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140 True/False questions

  1. If four cables all have the same insulation and circular mil value, which cable would be the most flexible?200 strands.


  2. When dealing with electrical equipment, grounding:Provides a return path to the earth and prevents voltage from existing on the frames of the equipment.


  3. A hot stick shall be electrically tested:The action of an electrical current which carries away particles of a conductor.


  4. A solid state device most commonly used to control power output in a DC circuit is:Silicon controlled rectifier.


  5. The unit of measurement generally used when rating a capacitor is the:Volt.


  6. What is the same across each part of a parallel circuit?The amount of current that a breaker can carry under normal conditions.


  7. When fuses are too big for the current requirement of the equipment being protected:Too much current could be allowed to pass through, overheating. equipment and burning off insulation.


  8. Five kilowatts equal how many watts?Overload and single-phase protection on three-phase circuits.


  9. The device that makes or breaks a circuit feeding a load is called a:Contactor.


  10. A wire used for a temporary connection is termed a:Jumper.


  11. When comparing the resistance of the shunt field of a DC motor to the series field, the shunt field resistance is usually:Ohm.


  12. A single element fuse provides:Current in one direction.


  13. Electrical pressure or electromotive force is defined as:Voltage.


  14. The safest way to check an electrical load to see if it is an open circuit is with a (an):Ohmmeter with power off.


  15. What will happen to a DC shuttle car series wound motor if the chain or drive shaft would break?The motor will overspeed to the point of destruction.


  16. Three-pole single-throw disconnect switches have how many knife blades?Three.


  17. The main function of a thermal overload is to:Motor


  18. Arc chutes on contactors contain heavy copper coils that are called:Blowout coils.


  19. If you were to shunt-out a resistor, the resistor would:Not cause a voltage drop.


  20. 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:Protect the motor from overload.


  21. What is electrolysis?The action of an electrical current which carries away particles of a conductor.


  22. If a voltmeter were placed across the fuse and no voltage was indicated, you could correctly assume that:The fuse was good


  23. The motor overload relay contacts are connected in:KVA rating.


  24. Resistance is checked with an instrument called a(an):Ohmmeter


  25. If a thermal overload activates, causing a circuit to be de-energized, what must you do before the circuit can be re-energized?Allow it to cool.


  26. If the shunt field of a compound motor opens, the motor usually:Speeds up.


  27. Heat sinks on a rectifier are provided to:Short circuit protection.


  28. The most commonly used short-circuit protective device for trailing cables is:A circuit breaker.


  29. Which system requires only two power conductors and is generally used for control, lighting, and small loads?Current remains the same at all loads.


  30. When an overcurrent device detects an overload condition, the breaker should trip:All three phases at the same time.


  31. Which of the following is a true statement concerning the operational characteristics of an SCR?It will allow current flow in only one direction once it is gated.


  32. A diode blocks:Changes AC current to DC current.


  33. When testing a diode with an ohmmeter, what will be the reading of a good diode?Rectifiers.


  34. If you read an open circuit between A1 and A2 of a DC motor, it indicates that:Reverse either the armature or the series field leads.


  35. Current is checked with an instrument called a (an):Momentary.


  36. To reduce the hazard of electrical shock, which of the following should be installed?Voltage.


  37. Which of the following methods is NOT recommended for removing a victim from contact with electricity?Knock the victim off with a nonconductive object.


  38. If you were to peel the insulation off a No. 14 AWG stranded conductor, you would expect to find:Smaller wires which are not insulated from one another.


  39. What is used to prevent the Forward and Reverse contactors in a motor reversing control from operating at the same time?Electrical and/or mechanical interlocks.


