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136 Matching questions

  1. What purpose is served by a starting resistor in a motor circuit?
  2. What is the purpose of a frame ground in a trailing cable?
  3. The power of a transformer is rated by its:
  4. If an equipment frame grounding wire was not provided:
  5. A small sump pump blows a 20-amp fuse. The pump under full load draws 12 amps of current and receives its power through a No. 12 AWG cable. After repairing the problem, you discover you only have a 15-amp and a 30-amp fuse. You should:
  6. Three-pole single-throw disconnect switches have how many knife blades?
  7. If you wanted to find information concerning a motor's duty cycle characteristics, you could find it most easily by:
  8. Voltage is checked with an instrument called a (an):
  9. The purpose of a slip switch on a belt is to:
  10. Speed of DC motors can be controlled by:
  11. Series field leads of a DC motor are identified by:
  12. If the shunt field of a compound motor opens, the motor usually:
  13. If a transformer was believed to be shorted because of a breakdown in its insulation, what instrument would you use to check it?
  14. A diode blocks:
  15. How is the rotation of a direct current, series motor reversed?
  16. When a circuit breaker has an overload trip, what causes the circuit breaker to de-energize the circuit?
  17. The wires of a transformer have a 10:1 ratio. When stretched out side by side:
  18. The duty cycle of a motor refers to its characteristic:
  19. If the cross-sectional area (size) of a wire is decreased, its resistance will
  20. When dealing with electrical equipment, grounding:
  21. The unit of measurement of resistance to the flow of electricity is the:
  22. The DC motor that uses both a series and shunt winding and combines the characteristics of both is called a:
  23. A current that changes in magnitude but not in direction is called?
  24. If you checked a resistor marked 50 ohms and your meter read the resistance extremely high (your meter would not measure the amount), you would be most correct in assuming that:
  25. Of the devices listed below, what will change single-phase AC to DC?
  26. If a float switch on a pump closes because the water level rises:
  27. A rectifier does what:
  28. Heat sinks on a rectifier are provided to:
  29. If you read an open circuit between A1 and A2 of a DC motor, it indicates that:
  30. When a circuit breaker is tripped:
  31. If under normal load a 30-amp fuse becomes hot the most likely reason for this is:
  32. Pumps and section equipment are grounded by a:
  33. A blown fuse or a tripped circuit breaker could indicate all of the following EXCEPT:
  34. Two resistors (Resistor 1 and Resistor 2) are connected in parallel and Resistor 2 burns open. What would happen?
  35. A solenoid operates in the same way as a:
  36. When an overcurrent device detects an overload condition, the breaker should trip:
  37. A wire used for a temporary connection is termed a:
  38. A 3-phase motor continues to operate when one lead has been severed or cut in two; then, when stopped, will not start again. The motor is said to be:
  39. The heater element in a motor circuit overload relay is connected in:
  40. There are three types of electrical diagrams. Which of the following is NOT an electrical diagram?
  41. The direction in which a motor rotates depends upon the:
  42. If circuit breakers are too small for the equipment they are protecting:
  43. A transformer has primary windings of 460 volts and secondary windings of 115 volts. What can you correctly assume about wire size?
  44. If a 120-volt direct current source is connected to a 10:1 step-down transformer, the output on the secondary side is:
  45. The device that makes or breaks a circuit feeding a load is called a:
  46. Charging a 12-volt battery from a 12-volt AC source will:
  47. If you were to peel the insulation off a No. 14 AWG stranded conductor, you would expect to find:
  48. If a voltmeter were placed across the fuse and no voltage was indicated, you could correctly assume that:
  49. What is the same in all parts of a series circuit?
  50. What is the effect of dust and dirt between joints of permissible equipment?
  51. A shuttle car tramming up a steep grade at the feeder blows a fuse. Before knocking the power and tagging-out the circuit you must:
  52. What device may be installed in the neutral of a three-phase wye connected system to limit the current if a ground fault occurs?
  53. When comparing the resistance of the shunt field of a DC motor to the series field, the shunt field resistance is usually:
  54. If a voltmeter were placed across the fuse and the scale indicated 120 volts, you could correctly assume that:
  55. The idea behind a capacitor trip device and circuit is to:
  56. When compared to the resistance of the series fields and armature circuit, the shunt fields of a motor will have:
  57. Resistance is checked with an instrument called a(an):
  58. A hot stick shall be electrically tested:
  59. If the continuous miner stops operating, and the only component that is energized on the miner is its methane monitor, you could do all of the following EXCEPT:
