In this article, we published the 100 industrial electronics objective and answers for electrical and instrumentation engineers.
Industrial Electronics Objective Questions
The below list provides all the multiple-choice questions (MCQ) related to industrial electronics.
Answers are available at the bottom of the article.
1. Control system that maintains a speed voltage, or other variables within specified limits of a preset level.
| A) | Regulator |
| B) | Controller |
| C) | Computer |
| D) | Sensor |
2. An SCR combines the feature of
| A) | a rectifier and transistor |
| B) | a rectifier and resistance |
| C) | a rectifier and inductor |
| D) | a rectifier and capacitor |
3. Which transistor conducts current in both directions when turned on?
| A) | Quadrac |
| B) | Diac |
| C) | SCR |
| D) | SCS |
4. A normally operated SCR has an anode which is ______ with respect to cathode.
| A) | at zero potential |
| B) | positive |
| C) | at infinite potential |
| D) | negative |
5. When the temperature increases, the inter-base resistance of a UJT
| A) | Remains unchanged |
| B) | Decreases |
| C) | is zero |
| D) | Increases |
6. The triac is fundamentally a/an ______ with a gate terminal for controlling the turn-on conditions of the bilateral device in either direction.
| A) | SCR |
| B) | Shockley diode |
| C) | Quadric |
| D) | Diac |
7. How many semiconductor layers does a triac have?
| A) | Two |
| B) | Three |
| C) | Four |
| D) | One |
8. The voltage across an SCR when it is turned on is about
| A) | 0.5 V |
| B) | 0.1 V |
| C) | 5 V |
| D) | 1 V |
9. AC power in a load can be controlled by connecting
| A) | two SCRs in parallel opposition |
| B) | two SCRs in series opposition |
| C) | two SCRs in parallel |
| D) | two SCRs in series |
10. Which of the following is the normal way to turn on an SCR?
| A) | By appropriate gate current |
| B) | By appropriate cathode current |
| C) | By appropriate anode current |
| D) | By breakover voltage |
11. Which is the control element in an SCR?
| A) | Cathode supply |
| B) | Cathode |
| C) | Anode |
| D) | Gate |
12. What is the typical value of the interbase resistance of UJTs?
| A) | 4 KΩ |
| B) | 20 KΩ |
| C) | Between 4 to 10 KΩ |
| D) | Between 4 to 4 KΩ |
13. What Greek word which means “switch”?
| A) | Thyristor |
| B) | Ristor |
| C) | Trans |
| D) | Thy |
14. A control system in which the output is related to the input by device parameters only.
| A) | Servomechanism |
| B) | Closed-loop control system |
| C) | Open-loop control system |
| D) | Feedback control system |
15. When the emitter terminal of a UJT is open, the resistance between the base-terminals is generally
| A) | high |
| B) | extremely high |
| C) | extremely low |
| D) | low |
16. Power electronics deals with the control of ac power at what frequencies essentially?
| A) | 60 Hz frequency |
| B) | 20 KHz |
| C) | 1000 KHz |
| D) | Frequencies less than 10 Hz |
17. A feedback control system in which the controlled variable is mechanical position.
| A) | Servomechanism |
| B) | Closed-loop feedback control system |
| C) | Mechanical servomechanism |
| D) | Open-loop feedback control system |
18. An SCR is made of what material?
| A) | Germanium |
| B) | Gallium-arsenide |
| C) | Silicon |
| D) | Carbon |
19. What is basically a two-terminal parallel-inverse combination of semiconductor layers that permits triggering in either direction?
| A) | Diac |
| B) | Shockley Diode |
| C) | Quadrac |
| D) | Triac |
20. When the temperature increases, the intrinsic stand off ratio
| A) | essentially constant |
| B) | increases |
| C) | decreases |
| D) | becomes zero |
21. Which is equivalent to a zener or avalanche region of the fundamental two-layer semiconductor diode?
| A) | Breakover voltage |
| B) | Forward breakdown voltage |
| C) | Breakdown voltage |
| D) | Reverse breakdown voltage |
22. If a body is considered as a conducting sphere of 0.5m radius its capacitance to infinity is
| A) | 55 µF |
| B) | 55 nF |
| C) | 55 pF |
| D) | 55 F |
23. What are some areas where GTO is applicable?
| A) | Multivibrators |
| B) | All of the answers |
| C) | Pulse generators |
| D) | Counters |
24. What refers to the application of electronic theory, technology, instrumentation, and computing system to biological research and medical problems?
