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Advanced Maintenance Electrician Review Questions I. Multiple-choice Questions: 1. In the DC circuit shown in the figure, I1 is ( ) A. (A) 11 (B) –5 (C) 15 (D) 5 2. In the inter-stage coupling of multi-stage amplification circuits, low-frequency voltage amplification circuits should use only ( ) coupling method. (A) Capacitor-resistor (B) Direct (C) Transformer (D) Inductor 3. There is a special substance surrounding the magnetic poles; this substance possesses properties of force and energy, and it is called ( ). (A) Magnetism (B) Magnetic field (C) Magnetic force (D) Magnet 4. In a magnetic circuit ( ). (A) Where there is magnetic reluctance, there must be magnetic flux. (B) Where there is magnetic flux, there must be magnetic flux density. (C) Where there is magnetic flux density, there must be magnetic flux. (D) The greater the permeability, the greater the magnetic reluctance. 5. In a magnetic circuit with constant permeability, when the magnetic flux density is 5 ampere-turns, the magnetic flux is 1 weber ； When the magnetic flux linkage is 10 ampere-turns, the magnetic flux is ( ) Wb. (A) 2.5 (B) 10 (C) 2 (D) 5 6. When a conductor is placed in a magnetic field and perpendicular to the magnetic field lines, the electromotive force generated in the conductor is greatest when the direction of motion of the conductor forms an ( ) angle with the direction of the magnetic field lines. (A) 90 (B) 30 (C) 45 (D) 0 7. The magnitude of the self-induced emf in a coil is independent of ( ). (A) The rate of change of current in the coil (B) The number of turns in the coil (C) The medium surrounding the coil (D) The resistance of the coil. 8. The polarity of a transformer coil is generally determined based on ( ). (A) Right-hand rule (B) Left-hand rule (C) Lenz’s law (D) Like poles 9. The core of a transformer is made up of stacked insulated silicon steel sheets; the main purpose of this is ( ). (A) Reduce magnetic resistance and stray losses (B) Reduce magnetic resistance and copper losses (C) Reduce magnetic resistance and resistance (D) Reduce magnetic resistance and iron losses 10. With the current in the electromagnet coil remaining constant, as the armature is attracted, the magnetic flux in the core will ( ). (A) Increase (B) Decrease (C) Remain unchanged (D) Unable to determine 11. The JSS-4A crystal transistor tester is a common instrument used to measure the h-parameter and ( ) of medium and low-power crystal transistors at low frequencies. (A) Breakdown voltage (B) Dissipation power (C) Saturation current (D) Frequency characteristics. 12. The DC amplifier in the JSS-4A transistor h-parameter tester uses a （ ） amplifier. (A) AC (B) Pulse (C) Differential (D) Power 13. When observing the forward characteristics of a diode using a transistor tester, one should ( ). (A) The switch for the X-axis is set to collector voltage, and the switch for the Y-axis is set to collector current. (B) The switch for the X-axis is set to collector voltage, and the switch for the Y-axis is set to base current. (C) The switch for the X-axis is set to base voltage, and the switch for the Y-axis is set to base current. (D) The switch for the X-axis is set to base voltage, and the switch for the Y-axis is set to collector current. 14. When using an ordinary SB-10 oscilloscope to observe signal waveforms, to make the displayed waveform stable, it is possible to adjust the ( ) knob. (A) Focus (B) Step gain (C) Auxiliary focus (D) Brightness 15. The “Brightness” knob on the oscilloscope panel is the potentiometer used to adjust ( ). (A) Control gate negative voltage (B) Control gate positive voltage (C) Cathode negative voltage (D) Cathode positive voltage. 16. In the SR-8 dual-trace oscilloscope, “DC–⊥–AC” is the selection switch for the coupling method by which the signal to be measured is fed back to the oscilloscope’s input terminal. When this switch is set to the “⊥” position, it indicates ( ). (A) The input terminal is grounded. (B) The instrument should be placed vertically. (C) The input terminal can conduct direct current. (D) The input terminal can conduct alternating current. 17. The electronic switch in the SR-8 dual-trace oscilloscope has ( ) operating states. (A) 2 (B) 3 (C) 4 (D) 5 18. The main factor that affects the stability of the quiescent operating point in an analog amplification circuit is ( ). (A) The β value of the transistor (B) The saturation current of the transistor (C) The frequency of the amplified signal (D) The temperature of the operating environment. 