First, yes and no questions
1. The indicating instrument can not only directly measure the electromagnetic quantity, but also can cooperate with various sensors to measure the non-electric quantity such as temperature, pressure and flow. (√)
2. In addition to the current meter and voltmeter, which can be used for both DC and high accuracy, the electric instrument can also be made into a power meter, a frequency meter and a phase meter. (√)
3. For instruments with an accuracy of 1.5, the basic error of measurement is ± 3%. (×)
4, to directly measure the average value of the current in the circuit, you can use the electromagnetic system. (×)
5, the additional resistance of the voltmeter can also expand the range, but also play a temperature compensation role. (√)
6. The secondary winding of the voltage transformer is not allowed to open, and the secondary winding of the current transformer is not allowed to be short-circuited. (×)
7. The DC ammeter can be used in AC circuits. (×)
8. The clamp ammeter can be made to measure both AC current and DC current. (√)
9. Use a multimeter to measure the resistance. You must adjust the pointer once every time you change the ohms. (√)
10. When measuring AC circuit and active energy, because it is AC, its voltage coil, current coil and each end can be connected to the line. (×)
11. When two-phase three-wire active load energy is measured by two single-phase electric energy meters, there is a table reversal, which is definitely a wiring error. (×)
12, the current coil of the electric power meter will reverse the deflection of the pointer, but if the voltage coil is also reversed, it can operate normally. (×)
13. The resistance of the electromagnetic system to the external magnetic field is stronger than that of the magnetoelectric system. (×)
14. The electric system phase meter has no hairspring that generates a reaction torque, so the pointer can stop at any position on the dial before the meter is connected to the circuit. (√)
15. According to the instrument's defense ability against electric field or external magnetic field, it is divided into four levels: I, II, III and IV. Class II meters are allowed to change their indication value by ± 1% under the influence of an external magnetic field or an external electric field. (√)
16. The larger the internal resistance of the ammeter that measures the current, the better. (×)
17. The multimeter's ohmmeter is not available to directly measure the internal resistance of the micro-ampere meter, galvanometer or standard battery. (√)
18, whether it is measuring direct current or alternating current, the illumination of the xenon lamp of the electroscope is the same. (×)
19. A low-voltage electroscope equipped with a neon bulb can distinguish between a live line (phase line) and a ground line, and can also detect alternating current or direct current. The digital display can detect the presence or absence of electricity in addition to the low-voltage electroscope. Line. (√)
20, wire stripper can be used to strip the insulation of plastic wire or rubber wire with a core area of ​​6mm2 or less, so there should be a cut of 6mm or less in diameter. (×)
21, the protection terminal of the soldering iron can be wired or not. (×)
22, manual hydraulic crimping pliers can be used to crimp copper and aluminum wires with a cross section of 16~240mm2. (√)
23, when installing the grounding wire, first install the three-phase line end, and then install the grounding end; when disassembling, reverse the grounding end first, then remove the three-phase line end. (×)
24, the length of the first and second wiring of the welding machine should not exceed 20m. (×)
25, AC current meter and voltmeter indicate all valid values. (√)
26, insulated boots can also be used as acid, alkali, oil resistant boots. (×)
27, copper has good electrical and thermal conductivity, high mechanical strength, but it is easy to be oxidized when the test is high, the melting time is short, it is suitable for fast melt, protect the transistor. (×)
28, tin and lead metal materials with low melting point and long melting time, suitable for high-pressure fuse melt. (×)
29, the contact for strong electricity and the contact for weak current, the performance requirements are the same, the materials used are also the same. (×)
30. AlNiCo materials used as sensors, speakers and microwave devices are permanent magnet materials that provide a constant magnetic field in a given space. (√)
31. When the aluminum wires are connected, the winding method or the splicing method cannot be used like the copper wires, just because the aluminum wires have poor mechanical strength. (×)
32. The safe current carrying capacity of the wire should have different values ​​at different ambient temperatures. The higher the ambient temperature, the greater the safe current carrying capacity. (×)