| A) | Genetics electronics |
| B) | Biomedical engineering |
| C) | Biomedical electronics |
| D) | Medical electronics |
25. The three terminals of a triac are
| A) | anode, source, gate |
| B) | two main terminals and a gate terminal |
| C) | drain, source, gate |
| D) | cathode, anode and gate |
26. The UJT may be used as
| A) | a sawtooth generator |
| B) | a multivibrator |
| C) | an amplifier |
| D) | a rectifier |
27. What is the ratio of two exponential functions of time called?
| A) | Damping ratio |
| B) | Transfer function |
| C) | Efficiency |
| D) | Gain |
28. The three terminals of an SCR are the
| A) | cathode, anode, gate |
| B) | anode, cathode, drain |
| C) | drain, source, gate |
| D) | anode, cathode, and grid |
29. What is the control element in an SCR?
| A) | Gate |
| B) | Cathode |
| C) | Grid |
| D) | Anode |
30. ECG stands for electrocardiography while EEG stands for?
| A) | electroextracellugraphy |
| B) | electroencephalography |
| C) | electroemyography |
| D) | electrovectorcardiography |
31. What are the most widely used altitude and altitude-rate transducers?
| A) | Gyro |
| B) | Flowmeter |
| C) | Gygrometer |
| D) | Psychometer |
32. An SCR is a ______ triggered device.
| A) | voltage |
| B) | noise |
| C) | current |
| D) | power |
33. In diagnostic radiology and for superficial therapy purposes, the energy spectrum of radiation varies from about
| A) | 1 to 10 KeV |
| B) | 10 to 100 KeV |
| C) | 100 to 10000 KeV |
| D) | 10000 to 100000 KeV |
34. What is that voltage above when the SCR enters the conduction region?
| A) | Forward breakover voltage |
| B) | Trigger voltage |
| C) | Reverse breakover voltage |
| D) | Holding voltage |
35. What is that value of current below which the SCR switches from the conduction state to the forward blocking region under stated conditions?
| A) | Trigger current |
| B) | Holding current |
| C) | Forward current |
| D) | Reverse current |
36. Which of the following is a four-layer diode with an anode gate and a cathode gate?
| A) | SBS |
| B) | SUS |
| C) | SCR |
| D) | SCS |
37. An SCR whose state is controlled by the light falling upon a silicon semiconductor layer of the device.
| A) | LASER |
| B) | SCS |
| C) | Thyristor |
| D) | GTO |
38. SCR is a rectifier constructed of silicon material.
Silicon is chosen because
| A) | of its strength and ruggedness |
| B) | of its high temperature and power capabilities |
| C) | it is much cheaper than any other material |
| D) | it is the most abundant material |
39. What is a nucleonic sensing method employing usually one or more radioisotope sources and radiation detectors?
| A) | Sonic level sensing |
| B) | Radiation sensing |
| C) | Dielectric variation sensing |
| D) | Conductivity level sensing |
40. What is the sensing element of the acceleration transducer?
| A) | Spring |
| B) | Damper |
| C) | Seismic mass |
| D) | Crystal |
41. An SCR is made of silicon and not germanium because silicon.
| A) | has low leakage current |
| B) | is tetravalent |
| C) | is mechanically strong |
| D) | is inexpensive |
42. When UJTs is turned on, the resistance between emitter terminal and lower base terminal
| A) | decreases |
| B) | remains unchanged |
| C) | becomes zero |
| D) | increases |
43. A locus or path of the roots traced out on the s-plane as a parameter is changed.
| A) | Parabola |
| B) | Circle |
| C) | Root locus |
| D) | Hyperbola |
44. An SCR when turned on has a typical voltage across of
| A) | infinite |
| B) | zero |
| C) | 1 V |
| D) | 0.1 V |
45. When the firing angle of SCR is increased, its output
| A) | increases |
| B) | decreases |
| C) | remains unchanged |
| D) | doubles |
46. The V-I characteristics for a triac in the first and third quadrants are essentially identical to those of ______ in the quotation.
