The edge: Things you should know

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  1. individual conductors shall be insulated or covered. What is the exception? Considering a grounded conductor.
    The grounded conductor of a multi conductor cable shall be permitted to be bare. 230.22 exc.
  2. the difference between a neutral and a grounded circuit conductor is?
    A. only a neutral will have equal potential to the ungrounded conductors
    B. only a neutral outer covering his white or natural gray 
    C. only a neutral carries unbalanced current
    D. there is no difference
    • A. only a neutral will have equal potential to the ungrounded conductors
    • B. only a neutral outer covering his white or natural gray
    • C. only a neutral carries unbalanced current
    • D. there is no difference
    • in the NEC handbook under Article 200. 1 it states "the grounded conductor is often, but not always, the neutral conductor. As defined in Article 100, a neutral conductor is one that is connected to the neutral point of an electrical system. In a single phase, 2 wire or 3 phase, corner grounded Delta system, the intentionally grounded conductor is not a neutral conductor, because it is not connected to a system nuetral point. 
  3. power factor is ______ _________ of current and voltage in an AC circuit?
    phase displacement. Source: Journeyman Electrician exam questions and answers, Tom Henry 2011. Also it is the ratio of TP/AP (true power to apparent power and R/Z (Resistance to impedance.  The angle theta in a voltage or impedance triangle as well.
  4. hysteresis is? 
    A. the tool used to read the specific gravity of a battery  
    B the lagging of magnetism, in a magnetic metal, behind the magnetizing flux which produces it.
    C. The opposite of impedance
    D. none of these
    • A. the tool used to read the specific gravity of a battery  
    • B the lagging of magnetism, in a magnetic metal, behind the magnetizing flux which produces it.
    • C. The opposite of impedance 
    • D. none of these
  5. PVC shall have a minimum burial depth of?
    24 inches. source: table 300.5 nec
  6. is enamel painted conduit allowed to be used outdoors?
    • No.
    • Source: n.e.c 306.1
  7. the Wheatstone bridge method is used for accurate measurements of?
    • Resistance
    •  A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. Its operation is similar to the original potentiometer. It was invented bySamuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridge's initial uses was for the purpose of soils analysis and comparison.
  8. which of the following is true?
    A. EMT may be threaded
    B. the white colored conductor connected to the silver colored post on a duplex receptacle on a 120 volt two wire branch circuit is called the neutral conductor
    C. plastic water pipe is approved to be used for electrical conduit
    D. the screw shell of a lampholder may support a fixture Weighing 6 pounds.
    D. Per 314.27A1 exc. a vertically mounted luminaire or lampholder weighing not more than 6 pounds shall be permitted to be supported on other boxes or plaster rings that are secure to other boxes, provided that the lumineer or its supporting yoke, or the lamp holder, is secured to the box with no less than two number 6 or larger screws.
  9. when a circuit breaker is in the open position do you have a short in the grounded or the ungrounded conductor?
    either. However, if the question poses an ungrounded Delta system then it would not include the neutral and this is how Europe does things.  The Wye system is rarely common. Remember also a neutral carries unbalanced load and a grounded conductor does not. Tom Henry’s 2011 Journeyman Electrician exam questions and answers pp 21
  10. wire connectors are generally classified as what type? Thermal or pressure?
    both.
  11. voltage of a circuit is best defined as?
    the effective difference of potential between two conductors
  12. When calculating a motors wire size you find the FLC (full load current) wire size in the ampacity tables 310.15(B)2(6) in 2015, is this the wire size?
    No.  An adjustment factor of 125 percent must be applied for a continuous motor.
  13. What is the current drawn when PF is .91? This question requires what mathematical solution?
    • PF x voltage
    • I.E. watts         
    •       pf x voltage
  14. What must be remembered when using the lighting load demand factors, table 220.42 when calculating the total number of branch circuits for illumination?
    That table 220.42 “lighting load demand factors” shall not be used in determining the number of branch circuits.
  15. The amperage in a dual voltage motor will be ______ if the voltage is doubled despite ohm’s law finding I using R.

    Example question: A dual-voltage three-phase motor draws a current of 45 amperes when connected to a 240 volt, three phase circuit.  How much current will the same motor draw if connected to a 480 volt three-phase circuit? Source: Electrician’s exam preparation guide, Dale C. Brickner, 2011: PP 48
    halfed
  16. What formula is used to find ‘R’ (resistance) in a length of wire?
    • R=K×L
    •      CM  ;where CM is circular mils, K is specific resistance of 12.9 for copper and 21.2 for Aluminum, and L is length.
  17. Motor branch circuits and feeders ocpd is rounded up or down?
    • Motor branch circuits are rounded up and feeders are rounded down.  
  18. What is the Cubic inches of a #14 awg wire and a #12 wire?
    • #12 is 2.25 cu in.
    • #14 is 2.00 cu in.
  19. What is a motor branch circuit?
    Would the below image showing a conductor supplying multiple motors be a branch circuit?
    • That portion of the circuit that extends beyond the final over current protection. No.
  20. Noninsulated busbars will have a minimum space of_______ inches between the bottom of enclosure and busbars. What about insulated busbars?
    10 inches is the maximum space between enclosures and this. T408.5 And 8 inches if insulated.
  21. Although a wound rotor motor is used for speed control applications, what type of motor has a large speed range?
    A DC motor has this. Tom Henry 2011 Journeyman Exam Questions and Answers. PP4
  22. The normal rotation of an induction motor is? facing the front of the motor. (The front of motor is the end opposite the shaft).
    Counterclockwise is the normal rotation for this type of motor, not facing the shaft; whereas it is clockwise facing the shaft. Tom Henry 2011 Journeyman Exam Questions and Answers. PP19

    It's based on the direction of the rotating magnetic field, which is dependant on the phase rotation. Hence if you swap in two line leads on a three phase motor, the direction of the magnetic field and thus motor will reverse. (This would usually be T1 and T3)

    Reference https://www.physicsforums.com/threads/3-phase-induction-motor-direction-of-rotation.229734/
  23. What are the Chapters of the NEC?
    chapter 1, 2,3,4,5,6,7,8, & 9.
  24. What electrical apparatus concerns a Class A device?
    Ground-Fault Circuit Interrupter (GfCl)- A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a class A device.  NEC Definitions article 100.
  25. open circuit test on a transformer is a test for measuring what?  Define this.
    • iron losses are tested with this test on a transformer keeping the HV side open and using the LV side. iron loss: the loss of available energy by hysteresis and eddy currents in an electromagnetic apparatus (as a transformer) versus copper loss. Tom Henry 2011 Journeyman Exam Questions and Answers. PP30
    • Usually high voltage (HV) winding is kept open and the low voltage (LV) winding is connected to its normal supply. A wattmeter (W), ammeter (A) and voltmeter (V) are connected to the LV winding as shown in the figure. Now, applied voltage is slowly increased from zero to normal rated value of the LV side with the help of a variac. When the applied voltage reaches to the rated value of the LV winding, readings from all the three instruments are taken.
  26. hot resistance of an incandescent lamp is approximately______times its cold resistance.
    This type of resistance in an incandescent lamp is ten times the cold resistance. Tom Henry 2011 Journeyman Exam Questions and Answers. PP34
  27. What is the below image a picture of?
    Amphenol Plugs.  They must have the wires soldered on one end

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Author:
johnbowens
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304075
Filename:
The edge: Things you should know
Updated:
2017-05-12 17:54:04
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Nec Jatc Code Questions
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Description:
General nec nfpa 70 code trivia. Giving the electrician an upper edge. Focusing on little known exceptions or obscure code.
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