Exercises

MCQs about electronics

1. Valence electrons are
a) in the closest orbit to b) in the most distant orbit c) in various orbits around d) not associated with a
the nucleus. from the nucleus the nucleus particular atom
2. The number of electrons in the valence band in a silicon atom is
a) 8 b) 5 c) 4 d) 3
3. A positive ion is formed when
a) a valence electron b) there are more holes c) an atom gains an extra d) two atoms bond
breaks away from the than electrons in the valence electron together
atom outer orbit
4. Electron-hole pairs are produced by
a) recombination b) thermal energy c) ionization d) doping

5. In an intrinsic semiconductor,
a) there are no free b) the free electrons are c) there are only holes d) answers (b) and (c)
electrons thermally produced
6. The energy band in which free electrons exist is the
a) first band b) second band c) conduction band d) valence band

7. Recombination is when
a) an electron falls into a b) a positive and a negative c) a valence electron d) a crystal is formed
hole ion bond together becomes a conduction
electron
8. An atom consists of
a) one nucleus and only b) one nucleus and one or c) protons, electrons, and d) answers (b) and (c)
one electron more electrons neutrons
9. The atomic number of germanium is
a) 13 b) 30 c) 31 d) 32

10. The nucleus of an atom is made up of

a) protons and neutrons b) electrons c) electrons and protons d) electrons and neutrons

11. The atomic number of silicon is

a) 13 b) 14 c) 8 d) 15

12. Every known element has

a) the same type of b) the same number of c) a unique of atom d) several different types
atoms atoms of atoms
13. In a semiconductor crystal, the atoms are held together by
a) the interaction of b) forces of attraction c) covalent bonds d) answers (a), (b), and (c)
valence electrons
14. The purpose of a pentavalent impurity is to
a) reduce the b) increase the number of c) increase the number of d) create minority carriers
conductivity of silicon holes free electrons

15. A p-n junction is formed by

a) the recombination of b) ionization c) the boundary of a p- d) the collision of a proton
electrons and holes type and an n-type and a neutron
material
16. The process of adding an impurity to an intrinsic semiconductor is called
a) doping b) recombination c) atomic modification d) ionization

17. A trivalent impurity is added to silicon to create

a) germanium b) a p-type semiconductor c) an n-type d) a depletion region
semiconductor
18. Holes in an n-type semiconductor are
a) minority carriers that b) minority carriers that are c) majority carriers that d) majority carriers that
are thermally produced by doping are thermally produced are produced by doping
produced
19. The current in a semiconductor is produced by
a) electrons only b) holes only c) negative ions d) both electrons and holes

20. Each atom in a silicon crystal has

a) four valence electrons b) four conduction electrons c) eight valence electrons, d) no valence electrons
four of its own and four because all are shared
shared with other atoms
21. The difference between an insulator and a semiconductor is
a) a wider energy gap b) the number of free c) the atomic structure d) answers (a), (b), and (c)
between the valence electrons
band and the
conduction band
22. The majority carriers in an n-type semiconductor are
a) holes b) valence electrons c) conduction electrons d) protons

23. The minority carriers in an p-type semiconductor are

a) holes b) valence electrons c) conduction electrons d) protons

24. The depletion region consists of

a) nothing but minority b) no majority carriers c) positive and negative d) answers (b) and (c)
carriers ions
25. When a diode is forward-biased,
a) the only current is b) the only current is c) the only current is d) the current is produced
hole current electron current produced by majority by both holes and
carriers electrons
26. To forward-bias a diode, an external voltage is applied that is positive at …… and negative at….
a) the anode, the cathode b) the cathode, the anode c) the p-region, the n-region d) both (a) and (c)

27. The term bias means

a) the ratio of majority b) the amount of current c) a dc voltage is applied d) neither (a), (b), nor (c)
carriers to minority across a diode to control the
carriers operation of a device

28. The depletion region is created by

a) ionization b) diffusion c) recombination d) answers (a), (b), and (c)