19. A capacitive three-point sine wave oscillator belongs to which type of oscillation circuit? (A) RC (B) LC (C) RL (D) Quartz crystal 20. A DC differential amplification circuit can ( ) (A) Amplify the common-mode signal and suppress the differential-mode signal (B) Amplify the differential-mode signal and suppress the common-mode signal (C) Amplify both the differential-mode and common-mode signals (D) Suppress both the differential-mode and common-mode signals 21. An integrated operational amplifier is a type of amplifier with ( ) coupling. (A) Capacitance resistance at high magnification (B) Capacitance resistance at low magnification (C) Direct connection at high magnification (D) Direct connection at low magnification. 22. In a silicon Zener diode circuit, the function of the current-limiting resistor R is ( ). (A) Both current limiting and voltage reduction (B) Both current limiting and voltage regulation (C) Both voltage reduction and voltage regulation (D) Both voltage regulation and current limiting] 23. The logical function of a NAND gate is ( ). (A) 0 input, 0 output; 1 input, 1 output. (B) 1 input, 0 output; 0 input, 0 output. (C) 0 input, 1 output; 1 input, 0 output. (D) 1 input, 0 output; 0 input, 1 output. 24. When all the input terminals of a TTL NAND gate are left unconnected at the same time, what is the output? (A) Zero level (B) Low level (C) High level (D) It may be either low level or high level. 25. In an OR-NOT gate flip-flop, when R=S=1, the state of the flip-flop is ( ). (A) Set to 1 (B) Set to 0 (C) Remain unchanged (D) Indeterminate. 26. The oscillation frequency of a TTL NAND gate RC ring oscillator is determined by ( ). (A) The number of TTL NAND gates (B) The value of the resistor R (C) The capacitance of capacitor C (D) RC 27. For an asynchronous three-bit binary addition counter, what is the state of the counter after the eighth CP pulse? (A) 000 (B) 010 (C) 110 (D) 101 28. Registers are mainly composed of ( ). (A) Flip-flop (B) Gate circuit (C) Oscillator (D) Flip-flop and gate circuit 29. The most commonly used display device is a ( ) digital display. (A) Five segments (B) Seven segments (C) Nine segments (D) Eleven segments 30. In a three-phase half-controlled bridge rectifier circuit, the phase difference between the trigger pulses of the common-cathode thyristors is required to be ( ). (A) 60 (B) 120 (C) 150 (D) 180 31. In a simple reverse-blocking thyristor chopper, （ ） thyristors are used. (A) Only one (B) Two main ones (C) Two auxiliary ones (D) One main thyristor and one auxiliary one. 32. In a parallel resonant thyristor inverter, in order to achieve a higher power factor and efficiency, the frequency of the thyristor trigger pulses should be ( ) the resonance frequency of the load circuit. (A) Much greater than (B) Greater than (C) Close to (D) Less than 33. The power field-effect transistor MOSFET is an ideal ( ) control device. (A) Voltage (B) Current (C) Resistance (D) Power 34. In a chopper, if a thyristor is used as the main switching device in place of a power thyristor, then ( ). (A) Reduce volume (B) Reduce weight (C) Increase loss (D) Decrease loss 35. In power electronic devices, power transistors generally operate in the ( ) state. (A) Amplification (B) Cutoff (C) Saturation (D) Switching 36. When using power transistors, it is necessary to prevent ( ). (A) Secondary breakdown (B) Electrostatic breakdown (C) Failure due to prolonged use (D) Operating in switching mode 37. The switching frequency of power thyristors is ( ) that of power field-effect transistors. (A) Slightly higher than (B) Lower than (C) Significantly higher than (D) Equal to 38. The interior of a insulated gate bipolar transistor has a ( ) layer structure. (A) 1 (B) 2 (C) 3 (D) 4 39. Insulated gate bipolar transistor ( ) circuit. (A) Special forced commutation is not necessary. (B) Special forced commutation can be used. (C) Special forced commutation is necessary. (D) Special forced commutation can be used. 40. When using a signal generator and an oscilloscope to observe the waveform of an amplification circuit, in order to avoid unnecessary induction and interference between the enclosures of the instruments, it is necessary to connect the grounding terminals of all instruments ( ). (A) Together. (B) With insulation between them. (C) Left ungrounded. (D) Grounded separately. 