  60. The part of a disconnect switch which has metal blades that pivot at one end is called a (an):
  61. The ampere capacity of a circuit breaker is:
  62. Five kilowatts equal how many watts?
  63. The main purpose of the overloads is to protect the:
  64. If you wanted to check the insulation on wire for damage, the instrument you would use is a (an):
  65. The safest way to check an electrical load to see if it is an open circuit is with a (an):
  66. In general, how should bandages be applied to a burn?
  67. When testing a diode with an ohmmeter, what will be the reading of a good diode?
  68. What is wrong with replacing a blown fuse with a piece of copper wire?
  69. The unit of measurement meaning "electrical pressure or force" is the:
  70. What is electrolysis?
  71. Using a shunt motor enables you to control:
  72. The function of the capacitor trip device and circuit is to:
  73. To reduce the hazard of electrical shock, which of the following should be installed?
  74. Thirty-five horsepower is equal to:
  75. With a shunt motor, speed is controlled by:
  76. Meggers are used to check:
  77. The motor overload relay contacts are connected in:
  78. If a circuit breaker with thermal overload protection has just tripped and you immediately try to re-energize the circuit and find that the breaker will not hold in, you should:
  79. What happens if the two line leads to a DC series motor are reversed?
  80. Thermal heater strips in circuit breakers or line starters are used to provide what protection?
  81. The current used for charging storage batteries is:
  82. The system using one ground wire and three hot wires, whose voltage is balanced 120 degrees apart is called:
  83. The thermal heater element of an overload relay is generally connected in:
  84. Transformers are used to:
  85. Which of the following is a true statement concerning the operational characteristics of an SCR?
  86. If a diode reads continuity in one direction and open in the other, it is probably:
  87. A solid state device most commonly used to control power output in a DC circuit is:
  88. A dual element fuse provides:
  89. Which of the following is not a characteristic of a series motor?
  90. The difference between a time delay and an instantaneous overcurrent relay:
  91. Arc chutes on contactors contain heavy copper coils that are called:
  92. What will happen to a DC shuttle car series wound motor if the chain or drive shaft would break?
  93. Fuses should be replaced with:
  94. The unit of measurement generally used when rating a capacitor is the:
  95. The main function of a thermal overload is to:
  96. If the cross-sectional area (size) of a wire is decreased, its resistance will:
  97. If 1,100 amps leave a rectifier on one conductor, how many amps will return to that rectifier on the other conductor?
  98. What purpose is served by a blowout coil used as a DC contactor?
  99. This stop switch is classified as:
  100. Which would require the largest wiring?
  101. A ground monitor circuit is used to:
  102. Magnetic trip units of a circuit breaker provide what protection?
  103. If you read a low resistance between leads S1 and S2 of a series motor, means that:
  104. Which of the following methods is NOT recommended for removing a victim from contact with electricity?
  105. Electrical pressure or electromotive force is defined as:
  106. A ground fault is a phase-to-ground short in the output of:
  107. The motor better suited to control hoisting is:
  108. A magnetic relay is either closed or opened by:
  109. A wire is marked "14 AWG". The number "14" refers to:
  110. The most commonly used short-circuit protective device for trailing cables is:
  111. A single element fuse provides:
  112. The material used to separate one electrical wire from another in a cable is called:
  113. If a thermal overload activates, causing a circuit to be de-energized, what must you do before the circuit can be re-energized?
  114. Through what piece of equipment is alternating current fed in order to lower its voltage?
  115. If an ohmmeter shows continuity across an SCR with no gate voltage applied, the SCR is probably:
  116. Which of the following is a good conductor of electricity?
  117. The safest way to de-energize a motor running on full load is:
  118. Thermal overloads are used for:
  119. If a belt conveyor loaded with coal was turned on, the starting torque would be greatest when the motor:
  120. If the motor developed an internal "direct short" between phases, the device to de-energize the circuit would be the:
  121. What is used to limit the starting current of a DC motor?
  122. Shunt fields of a DC motor are identified by:
  123. If you were to shunt-out a resistor, the resistor would:
  124. Current is checked with an instrument called a (an):
  125. When fuses are too big for the current requirement of the equipment being protected:
  126. To reverse the direction of a DC motor:
  127. If four cables all have the same insulation and circular mil value, which cable would be the most flexible?
  128. Which system requires only two power conductors and is generally used for control, lighting, and small loads?
  129. What is used to prevent the Forward and Reverse contactors in a motor reversing control from operating at the same time?
  130. Which will cause the power center circuit breaker for a continuous miner to trip faster?
  131. When checking resistance in an AC circuit when troubleshooting, what initial precaution must be taken?
  132. The component attached to the donut coil on one phase lead, between the contactors and motor, is normally used as a (an):
  133. The instantaneous setting of a circuit breaker is:
  134. If you were to lockout and tag the motor to begin repair work, the safest and most convenient place to do this would be at the:
  135. If neither indicating light were on, and the coil would not energize, what component is most likely defective?
  136. If a system designed for a 20-amp fuse blows, and an electrician replaces it with one rated at 30 amps:
  1. a Electrical and/or mechanical interlocks.
  2. b It will allow current flow in only one direction once it is gated.
  3. c Stop the drive when the belt is slipping.
  4. d Knife switch.
  5. e A circuit breaker.
  6. f An electrical system.
  7. g Proper fuses.
  8. h Provides a return path to the earth and prevents voltage from existing on the frames of the equipment.
  9. i Voltmeter.
  10. j Volt.
  11. k Single-phase power.
  12. l The shuttle car runs over the miner cable causing two conductors to come in contact with each other.
  13. m A megger.
