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Stuff Every Electrician Should Know

Journeyman electrician exam prep: theory, safety and National Electrical Code concepts.

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  1. One ohm of resistance is defined as one volt for every what?
    Show the answer

    Ampere. Resistance is how much voltage it takes to push a given current. If 1 volt pushes 1 amp through a conductor, that conductor has 1 ohm.

  2. In Ohm's law, current through a resistor is directly proportional to what?
    Show the answer

    The voltage applied across it. Double the voltage across the same resistor and the current doubles. Resistance sits on the other side of the equation, so more resistance means less current.

  3. In a series circuit, which quantity is the same through every resistor?
    Show the answer

    Current. There is only one path, so every charge that goes through the first resistor must go through the next. The voltage splits up, but the current does not.

All 100 practice questions

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  1. One ohm of resistance is defined as one volt for every what?
  2. In Ohm's law, current through a resistor is directly proportional to what?
  3. In a series circuit, which quantity is the same through every resistor?
  4. In a parallel circuit, which quantity is the same across every branch?
  5. Two 10 ohm resistors are wired in parallel. What is the total resistance?
  6. Kirchhoff's junction rule says the current entering a junction does what?
  7. Counting the source too, the voltage changes around any closed loop in a circuit add up to what?
  8. To measure the voltage across a device, how is a voltmeter connected?
  9. To measure current with an in-line ammeter, how is it connected to the circuit?
  10. Compared with the circuit it measures, a good voltmeter has what kind of resistance?
  11. A 120 volt AC outlet reaches a peak of about what voltage?
  12. Why do utilities send electricity over long distances at very high voltage?
  13. Electric power in watts equals current in amps multiplied by what?
  14. In an AC circuit with only a resistor, how do voltage and current line up?
  15. In an AC circuit, the current through a capacitor does what compared with its voltage?
  16. Power factor compares the real power in watts with what?
  17. AC voltages and currents are usually quoted as which kind of value?
  18. In a three-phase system, how far apart in time are the three voltages, in degrees?
  19. In a wye system, line-to-line voltage is how many times line-to-neutral voltage?
  20. In a balanced three-phase wye system, how much current flows in the neutral?
  21. OSHA's lockout/tagout standard exists to prevent what?
  22. Under OSHA rules, who normally removes a lockout or tagout device?
  23. At a minimum, how often must a lockout/tagout procedure be inspected?
  24. Why is a lock considered stronger than a tag in lockout/tagout?
  25. OSHA says the path to ground from circuits and equipment must be permanent, continuous and what?
  26. On a construction site, what may OSHA accept instead of GFCIs to protect workers?
  27. OSHA says live parts must be what before an employee works on or near them?
  28. Portable ladders used near energized parts must have what kind of side rails?
  29. Rubber insulating gloves must be electrically tested before first issue and how often afterward?
  30. Along with a visual check, what must insulating gloves get before each day's use?
  31. Leather protector gloves go where relative to rubber insulating gloves?
  32. An arc flash can reach temperatures of up to about how many degrees Fahrenheit?
  33. The arc flash boundary is the distance at which incident energy equals what?
  34. Voltage-rated gloves are required inside the restricted approach boundary of exposed conductors at what voltage or higher?
  35. You see an open disconnect switch. Does that prove the circuit beyond it is dead?
  36. GFCIs address shock hazards. What do AFCIs address?
  37. At a minimum, how often should you test a GFCI?
  38. At roughly what current level can muscles lock up so you can't let go?
  39. University safety guidance says current as low as about how much can cause injury?
  40. When measuring current with a clamp meter, how many conductors should be inside the jaws?
  41. Fluke says to check a voltage detector on what before and after each use?
  42. Before measuring resistance with a multimeter, what must you do to the circuit?
  43. When measuring AC voltage with a digital multimeter, the black lead goes in which jack?
  44. What happens if you measure voltage with the leads plugged into the A or mA inputs?
  45. Fluke lists feeders and branch circuits fed from distribution panels in which meter category?
  46. Your meter's test probe has cracked insulation. What should you do?
  47. Under OSHA 1910.333, who may work on electric parts that have not been deenergized?