29. Although current is blocked in reverse bias,

a) there is some current b) there is a very small c) there is an avalanche d) there is no current
due to majority current due to minority current
carriers carriers
30. For a germanium diode, the value of the forward-bias voltage typically
a) must be greater than b) must be greater than c) depends on the width d) depends on the
0.3V 0.7V of the depletion region concentration of
majority carriers
31. The positive lead of an ohmmeter is connected to the anode of a diode and the negative lead is
connected to the cathode. The diode is
a) reversed-biased b) open c) forward-biased d) answers (b) and (c)

32. When forward-biased, a diode

a) blocks current b) conducts current c) has a high resistance d) drops a large voltage

33. For a silicon diode, the value of the forward-bias voltage typically
a) must be greater than b) must be greater than 0.7 c) depends on the width d) depends on the
0.3 V V of the depletion region concentration of
majority carriers
34. A silicon diode is in series with a 1.0 kΩ resistor and a 5 V battery. If the anode is connected to the
positive battery terminal, the cathode voltage with respect to the negative battery terminal is
a) 0.7 V b) 0.3 V c) 5.7 V d) 4.3 V
35. When a voltmeter is placed across a forward-biased diode, it will read a voltage approximately
equal to
a) the bias battery b) 0 V c) the diode barrier d) the total circuit voltage
voltage potential
36. A practical silicon diode in series with a 1.0 kΩ resistor and a 5 V battery. If the diode is forward
biased, what is the voltage across the resistor
a) 0.7 V b) 0.3 V c) 5.7 V d) 4.3 V
37. In case of unbiased diode, when a p-type connects to n-type and a depletion region is created, then
positively charged ions are build-up in
a) n-region b) p-region c) ohmic region d) answers (a) and (c)

38. when heat is add to silicon…… are produced

a) electrons b) holes c) atoms d) answers (a) and (b)

39. An LED
a) emits light when b) senses light when c) emits light when d) acts as a variable
reverse-biased reverse-biased forward-biased resistance
40. Compared to a visible red LED, an infrared LED
a) produces light with b) produces light of all c) produces only one d) produces light with
shorter wavelengths wavelengths color of light longer wavelengths
 41. Difference between normal diode and Zener,
a) zener is lightly doped b) zener is heavily doped c) zener can conduct in d) answers (b) and (c)
forward bias
42. An ideal Zener diode is reverse-biased in series with 9V battery and 2kΩ resistor, if Vz=3V, what
is the current intensity value in the circuit
a) 0 mA b) 1.5 mA c) 3 mA d) 4.5 mA
43. An ideal silicon diode in series with a 2.0 kΩ resistor and a 9 V battery. If the diode is forward
biased, what is the voltage across the resistor
a) 0 V b) 4.5 V c) 8.3 V d) 9 V
44. In the half wave rectifier using Si diode, if the peak input voltage is 5V, what is the peak output
voltage
a) 5 V b) 4.3 V c) 3.6 V d) 4.7 V
45. In the full wave rectifier using Si diode, if the peak input voltage is 5V, what is the peak output
voltage
a) 5 V b) 4.3 V c) 3.6 V d) 4.7 V
46. An ideal silicon diode in series with a 2.0 kΩ resistor and a 9 V battery. If the diode is reverse
biased, what is the current across the resistor
a) 0 mA b) 1.5 mA c) 3 mA d) 4.5 mA

47. Holes concentration equal to electrons concentration in

a) conductors b) insulators c) intrinsic semiconductors d) extrinsic semiconductors

48. When p-type semiconductor is in contact with n-type semiconductor, ……... is formed
a) a depletion region b) space-charge c) transition region d) answers a, b, and c
49. If you are checking a 60 Hz full-wave bridge rectifier and observe that the output ha a 60 Hz
ripple,
a) the circuit is working b) there is an open diode c) the transformer d) the filter capacitor is
properly secondary is shorted leaky
50. With increasing the temperature, the resistance of the intrinsic semiconductors…
a) increase b) decrease c) remain the same d) temperature independent

51. In case of the half wave rectifier, what is the output frequency if the input frequency is 60 Hz?
a) 30 Hz b) 60 Hz c) 90 Hz d) 120 Hz