  14. n Jumper.
  15. o Short circuit.
  16. p Direction of the current flow through the armature.
  17. q Overvoltage.
  18. r A low resistance reading in one direction and a very high reading in the other direction.
  19. s Too much current could be allowed to pass through, overheating. equipment and burning off insulation.
  20. t Block the machine so it doesn't move.
  21. u Current in the circuit would be reduced.
  22. v The resistor has burned open.
  23. w Pulsating current.
  24. x Momentary.
  25. y Looking at the tag attached to the motor housing
  26. z Wait for the thermal element in the breaker to cool sufficiently so that it will hold in the tripping mechanism.
  27. aa Silicon controlled rectifier.
  28. ab The copper wire will not provide adequate overcurrent protection.
  29. ac A variable resistance in a separate field circuit.
  30. ad Ammeter.
  31. ae Grounding resistor.
  32. af Carbon.
  33. ag F1 and F2 leads.
  34. ah There would be a real potential for electrical shock.
  35. ai The secondary windings would be larger in size (AWG) than those on the primary side.
  36. aj Once every calendar year.
  37. ak A 15-HP, 220-volt motor.
  38. al Series with the operating coil.
  39. am Loosely.
  40. an Not cause a voltage drop.
  41. ao Resistors.
  42. ap Jumper-out the methane monitor.
  43. aq Changes AC current to DC current.
  44. ar 1,100 amps.
  45. as The fuse was blown.
  46. at Three-phase.
  47. au Disconnect switch located near the motor.
  48. av Direction of rotation remains the same.
  49. aw To protect the operator from shock by keeping the equipment at earth potential.
  50. ax The pump should start because the float switch completed an electrical circuit
  51. ay Single phase.
  52. az A thermal element heats up and actuates the contacts.
  53. ba Not charge the battery
  54. bb Current remains the same at all loads.
  55. bc No current flows beyond it into the circuit.
  56. bd Voltage.
  57. be Microfarad.
  58. bf Frame ground conductor.
  59. bg The armature circuit is open.
  60. bh Relay.
  61. bi Allow it to cool.
  62. bj The fuse
  63. bk Megger.
  64. bl Insulation.
  65. bm Current.
  66. bn Power diagram.
  67. bo Circuit breaker.
  68. bp The clips holding the fuse are loose.
  69. bq Protect the motor from overload.
  70. br Series with the motor lead.
  71. bs Motor
  72. bt It helps to extinguish the arc when the contactor opens.
  73. bu Higher.
  74. bv Insure continuity of the grounding circuit.
  75. bw Ohm.
  76. bx 200 strands.
  77. by All three phases at the same time.
  78. bz Increase
  79. ca Blowout coils.
  80. cb Increase.
  81. cc 5,000 watts.
  82. cd The short circuit setting.
  83. ce Maximum time period it can safely operate.
  84. cf Provide sufficient energy to trip the breaker, even after the power goes off.
  85. cg An electromagnetic field.
  86. ch Knock the victim off with a nonconductive object.
  87. ci Zero volts.
  88. cj Speeds up.
  89. ck Joints cannot be closed tightly enough to get the required cooling action; therefore permissibility is destroyed.
  90. cl The action of an electrical current which carries away particles of a conductor.
  91. cm The fuse was good
  92. cn Current in one direction.
  93. co One wire would be ten times the length of the other.
  94. cp Overcurrent.
  95. cq A conductor connected to the system ground.
  96. cr By changing the direction of the current flow in either the armature or series field.
  97. cs Short circuit protection.
  98. ct S1and S2.
  99. cu Install the 15-amp fuse
  100. cv Lies primarily in how quickly they trip a circuit breaker.
  101. cw Insulation resistance.
  102. cx A fire may result or the equipment may become damaged.
  103. cy Provide sufficient energy to trip the breaker, even after power goes off.
  104. cz Smaller wires which are not insulated from one another.
  105. da Step up or step down AC voltage.
  106. db Compound motor.
  107. dc First starts
  108. dd 26.11KW.
  109. de Both speed and direction
  110. df The motor will overspeed to the point of destruction.
  111. dg Contactor.
  112. dh Three.
  113. di It limits the starting current during start-up by reducing the voltage.
  114. dj Ohmmeter
  115. dk The series field is good.
  116. dl The circuit breaker will not stay closed.
  117. dm Regulating the applied voltage.
  118. dn KVA rating.
  119. do Overload and single-phase protection on three-phase circuits.
  120. dp Ammeter
  121. dq Shorted.
  122. dr Cool the rectifier.
  123. ds A shunt motor.
  124. dt Rectifiers.
  125. du Reverse either the armature or the series field leads.
  126. dv Direct current.
  127. dw The amount of current that a breaker can carry under normal conditions.
  128. dx Disconnect the source voltage.
  129. dy Higher resistance.
  130. dz The size of the conductor.
  131. ea Good.
  132. eb Short circuit and overload protection.
  133. ec Transformers.
  134. ed Series with the motor circuit.
  135. ee Through the control circuit which will open the line contactors.
  136. ef Ohmmeter with power off.