  40. Which of the following is a good conductor of electricity?A variable resistance in a separate field circuit.


  41. This stop switch is classified as:Proper fuses.


  42. The component attached to the donut coil on one phase lead, between the contactors and motor, is normally used as a (an):Ammeter


  43. What is used to limit the starting current of a DC motor?Resistors.


  44. Speed of DC motors can be controlled by:Regulating the applied voltage.


  45. To reverse the direction of a DC motor:Reverse either the armature or the series field leads.


  46. Through what piece of equipment is alternating current fed in order to lower its voltage?Transformers.


  47. The main purpose of the overloads is to protect the:Motor


  48. A blown fuse or a tripped circuit breaker could indicate all of the following EXCEPT:Overvoltage.


  49. Voltage is checked with an instrument called a (an):Current.


  50. The overload relay contacts of a thermal overload are generally connected in:S1and S2.


  51. The current used for charging storage batteries is:Stop the drive when the belt is slipping.


  52. Electron flow in a conductor is defined as:Current.


  53. The material used to separate one electrical wire from another in a cable is called:Insulation.


  54. Charging a 12-volt battery from a 12-volt AC source will:The amount of current that a breaker can carry under normal conditions.


  55. There are three types of electrical diagrams. Which of the following is NOT an electrical diagram?Power diagram.


  56. 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:Install the 15-amp fuse


  57. Magnetic trip units of a circuit breaker provide what protection?An electromagnetic field.


  58. When a circuit breaker has an overload trip, what causes the circuit breaker to de-energize the circuit?A thermal element heats up and actuates the contacts.


  59. The safest way to de-energize a motor running on full load is:A shunt motor.


  60. Thirty-five horsepower is equal to:26.11KW.


  61. With a shunt motor, speed is controlled by:A variable resistance in a separate field circuit.


  62. Fuses should be replaced with:Current in one direction.


  63. 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:Block the machine so it doesn't move.


  64. If an ohmmeter shows continuity across an SCR with no gate voltage applied, the SCR is probably:The fuse was blown.


  65. What is the purpose of a frame ground in a trailing cable?Stop the drive when the belt is slipping.


  66. Shunt fields of a DC motor are identified by:F1 and F2 leads.


  67. The system using one ground wire and three hot wires, whose voltage is balanced 120 degrees apart is called:Three-phase.


  68. How is the rotation of a direct current, series motor reversed?Current.


  69. The thermal heater element of an overload relay is generally connected in:Series with the operating coil.


  70. A magnetic relay is either closed or opened by:An electromagnetic field.


  71. The difference between a time delay and an instantaneous overcurrent relay:Lies primarily in how quickly they trip a circuit breaker.


  72. If circuit breakers are too small for the equipment they are protecting:The circuit breaker will not stay closed.


  73. What is the effect of dust and dirt between joints of permissible equipment?Joints cannot be closed tightly enough to get the required cooling action; therefore permissibility is destroyed.


  74. In general, how should bandages be applied to a burn?Loosely.


  75. When checking resistance in an AC circuit when troubleshooting, what initial precaution must be taken?Higher.


  76. If the cross-sectional area (size) of a wire is decreased, its resistance will:Increase


  77. What device may be installed in the neutral of a three-phase wye connected system to limit the current if a ground fault occurs?Higher.


  78. The direction in which a motor rotates depends upon the:Direction of the current flow through the armature.


  79. The unit of measurement of resistance to the flow of electricity is the:Volt.


  80. What happens if the two line leads to a DC series motor are reversed?Direction of rotation remains the same.


  81. Which of the following is not a characteristic of a series motor?Resistors.


  82. If you wanted to check the insulation on wire for damage, the instrument you would use is a (an):Megger.


  83. Thermal heater strips in circuit breakers or line starters are used to provide what protection?Overcurrent.


  84. The heater element in a motor circuit overload relay is connected in:Maximum time period it can safely operate.


  85. When a circuit breaker is tripped:No current flows beyond it into the circuit.


  86. A transformer has primary windings of 460 volts and secondary windings of 115 volts. What can you correctly assume about wire size?A megger.


  87. The ampere capacity of a circuit breaker is:No current flows beyond it into the circuit.


  88. Meggers are used to check:Insulation resistance.


  89. The function of the capacitor trip device and circuit is to:Stop the drive when the belt is slipping.


  90. A ground monitor circuit is used to:Overload and single-phase protection on three-phase circuits.


  91. 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:Increase


  92. The unit of measurement meaning "electrical pressure or force" is the:Volt.


  93. The duty cycle of a motor refers to its characteristic:Maximum time period it can safely operate.


  94. Two resistors (Resistor 1 and Resistor 2) are connected in parallel and Resistor 2 burns open. What would happen?Voltage.