33. When the steel core aluminum stranded wire passes through the alternating current, the current actually flows only from the aluminum wire due to the skin effect of the alternating current, so the effective sectional area is only the area of ​​the aluminum wire. (√)
34. The thermal resistance coefficient of the soil will affect the heat dissipation of the buried cable, thus affecting the safe current carrying capacity of the cable. The greater the thermal resistance coefficient, the greater the safe current carrying capacity of the cable. (×)
35. The cable tube (TC) and the tube wall are thin, and the nominal diameter refers to the inner diameter. (×)
36. The bare wire should be laid at a height of 3.5m or more, and it should not be erected below 3.5m. (×)
37. The wire is laid in the ceiling or ceiling, and can be protected without pipe. (×)
38. The cable is short and the traction is small. The traction head can be used to make the wire core with tension. When the traction force is large, it can be pulled by the steel wire sleeve. (×)
39. For all pipe-passing lines, there shall be no more than one pipe joint. (×)
40, cable cores sometimes press round, semi-circular, fan-shaped and other shapes, this is to reduce the cable dimensions and save raw materials. (√)#p#Page title#e#
41. The protective layer of the cable protects the cable core conductor. (×)
42. When the cable is moving, the cable reel should be placed flat on the car for fixing. (×)
43. In paper-insulated cables, the wrapped-type cable has a higher operating voltage than the split-phase lead-packed cable. (×)
44. Medium and low voltage PVC cables, polyethylene cables and cross-linked polyethylene cables, generally also have a completely sealed metal sheath, like paper insulated cables. (×)
45. When the cable is in operation, just monitor its load not to exceed the allowable value, and do not need to monitor the temperature of the cable, because both are consistent. (×)
46. ​​When the cable is sawn steel, the process is to tie the steel armor with a diameter of 2.0mm copper and tie it 3~4 ,. The winding direction of the copper wire should be opposite to that of the steel armor. (×)
47. When the substation is powered off, first isolate the switch and then cut off the circuit breaker. (×)
48. When the high-voltage isolating switch is in operation, if the surface of the insulator is severely discharged or the insulator is broken, the high-voltage isolating switch should be disconnected immediately and the operation should be terminated. (×)
49. The high-voltage load switch has an arc extinguishing device that can disconnect the short-circuit current. (×)
50. When replacing the quartz sand in the tube of the fuse, the quartz sand particles are the same size. (×)
51. The standby transformer should also be connected to the signal circuit in light gas relay. (√)
52. Unloaded voltage regulating transformer. After changing the tap switch, the DC resistance of each phase winding should be measured. The difference of DC resistance of each phase is not more than 10% of the minimum value of the three phases. (×)
53. Usually, the parallel capacitor bank is discharged by the voltage transformer or the discharge bulb after the circuit is cut off. Therefore, the substation can be repaired without manual discharge after power failure. (×)
54. After using the battery pack for a period of time, it is found that some battery voltages are already low, and most of the battery voltages are still high, so you can continue to use them. (×)
55. Electromagnetic overcurrent relay is instantaneous, and is often used for overcurrent protection or quick-break protection of lines and equipment. (√)
56. The operating time limit of the inductive overcurrent relay is proportional to the square of the current flowing. (×)
57. Gas (gas) protection can reflect various types of faults inside the transformer tank and also reflect some faults outside the tank. (×)
58. The primary current of the current transformer depends on the secondary current, the secondary current is large, and the primary current also becomes large. (×)
59. To replace the melt of the high-voltage fuse, copper or silver wire soldered with tin or shot ball, lead-tin alloy or silver wire, or melt made of lead-tin alloy or zinc. (×)
60. When the voltage transformer is in operation, its oil plug should be tightened. (×)
61. Vacuum circuit breakers are suitable for indoor and outdoor substations and industrial and mining enterprises of 35kV and below, where frequent operation is required and power distribution systems with many faults are particularly suitable for breaking capacitive load current. It has simple operation and maintenance and low noise. (√)
62. The shunt capacitor bank is allowed to operate at 1.1 times the rated voltage for a long time, allowing more than 30% of the rated current of the capacitor to operate for a long time. (√)