41. The core of a transformer is mostly composed of ( ). (A) 2 (B) 3 (C) 4 (D) 5 42. The repair steps for a breakdown in the main insulation of a transformer are: replacing the insulation, drying the transformer body, and ( ). (A) Binding (B) Filling with a qualified transformer core (C) Welding the leads (D) Repairing the grounding plates. 43. After the repair and assembly of a wound-rotor asynchronous motor, it is necessary to perform certain actions on the brushes. (A) Replacement (B) Grinding (C) Tuning (D) Heat treatment 44. The main component of a DC motor rotor is ( ) (A) Armature (B) Main magnetic pole (C) Commutator pole (D) Brush 45. In emergency handling of an open-circuit fault in a DC motor, among the wave-wound components, cross-wired wires can be used to connect the two commutator segments of the component with an open circuit; these commutator segments are those of ( ). (A) Adjacent (B) One pitch apart (C) Two pitches apart (D) Three pitches apart. 46. The methods for checking transformer faults are generally divided into ( ) types. (A) 2 (B) 3 (C) 4 (D) 5 47. After maintenance on transformers with a voltage of 0.4 kV or less, it is generally required that the insulation resistance be no lower than ( ). (A) 0.5M (B) 90M (C) 200M (D) 220M 48. Three-phase asynchronous motors operate on the principle of ( ). (A) A conductor cutting magnetic field lines (B) The magnetic field generated by a coil of current (C) A current-carrying conductor moving under the force in a magnetic field (D) Electromagnetic induction and a current-carrying conductor under force in a magnetic field. 49. The commutator winding of a DC motor must be ( ) with the armature winding. (A) Series (B) Parallel (C) Perpendicular (D) Opposite flux direction. 50. There are ____ aspects to the reason why the output voltage of a shunt generator decreases as the load current increases. (A) 2 (B) 3 (C) 4 (D) 5 51. When a three-phase asynchronous motor is used for reverse braking, a symmetric resistor connection is employed; this allows for the limitation of the braking torque while also limiting ( ). (A) Braking current (B) Starting current (C) Braking voltage (D) Starting voltage 52. There are ( ) types of DC tachogenerators based on their excitation method. (A) 2 (B) 3 (C) 4 (D) 5 53. The rotor of an AC servo motor is usually designed in a ( ) shape. (A) Shaded pole (B) Salient pole (C) Wound rotor (D) Squirrel-cage 54. Control-type synchroscopes are classified into （ ） types according to their uses. (A) 3 (B) 2 (C) 4 (D) 5 55. The step angle θ of a reaction-type stepper motor is proportional to the number of rotor teeth Zr ( ). (A) Directly proportional (B) Inversely proportional (C) Proportional to the square of (D) Inversely proportional to the square of 56. The working principle of a DC torque motor is the same as that of a （ ） motor. (A) Ordinary DC servo (B) Asynchronous (C) Synchronous (D) Stepper 57. What are the structural characteristics of an induction intermediate-frequency generator? (A) An excitation winding is installed on the stator, while an armature winding is installed on the rotor. (B) There are no windings on either the stator or the rotor. (C) An excitation winding and an armature winding are installed on the stator, while there are no windings on the rotor. (D) An armature winding is installed on the stator, while an excitation winding is installed on the rotor. Archangel: 2005-6-24 12:03:00 58. The mechanical characteristics of a slip motor depend mainly on the mechanical characteristics of ( ). (A) Asynchronous motor (B) Slip clutch (C) Tachogenerator (D) Combination of asynchronous motor and tachogenerator 59. When a cross-magnetic motor amplifier is operating normally, its compensation level is ( ). (A) Full compensation (B) Slightly under-compensation (C) Over-compensation (D) No compensation 60. In the cascade speed control circuit of a wound-rotor asynchronous motor, it is necessary to have （） in the rotor circuit. (A) Series additional resistance (B) Series additional electromotive force (C) Parallel additional resistance (D) Parallel additional electromotive force. 61. The speed control principle of an AC commutator motor is （） speed control. (A) Frequency conversion (B) Weak magnetization (C) Introduction of an adjustable potential Ek in the motor stator auxiliary winding (D) Changing the number of pole pairs of the motor by altering the wiring of the stator windings. 