53. The reverse saturation current doubles when the junction temperature increases
a. 1°C
b. 2°C
c. 4°C
d. 10°C
54. The surface-leakage current doubles when the reverse voltage increases
a. 7%
b. 100%
c. 200%
d. 2 mV