  95. Thermal overloads are used for:Overload and single-phase protection on three-phase circuits.


  96. A ground fault is a phase-to-ground short in the output of:An electrical system.


  97. Which will cause the power center circuit breaker for a continuous miner to trip faster?Series with the motor circuit.


  98. The wires of a transformer have a 10:1 ratio. When stretched out side by side:KVA rating.


  99. A wire is marked "14 AWG". The number "14" refers to:Protect the motor from overload.


  100. If neither indicating light were on, and the coil would not energize, what component is most likely defective?Protect the motor from overload.


  101. Pumps and section equipment are grounded by a:A conductor connected to the system ground.


  102. What purpose is served by a starting resistor in a motor circuit?It helps to extinguish the arc when the contactor opens.


  103. A current that changes in magnitude but not in direction is called?Jumper.


  104. What is the same in all parts of a series circuit?Voltage.


  105. The idea behind a capacitor trip device and circuit is to:Provide sufficient energy to trip the breaker, even after the power goes off.


  106. When compared to the resistance of the series fields and armature circuit, the shunt fields of a motor will have:Motor


  107. The DC motor that uses both a series and shunt winding and combines the characteristics of both is called a:Compound motor.


  108. 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:No current flows beyond it into the circuit.


  109. If the motor developed an internal "direct short" between phases, the device to de-energize the circuit would be the:Circuit breaker.


  110. Series field leads of a DC motor are identified by:S1and S2.


  111. If under normal load a 30-amp fuse becomes hot the most likely reason for this is:The pump should start because the float switch completed an electrical circuit


  112. If an equipment frame grounding wire was not provided:Short circuit and overload protection.


  113. Of the devices listed below, what will change single-phase AC to DC?Rectifiers.


  114. If 1,100 amps leave a rectifier on one conductor, how many amps will return to that rectifier on the other conductor?1,100 amps.


  115. If you wanted to find information concerning a motor's duty cycle characteristics, you could find it most easily by:Maximum time period it can safely operate.


  116. If a voltmeter were placed across the fuse and the scale indicated 120 volts, you could correctly assume that:The fuse was good


  117. What purpose is served by a blowout coil used as a DC contactor?It helps to extinguish the arc when the contactor opens.


  118. The power of a transformer is rated by its:26.11KW.


  119. If the cross-sectional area (size) of a wire is decreased, its resistance willIncrease


  120. A rectifier does what:Insulation resistance.


  121. A solenoid operates in the same way as a:Short circuit protection.


  122. If a float switch on a pump closes because the water level rises:Cool the rectifier.


  123. The motor better suited to control hoisting is:Momentary.


  124. The purpose of a slip switch on a belt is to:Stop the drive when the belt is slipping.


  125. A dual element fuse provides:Insulation resistance.


  126. If a belt conveyor loaded with coal was turned on, the starting torque would be greatest when the motor:Resistors.


  127. 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:Smaller wires which are not insulated from one another.


  128. If a 120-volt direct current source is connected to a 10:1 step-down transformer, the output on the secondary side is:Zero volts.


  129. Which would require the largest wiring?A 15-HP, 220-volt motor.


  130. If the overcurrent condition continues for a long time, and at a great enough magnitude, an overcurrent device will trip the:Circuit breaker.


  131. The instantaneous setting of a circuit breaker is:The short circuit setting.


  132. 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:Single phase.


  133. If a diode reads continuity in one direction and open in the other, it is probably:Good.


  134. Transformers are used to:Current in one direction.


  135. Using a shunt motor enables you to control:A variable resistance in a separate field circuit.


  136. If a transformer was believed to be shorted because of a breakdown in its insulation, what instrument would you use to check it?A megger.


  137. If you read a low resistance between leads S1 and S2 of a series motor, means that:Not cause a voltage drop.


  138. If a system designed for a 20-amp fuse blows, and an electrician replaces it with one rated at 30 amps:A fire may result or the equipment may become damaged.


  139. What is wrong with replacing a blown fuse with a piece of copper wire?The copper wire will not provide adequate overcurrent protection.


  140. The part of a disconnect switch which has metal blades that pivot at one end is called a (an):Knife switch.