62. The method that uses a rotor position detector mounted on the motor shaft to control the trigger pulses of the frequency conversion circuit is called (). (A) Externally controlled amplitude variation (B) Internally controlled amplitude variation (C) Externally controlled frequency variation (D) Internally controlled frequency variation. 63. A wound-rotor asynchronous motor can achieve ( ) using cascade speed control. (A) Stepless speed control (B) Continuous speed control (C) Softening of mechanical characteristics (D) Simplification of the circuit. 64. Speed control of three-phase shunt-wound commutator motors is suitable for （ ） loads. (A) Constant torque (B) Gradually increasing torque (C) Constant power (D) Gradually decreasing torque 65. In the basic circuit of a brushless motor, when the motor is operating in regenerative braking mode, the inverter circuit operates in ( ) mode. (A) Inversion (B) Amplification (C) Chopping (D) Rectification 66. The inverter used in variable-frequency speed control is generally composed of ( ). (A) Rectifier, filter, inverter (B) Amplifier, filter, inverter (C) Rectifier, filter (D) Inverter 67. During the process of adjusting the speed of a DC motor using a chopper, (). (A) There is additional energy loss. (B) There is no additional energy loss. (C) The magnetic field will be weakened. (D) The magnetic field will be strengthened. 68. In an open-loop automatic control system, what will happen when a deviation occurs? (A) Cannot eliminate the deviation (B) Can completely eliminate the deviation (C) Can eliminate one-third of the deviation (D) Can eliminate half of the deviation. 69. The speed control system with negative feedback has a compensatory capability for the speed reduction caused by the sensing feedback element and the set voltage. (A) None (B) Yes (C) It has the ability to compensate for the former, but not for the latter (D) It has no ability to compensate for the former, but can compensate for the latter. 70. A voltage negative feedback speed control system achieves stable rotation speeds by stabilizing the armature voltage of a DC motor; the principle behind this is that changes in the armature voltage are related to ( ). (A) The change in speed is proportional. (B) The change in speed is inversely proportional. (C) The change in speed is proportional to the square of the value. (D) The change in speed is inversely proportional to the square of the value. 71. When the load increases, the speed compensation resulting from current positive feedback actually leads to an increase in speed, rather than a decrease in it. (A) Rising (B) Falling (C) Rising for a while then falling (D) Falling for a while then rising 72. The cutoff method in current-cutoff negative feedback can be achieved not only through voltage comparison but also by connecting a ( ) in the feedback loop. (A) Thyristor (B) Triode (C) Unijunction transistor (D) Zener diode 73. For a magnetic scale, the parameters include dynamic range, accuracy, and resolution; among these, the dynamic range is ( ). (A) 1m-40m (B) 1m-10m (C) 1m-20m (D) 1m-50m 74. The position controller within the CNC device, upon receiving control commands, is used to control the machine tool ( ). (A) Feeding (B) Spindle speed change (C) Oil pump activation (D) Tool changer in the tool magazine 75. ( ) belongs to contour control CNC machines. (A) CNC lathe (B) CNC drilling machine (C) Machining center (D) CNC boring machine 76. The automated integrated control system includes two aspects: ( ). (A) Sequential control and digital control (B) Sequential control and feedback control (C) Analog control and digital control (D) Feedback control and digital control 77. Simple automated assembly lines generally use （） control. (A) Sequential control (B) Feedback control (C) Sequential control for the front part, with feedback control for the rear part (D) Feedback control for the front part, sequential control for the rear part. 78. The operating speed of AC two-speed elevators should generally be less than ( ) m/s. (A) 1 (B) 2 (C) 2.5 (D) 3 79. The armature circuit of a DC elevator of type (SCR-C) is powered by two sets of three-phase full-wave controlled rectifiers connected in reverse parallel. When the control angle α of the forward rectifier bridge (ZCAC) is 90, the control angle α of the reverse rectifier