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Question 1. What is the unit of electrical resistance? A) Ampere B) Volt C) Ohm D) Watt Answer: C Explanation: The Ohm is the standard unit of electrical resistance, symbolized by Ω. Question 2. According to Ohm's Law, what is the formula to calculate current (I)? A) I = V × R B) I = V / R C) I = R / V D) I = P / V Answer: B Explanation: Ohm’s Law states that current equals voltage divided by resistance. Question 3. In a parallel circuit, the total resistance is: A) Greater than the largest resistor B) Equal to the sum of all resistors C) Less than the smallest resistor D) The same as a series circuit Answer: C Explanation: In parallel circuits, total resistance is always less than the smallest branch resistor. Question 4. Which device is used to step up or step down AC voltage? A) Capacitor B) Transformer C) Diode D) Fuse Answer: B Explanation: Transformers change AC voltages up or down through electromagnetic induction. Question 5. What does NEC stand for in the electrical field? A) National Electric Code B) National Emergency Code C) New Electric Cable D) National Engine Council Answer: A Explanation: NEC stands for National Electrical Code, which sets safety standards for electrical installation. Question 6. What is the standard frequency of AC power in the United States? A) 50 Hz B) 60 Hz C) 120 Hz D) 100 Hz Answer: B Explanation: The standard AC frequency in the U.S. is 60 hertz.
Question 7. Which of the following is the formula for calculating electrical power in watts? A) P = V × I B) P = V / I C) P = I / V D) P = R × V Answer: A Explanation: Power equals voltage times current (P = VI). Question 8. When calculating voltage drop, which factor is NOT relevant? A) Length of conductor B) Size of conductor C) Color of insulation D) Load current Answer: C Explanation: The color of the wire insulation does not affect voltage drop. Question 9. What is the minimum burial depth for UF cable in residential branch circuits per NEC? A) 6 inches B) 12 inches C) 18 inches D) 24 inches Answer: C Explanation: UF cable must be buried at least 18 inches deep per NEC 300.5. Question 10. The primary purpose of grounding electrical systems is to: A) Prevent corrosion B) Enhance circuit performance C) Provide a path for fault currents D) Lower voltage Answer: C Explanation: Grounding provides a safe path for fault currents to reduce shock hazards. Question 11. A branch circuit is defined as: A) The circuit between the service panel and the utility transformer B) The circuit between the final overcurrent device and the outlet(s) C) The main feeder to the building D) A looped circuit Answer: B Explanation: A branch circuit runs from the overcurrent device to the outlets or equipment. Question 12. What is the NEC minimum ampacity for service entrance conductors for a 200A residential service? A) 100A B) 150A C) 200A D) 225A Answer: C Explanation: Service entrance conductors must be rated at least for the service ampacity—in this case, 200A.
Question 19. Which wire color is typically used for the grounded (neutral) conductor in residential wiring? A) Black B) Green C) White D) Red Answer: C Explanation: White is the standard color for neutral (grounded) conductors. Question 20. For a 120V, 20A branch circuit, what is the minimum wire size permitted by the NEC for copper conductors? A) 18 AWG B) 14 AWG C) 12 AWG D) 10 AWG Answer: C Explanation: 12 AWG copper wire is the minimum for a 20A circuit per NEC 210.19. Question 21. What is the maximum allowable box fill for a standard 4-inch square box (21 cubic inches) using 12 AWG conductors? A) 5 B) 6 C) 8 D) 10 Answer: C Explanation: Each 12 AWG conductor counts as 2.25 cubic inches; 21/2.25 = 9.3, so up to 8 conductors plus allowances for devices and grounds. Question 22. Which of the following is NOT a type of raceway? A) EMT B) PVC C) MC D) NM Answer: D Explanation: NM (nonmetallic sheathed cable) is not a raceway, but a cable type. Question 23. The main difference between THHN and THWN wire insulation is: A) Color B) Voltage rating C) Wet location suitability D) Size Answer: C Explanation: THHN is for dry locations, THWN is rated for wet locations. Question 24. The minimum size pull box for straight pulls of 2-inch conduit per NEC is: A) 6 inches B) 8 inches C) 12 inches D) 16 inches