  48. A GFCI protects people by tripping when current leaks at about what level?
  49. In 2003, CPSC engineers estimated AFCIs could address about what share of home wiring fires?
  50. OSHA's 1910.304 requires GFCI protection for receptacles in bathrooms and where else?
  51. Under the 2023 NEC, which dwelling unit kitchen receptacles need GFCI protection?
  52. The 2026 NEC bans kitchen receptacle outlets within how far below the countertop surface?
  53. In the 2023 NEC, what is true about receptacles for kitchen islands and peninsulas?
  54. Which appliance did the 2023 NEC newly require GFCI protection for (150V or less to ground, 60A or less)?
  55. In the 2026 NEC, GFCI protection applies to outdoor outlets rated up to how many amps?
  56. Under the 2026 NEC, where must the service disconnect of a one- or two-family dwelling be?
  57. The 2026 NEC removed which threshold from the arc flash marking rule in 110.16?
  58. The 2026 NEC 408.6 requires what to be field marked on panelboards outside one- and two-family dwellings?
  59. In NEC terms, grounding means connecting a system or equipment to what?
  60. In the NEC, bonding means doing what to metal parts?
  61. To trip a breaker during a fault, current must have a low-impedance path back to where?
  62. A ground rod by itself does what for metal parts that are not bonded?
  63. A ground rod electrode must be at least how long in contact with the earth?
  64. Under 240.4(D), the maximum overcurrent device for 14 AWG copper is how many amps?
  65. For conductors 18 AWG to 10 AWG, what two things limit the size of the overcurrent device?
  66. The 240.4(B) 'next size up' rule allows rounding up the overcurrent device only up to what rating?
  67. In a box fill calculation, each 14 AWG conductor counts as how many cubic inches?
  68. In box fill, a single-gang device yoke (a switch or receptacle) counts as how many conductor volumes?
  69. In box fill, how do all of the equipment grounding conductors in a box count?
  70. Pool equipotential bonding conductors can be solid copper no smaller than what size?
  71. In the 2023 NEC, the pool perimeter surface for bonding extends how far horizontally from the inside wall?
  72. For an unpaved pool perimeter, the copper bonding conductor is located how far from the inside pool wall?
  73. Where no other bonded part touches the pool water, a conductive surface must expose how much area to the water?
  74. In the NEC rapid shutdown rules, the array boundary is how far from the PV array in all directions?
  75. In the 2023 NEC, one rapid shutdown option limits conductors inside the array boundary to how many volts within 30 seconds?
  76. NM cable must be secured within how far of an outlet box or fitting?
  77. After the first support at the box, NM cable must be supported at intervals not exceeding what?
  78. Branch-circuit conductors serving a single motor must have an ampacity of at least what percent of the motor's FLC?
  79. A motor with a 1.15 or higher service factor can have overload protection sized to what maximum percent of nameplate current?
  80. A motor disconnect must have an ampere rating of at least what percent of the motor's full load current?
  81. A service can have up to how many service disconnects?
  82. Outside of one- and two-family dwellings, a service disconnect installed indoors must be where?
  83. In the NEC, equipment is 'in sight from' other equipment if visible and not more than how far away?
  84. The Article 100 definition says an AFCI protects by recognizing what?
  85. A standard circuit breaker trips on overloads and what other condition, but not on arcing?
  86. Which NEC edition added kitchens and laundry rooms to the AFCI requirement?
  87. Under the 2023 NEC, AFCI protection in 210.12 applies to which dwelling unit branch circuits?
  88. The width of the working space in front of electrical equipment must be at least how wide?
  89. The working space in front of a panelboard must be clear to a height of at least what?
  90. Flexible metal conduit (Article 348) is mainly used for what?
  91. NEC Article 358 covers which raceway?
  92. Which raceway is described as inexpensive and easy to install, but brittle in the cold and prone to sag in heat?
  93. Which conductor insulation type is typically used in dry and damp locations but not wet locations?
  94. Tamper-resistant receptacles are not required when the receptacle is located more than how high above the floor?
  95. Which colors identify an insulated grounded (neutral) conductor under Section 200.6?
  96. A Class A GFCI trips when ground-fault current is at least how many milliamperes?
  97. How many 20-ampere small-appliance branch circuits must a dwelling kitchen have at minimum?
  98. In dwelling unit rooms, receptacles along walls can be spaced no more than how far apart?
  99. A bathroom receptacle must be within how far of the outside edge of each basin?
  100. In a box fill calculation, each 12 AWG conductor counts as how many cubic inches?