63. Inductive overcurrent relays combine the functions of electromagnetic current relays, time relays, signal relays and intermediate relays. It not only provides time-limited overcurrent protection, but also enables current quick-break protection. (√)
64. The general knife switch cannot cut off the fault current, nor can it withstand the electrodynamic and thermal effects caused by the fault current. (×)
65, low-voltage load switch (iron shell switch) can quickly open and close the knife switch, depending on the speed of the manual operating mechanism handle. (×)
66. When using a contactor (such as the CJ12 series) suitable for the long-term working system, it should be used for long-term work, and its capacity should be reduced to less than half of the rated capacity of the intermittent long-term working system. (√)
67. The contact resistance of the black oxide film formed by the breaking arc on the contactor silver and silver-based alloy contact surfaces is large and should be repaired. (×)
68. Motors that are frequently reversed and frequently switched on and off are suitable for thermal relay protection. (×)
69. Plastic shell type low voltage circuit breakers are widely used in switch cabinets for AC and DC distribution lines in industrial enterprises. Frame type low-voltage circuit breakers are often used to protect motors and lighting circuits with small capacity as control switches. (×)
70. In the flammable and explosive places, the lamps should be sealed or explosion-proof. In the dusty, humid and corrosive gas, the lamps should be waterproof and dustproof. (√)
71. For the lighting switch in dusty, humid places or outdoor places, the porcelain waterproof pull switch should be used. (√)
72. The rated capacity of the transformer is the apparent power of the transformer output. (√)
73. The power phase (fire) line can be directly connected to the luminaire, and the switch can control the ground. (×)
74. The safety voltage lighting transformer uses a double-turn transformer, and an autotransformer can also be used. (×)
75. The protective grounding end of the single-phase three-hole power socket (facing the uppermost end of the socket) and the zero-connecting end of the zero-connecting terminal can be connected by wires to share one wire. (×)
76, the power cord is connected to the socket or connected to the plug is the same. (×)
77. The phase (fire) line of the screw base should be connected to the tongue on the center of the lamp socket, and the neutral wire is connected to the threaded port. (√)
78. The rated voltage of the motor refers to the voltage of each phase input to the stator winding instead of the line voltage. (×)
79. The dynamic stability and thermal stability conditions at the start of the motor are reflected in the allowable starting conditions (direct or step-down) of the motor and the number of consecutive starts specified by the manufacturer. (√)#p#Page title#e#
80. When the asynchronous motor adopts Y-Δ step-down starting, the stator windings are first connected by Δ, and then changed to Y-connected operation. (×)
81. The short-term duration specified by the “short-time operation†of the motor does not exceed 10 minutes. (×)
82. The insulation class of the motor, indicating the insulation material of the motor winding and the level at which the wire can withstand the temperature limit. For example, Class E insulation allows a maximum temperature of 120 degrees Celsius. (√)
83. The method of decompression starting of autotransformer is suitable for frequent starting of cage asynchronous motor with capacity below 320kW. (×)
84. The starting method of the wound rotor asynchronous motor is usually started by Y-Δ decompression. (×)
85. Wound rotor asynchronous motor should use frequent varistor starting when running at heavy load and low speed. (×)
86. The characteristic of starting the motor with frequent varistor is that the resistance of the frequent varistor can increase smoothly with the increase of the motor speed. (×)
87. When the rotor of the wound rotor is started by the rotor string resistor, the larger the string resistance, the larger the starting torque. (×)
88. Check the insulation resistance between the stator and rotor winding phases of the low-voltage motor and the winding to ground. When measuring with 500V insulation resistance, the value should not be lower than 0.5M Ω, otherwise it should be dried. (√)
89. For the operation of only a single operation, accident handling operation, pulling the grounding knife and removing the only set of grounding wire, it is not necessary to fill in the operation ticket, but it should be recorded in the operation record book. (√)
90. The operation ticket must also be written to the lock, hang or disassemble the operation handle at the beginning. (×)