52. If the ripple voltage is 1.13 V and the DC voltage is 14.3 V, what is the ripple factor percentage
a) 12.65 b) 0.079 c) 7.9% d) 12.65%

53. The average value of a half-wave rectified voltage with a peak value of 200 V is
a) 63.7 V b) 127.3 V c) 199.3 V d) 198.6 V
54. When the peak value of the input to a half-wave rectifier is 10 V, the diode must be able to
withstand a reverse voltage of
a) 10 V b) 9.3 V c) 8.6 V d) 20 V

55. The average value of a full wave rectified voltage with a peak value of 75 V is
a) 75 V b) 73.6 V c) 74.3 V d) 47.8 V
56. A certain power-supply filter produces an output with a ripple of 100 mV peak-to-peak and a dc
value of 20 V. The ripple factor is
a) 5 b) 0.2 c) 0.05 d) 200

57. A 60 V peak full-wave rectified voltage is applied to a capacitor-input filter. If f= 120 Hz, RL = 10
kΩ, and C = 10 μF, the ripple voltage is
a) 0.6 V b) 6 mV c) 5 V d) 2.88 V
58. A 60 V peak full-wave rectified voltage is applied to a capacitor-input filter. If f= 120 Hz, RL = 10
kΩ, and C = 10 μF, the output DC voltage is
a) 58.6 V b) 57.5 V c) 59.3 V d) 60 V

59. If the load resistance of a capacitor-filtered full-wave rectifier is reduced. the ripple voltage
a) increases b) decreases c) is not affected d) has a different frequency

60. If one of the diodes in a bridge full-wave rectifier opens, the output is
a) 0 V b) one-fourth the amplitude c) a half-wave rectified d) a 120 Hz voltage
of the input voltage voltage
61. If a certain zener diode has a zener voltage of 3.6 V, it operates in
a) regulated breakdown b) zener breakdown c) Forward conduction d) avalanche breakdown
62. For a certain 12 V zener diode. a 10 mA change in zener current produces a 0.1 V change in zener
voltage. The zener impedance for this current range is
a) 0.1 Ω b) 1 Ω c) 10 Ω d) 100 Ω

63. The data sheet for a particular zener gives Vz = 10 V at IZT = 500 mA. Zz for these conditions is
a) 50 Ω b) 20 Ω c) 10 Ω d) unknown
64. Three ideal diodes are connected to the battery as shown in the circuit. The current supplied by
the battery is

a) 0A b) 4A c) 2A d) 6A

65. When a p-n junction is forward biased, then

a) The depletion region b) The p-side is at higher c) The current flowing is d) The effective resistance
become thick potential than n-side zero is of the order of 106 Ω
66. If the frequency of the input voltage in the circuit is increased, the output frequency will……

a) increased b) decreased c) not changed d) the same as input

67. The current through an ideal p-n junction diode shown in the circuit will be ……
a) 5 A b) 0.2 A c) 0.6 A d) 0 A
68. The given circuit has two ideal diodes connected as shown in the figure below. The current flowing
through the resistance R1 will be……

a) 5 A b) 2.5 A c) 10 A d) 3.13 A

69. Which one of the following statements is false?

a) Pure Si doped with b) Majority carriers in a n- c) Minority carriers in a p- d) The resistance of intrinsic
trivalent impurities gives type semiconductor are type semiconductor are semiconductor decreases
a p-type semiconductor. holes. electron. with temperature.
70. PN-junction diode works as a insulator, if connected
a) To A.C. b) In forward biased c) In reverse biased d) None of these

71. On increasing the reverse bias to a large value in a PN-junction diode, current
a) Increases slowly b) Remain fixed c) Suddenly increases d) Decrease slowly

72. In a junction diode, the holes are due to

a) Protons b) Neutrons c) Extra electrons d) Missing of electrons
73. Which is the correct diagram of a half-wave rectifier?

a) 1. b) 2. c) 3. d) 4.

74. Zener breakdown takes place if

a) Doped impurity is less b) Doped impurity is high c) Less impurity in n-type d) Less impurity in p-type