| A) | SCS |
| B) | SCR |
| C) | UJT |
| D) | Transistor |
47. What is one of the most widely used sensing elements particularly for pressure ranges higher than 2 MPa?
| A) | Bellows |
| B) | Straight tube |
| C) | Bourdon tube |
| D) | Capsule |
48. The gate of an SCR is ______ with respect to its cathode.
| A) | positive |
| B) | at zero potential |
| C) | at infinite potential |
| D) | negative |
49. When SCR starts conducting, then ______ losses all control.
| A) | cathode |
| B) | anode |
| C) | gate |
| D) | anode supply |
50. A diac is simply
| A) | a triac without a gate terminal |
| B) | a single junction |
| C) | a three junction device |
| D) | the SCR |
51. How many pn junction does SCRs have?
| A) | Five |
| B) | Three |
| C) | Four |
| D) | Two |
52. What is dimensionless parameter of the second-order characteristic equation?
| A) | Efficiency ratio |
| B) | Transfer function ratio |
| C) | Damping ratio |
| D) | Accuracy |
53. What is a solid state equivalent of a gas filled triode?
| A) | SCS |
| B) | Thyristor |
| C) | Triac |
| D) | SCR |
54. The UJT operates in what region after peak point?
| A) | Negative resistance |
| B) | Positive resistance |
| C) | Cut off |
| D) | Saturation |
55. An SCR is a member of what family?
| A) | Thyristor |
| B) | Transistor |
| C) | Thyratron |
| D) | Thyrector |
56. A triac can pass a portion of ______ half cycle through the load
| A) | only positive |
| B) | both positive and negative |
| C) | only negative |
| D) | neither positive nor negative |
57. A triac is a _______ switch.
| A) | bidirectional |
| B) | unidirectional |
| C) | mechanical |
| D) | omnidirectional |
58. Which of the following is the normal way to turn on a diac?
| A) | By gate current |
| B) | By breakover voltage |
| C) | By anode current |
| D) | By gate voltage |
59. An effect that reduces the possibility of accidental triggering of the SCS.
| A) | End effect |
| B) | Flywheel effect |
| C) | Miller effect |
| D) | Rate effect |
60. Which device exhibits a negative resistance region?
| A) | Diac |
| B) | UJT |
| C) | Triac |
| D) | Transistor |
61. What region lies between the peak point and valley point of UJT emitter characteristics?
| A) | Saturation |
| B) | Negative resistance |
| C) | Positive resistance |
| D) | Cut off |
62. Which of the following is a common application of UJT?
| A) | Amplifier |
| B) | Rectifier |
| C) | Sawtooth generator |
| D) | Mulitivibrator |
63. A diac is turned on by
| A) | gate current |
| B) | anode current |
| C) | gate voltage |
| D) | breakover voltage |
64. An SCR is a solid state equivalent of which tube?
| A) | Gas-filled triode |
| B) | Pentode |
| C) | Tetrode |
| D) | Triode |
65. When the SCR is OFF, the current in the circuit is
| A) | exactly zero |
| B) | large leakage current |
| C) | thermal current |
| D) | small leakage current |
66. What is the other term for thermoelectric effect?
| A) | Seebeck effect |
| B) | Thermal effect |
| C) | Photoelectric effect |
| D) | Hall effect |
67. Which of the following can change the angle of conduction in SCR?
| A) | Changing anode voltage |
| B) | Changing cathode voltage |
| C) | Changing gate voltage |
| D) | Reverse biasing the gate |
68. The SCR can exercise control over ______ of ac supply.
| A) | both positive and negative half-cycles |
| B) | only negative half-cycle |
| C) | only positive half-cycle |
| D) | positive or negative half-cycle |
69. Which of the following is NOT a method primarily used for density sensing?
| A) | Radiations |
| B) | Vibrating element |
| C) | Differential |
| D) | Sonic |
70. The typical turn-off time of an SCR is about
| A) | 5 to 40 µs |
| B) | 1 to 5 µs |
| C) | 15 to 25 µs |
| D) | 20 to 40 µs |
71. What is the typical turn-on time of an SCR?
| A) | 10 µs |
| B) | 1 µs |
| C) | 3 µs |
| D) | 5 µs |
72. What device measures humidity directly with a single sensing element?
| A) | Tachometer |
| B) | Venturi meter |
| C) | Hydrometer |
| D) | Hygrometer |
73. A diac has how many terminals?
| A) | Two |
| B) | Three |
| C) | Four |
| D) | Five |
74. When an SCR is combined to a switch, it is considered as a ______ switch.
| A) | mechanical |
| B) | bidirectional |
| C) | unidirectional |
| D) | omnidirectional |
75. A triac is equivalent to two SCRs
| A) | in inverse-series |