91. Operation of electrical equipment must be carried out by two people, with the lower level of personnel as the guardian and the higher level of operation. (×)
92. In the operation of the substation, the items such as connecting or disassembling the ground wire, inspecting electricity, and installing and disassembling the fuse of the voltage transformer circuit may not fill in the operation ticket. (×)
93. The power failure operation of the substation can not be filled in the operation ticket after the “inspection†work after the circuit is cut off. (×)
94. Rescuing the electrocution victims, using the excitable respiratory center of corramin, Lobeline, or the adrenaline and other cardiac acupuncture to replace the manual breathing and extrathoracic cardiac compression. (×)
95. The power supply is from the secondary power distribution station in the plant introduced by the total step-down transformer in the factory. If the transformer capacity is below 500kVA, no special person can be on duty, and only patrol inspection is arranged. (√)
96. After the electrical equipment is powered off, do not touch the equipment or enter the equipment's barrier before disconnecting the power switch and taking safety measures to avoid personal electric shock. (√)
97. Test the electrolytic capacitor with a multimeter R × 1 Ω file. The black meter is connected to the positive pole of the capacitor. The red test lead is connected to the negative pole. The needle is slowly increased. If it stops at 10k Ω, the capacitor is good. (×)
98. The forward voltage drop between the base and emitter of the manifold is greater than the forward voltage drop of the silicon tube. (×)
99. For the butt joint of the thick plate opening, the first layer of welding should use a thicker electrode. (×)
100. For the butt welding of horizontally fixed pipe fittings, it can be welded by one-way clockwise or counterclockwise welding. (×)
Second, multiple-choice questions (fill in the space of the correct answer number)
1. In the following meter accuracy level grouping, it can be used as the engineering measurement instrument as group c .
a , 0.1 , 0.2b , 0.5 , 1.0c , 1.5 , 2.5 , 5.0
2. To measure the average value of non-sinusoidal AC, a meter should be used.
a, rectification system b, electromagnetic series c, magnetoelectric series d, electric system
3, a magnetoelectric system DC meter, the meter full scale 100A, marked with the need for 100A, 75mV external shunt, today with a 300A, 75mV shunt, ammeter indicating 50A, the actual line current is c .
a, 50Ab, 100Ac, 150A
4. When using the clamp ammeter, you should use a larger range first, and then change the range according to the magnitude of the measured current. b should be switched when switching the range.
a, directly turn the range switch b, open the jaws first, then turn the range switch
5, to measure the insulation resistance of 380V AC motor, should use the insulation resistance meter with rated voltage b .
a, 250Vb, 500Vc, 1000V
6. When using the insulation resistance meter to measure the insulation resistance, connect the line L and the ground E end to the measured object with a single wire. The connection line at the a end should be well insulated from the earth.
a , Lb , E
7. For 10kV substation, the accuracy of the active energy meter is c grade, and the accuracy of the corresponding voltage and current transformer is b .
a, 0.2 b, 0.5 c, 1 d, 2
8, an inductive load, power is 800W, voltage 220V, power factor is 0.8, the optional power meter range can be b .
a, rated voltage 150V, current 10Ab, rated voltage 300V, current 5A#p#page title#e#
9. The current coil of the electric power meter should be connected in series to the circuit. The “generator end†with “*†should be connected to the b terminal in the circuit, and the other current terminal should be connected to a . The voltage coil is connected in parallel, and the “generator end†marked “*†is connected to d .
a, load side b, power supply side c, either side
d, either end of the current terminal button e, either end of the load
10, fast heating type soldering iron continuous power-on time can not exceed a .
a, 2minb, 5minc, 10min
11. Use high-voltage insulation rods for outdoor rainy days to block the flow of water and maintain a certain dry surface. Appropriate amount of rain cover should be added. The rain cover should be installed in the middle of the insulation rod. The rated voltage is 10kV or less, and the rain cover is not installed. Less than a , rated voltage 35kV is not less than c .
a, 2 b, 3 c, 4 d, 5 only
12, silver and its alloys and gold-based alloys are suitable for the production of c .
a, resistor b, potentiometer c, weak electrical contact d, strong electrical contact
13. The model of neoprene insulated wire is c .
a , BX , BLXb , BV , BLVc , BXF , BLXF
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