| B) | in series |
| C) | in parallel |
| D) | in inverse-parallel |
76. To turn off the SCR, which of the following is done?
| A) | Reduce gate voltage to zero |
| B) | Reduce anode voltage to zero |
| C) | Reverse bias the gate |
| D) | Reduce cathode voltage to zero |
77. A UJT is sometimes called a _______ diode.
| A) | single-based |
| B) | double-based |
| C) | a switching diode |
| D) | a rectifier |
78. A transduction principle used primarily in optical sensors.
| A) | Photoconductive transduction |
| B) | Electromagnetic transduction |
| C) | Photovoltaic transduction |
| D) | Piezoelectric transduction |
79. To turn on the UJT, the forward bias on emitter diode should be ______ the peak point voltage.
| A) | more than |
| B) | less than |
| C) | equal to |
| D) | twice |
80. A diac is _______ switch.
| A) | a dc |
| B) | a mechanical |
| C) | an AC |
| D) | both ac and dc |
81. The step response of a first order systems is given by
| A) | y(t) = A0 + A1es1t + A2es2t + A3es3t |
| B) | y(t) = A0 + A1es1t + A2es2t |
| C) | y(t) = A0 + A1es1t |
| D) | y(t) = A0 |
82. A diac has how many semiconductor layers?
| A) | Three |
| B) | Two |
| C) | Four |
| D) | Five |
83. The p-type emitter of a UJT is ______ doped.
| A) | heavily |
| B) | moderately |
| C) | lightly |
| D) | not |
84. Acceleration transducers are also called
| A) | force transducers |
| B) | gyros |
| C) | accelerometers |
| D) | tachometers |
85. What is the required gate triggering current of GTO?
| A) | 10 mA |
| B) | 20 mA |
| C) | 40 mA |
| D) | 30 mA |
86. What sensing element is typically made from a thin-walled tube formed into deep convolutions and sealed at one end, whose displacement can then be made to act on a transduction element?
| A) | Bellow |
| B) | Bourdon tube |
| C) | Capsule |
| D) | Diaphragm |
87. How many semiconductor layers does an SCR have?
| A) | Three |
| B) | Five |
| C) | Two |
| D) | Four |
88. A diac has
| A) | three pn junctions |
| B) | four pn junctions |
| C) | two pn junctions |
| D) | one pn junction |
89. Which device does not have a gate terminal?
| A) | Diac |
| B) | Triac |
| C) | SCR |
| D) | FET |
90. What is an automatic speed control device using the centrifugal force on rotating flyweights as the feedback element?
| A) | Throttle valve |
| B) | Regulator |
| C) | Field control |
| D) | Flywheel governor |
91. Which equation defines the intrinsic stand off ratio of UJTs?
| A) | RB1/ (RB1+RB2) |
| B) | RB1+RB2 |
| C) | (RB1+RB2) / RB1 |
| D) | (RB1+RB2) / RB2 |
92. The supply voltage is generally _______ that of breakover voltage in an SCR.
| A) | twice |
| B) | greater than |
| C) | less than |
| D) | equal to |
93. The x-ray region of the electromagnetic spectrum has a corresponding range of wavelengths from
| A) | 0.1 to 0.0001 µm |
| B) | 0.1 to 0.0001 mm |
| C) | 0.1 to 0.0001 nm |
| D) | 0.1 to 0.0001 pm |
94. What is a three terminal device used to control large current to a load?
| A) | GTO |
| B) | SCS |
| C) | SCR |
| D) | Thyristor |
95. The UJT has
| A) | two pn junctions |
| B) | one pn junction |
| C) | four on junction |
| D) | three pn junctions |
96. What are the regions corresponding to open-circuit condition for the controlled rectifier which block the flow of charge from anode to cathode?
| A) | Reverse blocking regions |
| B) | Breakdown regions |
| C) | Both Forward blocking regions and Reverse blocking regions |
| D) | Forward blocking regions |
97. PUT stands for
| A) | Programmable Unijunction Transistor |
| B) | Programmable Universal Transistor |
| C) | Pulse Unijunction Transistor |
| D) | Pulse Universal Transistor |
98. What is concerned with the measurement of electric signals on the scalp with arise from the underlying neural activity in the brain (including synaptic sources)?
| A) | Ultrasound |
| B) | EKG |
| C) | ECG |
| D) | EEG |
99. When the supply voltage exceeds the breakover voltage of an SCR, it
| A) | stops conducting |
| B) | conducts leakage current |
| C) | starts conducting |
| D) | conducts terminal current |
100. In therapeutic radiology and in nuclear medicine, the energies of interest range from about
| A) | 10 to 100 KeV |
| B) | 1 to 10 KeV |
| C) | 100 to 10000 KeV |
| D) | 10000 to 10000 KeV |
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