Answer: D Explanation: The pull box must be at least 8 times the conduit size (2” × 8 = 16”). Question 25. What is the continuous load definition per NEC? A) Load that operates for 1 hour B) Load that operates for 2 hours C) Load that operates for 3 hours or more D) Load that operates for 24 hours Answer: C Explanation: Continuous load is defined as a load that operates for three hours or more. Question 26. Which NEC article covers grounding and bonding? A) 200 B) 210 C) 250 D) 300 Answer: C Explanation: Article 250 of the NEC covers grounding and bonding. Question 27. What is required for a bathroom branch circuit in a dwelling? A) 10A B) Dedicated 20A circuit C) Shared 15A circuit D) 30A circuit Answer: B Explanation: Each bathroom must have a dedicated 20A branch circuit for receptacles. Question 28. When using flexible cords, which of the following is NOT permitted by the NEC? A) As a substitute for fixed wiring B) For portable lamps C) For pendants D) For appliances Answer: A Explanation: Flexible cords cannot be used as a substitute for permanent wiring. Question 29. What is the minimum working space depth in front of electrical panels (up to 600V) per NEC? A) 24 inches B) 30 inches C) 36 inches D) 48 inches Answer: C Explanation: NEC 110.26 requires a minimum of 36 inches clearance in front of panels. Question 30. Which of the following is used to limit the magnitude of current in a circuit? A) Capacitor B) Resistor C) Relay D) Transformer
D) Autotransformer Answer: C Explanation: Step-down transformers reduce standard voltage to low-voltage lighting systems. Question 37. Which of the following is the correct formula for calculating total resistance in a series circuit? A) 1/Rt = 1/R1 + 1/R2 + 1/R B) Rt = R1 + R2 + R C) Rt = R1 × R2 × R D) Rt = R1 – R2 + R Answer: B Explanation: In series, total resistance is the sum of all resistances. Question 38. What does "MC" stand for in electrical wiring? A) Metal Conduit B) Metal Clad C) Multi-Conductor D) Main Cable Answer: B Explanation: MC stands for Metal Clad cable. Question 39. What is the minimum number of 20A small appliance circuits required in a residence? A) 1 B) 2 C) 3 D) 4 Answer: B Explanation: At least two 20A small appliance branch circuits are required. Question 40. Which is NOT a permitted use of NM cable? A) In dry locations B) In damp locations C) In residential walls D) Above ceilings in dwellings Answer: B Explanation: NM cable is not listed for use in damp or wet locations. Question 41. The minimum size EGC (equipment grounding conductor) for a 30A circuit using copper wire is: A) 18 AWG B) 14 AWG C) 12 AWG D) 10 AWG Answer: B Explanation: NEC Table 250.122 specifies 10 AWG copper for 30A circuits. Question 42. Which NEC article covers wiring methods? A) 100 B) 200 C) 300
D) 400
Answer: C Explanation: NEC Article 300 covers wiring methods. Question 43. How often must exposed work in progress be inspected by a licensed Delaware electrical inspector? A) Daily B) Weekly C) Before concealment D) After completion only Answer: C Explanation: Inspections are required before work is concealed. Question 44. Which of the following is NOT considered a continuous load? A) Exit lighting B) Electric water heater C) Clothes dryer D) Emergency lighting Answer: C Explanation: Clothes dryers typically cycle and are not continuous loads. Question 45. Which conductor is required to be identified with a green or green with yellow stripes color? A) Hot B) Neutral C) Equipment grounding D) Control Answer: C Explanation: Equipment grounding conductors must be green or green/yellow. Question 46. The maximum number of #12 AWG conductors permitted in a 4-inch octagonal box ( cu in) is: A) 5 B) 6 C) 7 D) 9 Answer: B Explanation: Each #12 conductor is 2.25 cu in; 21/2.25 ≈ 9, but deductions for devices and grounds reduce the number to 6. Question 47. Which type of circuit breaker protects against both overcurrent and short circuits? A) AFCI B) GFCI C) Standard thermal-magnetic D) Isolation Answer: C Explanation: Standard circuit breakers protect against both overloads and short circuits. Question 48. What is the purpose of a bonding jumper? A) To increase voltage
B) 10
C) 12
D) 13
Answer: C Explanation: NEC allows up to 10 receptacles per 20A circuit, but 12 is commonly used based on 180 VA per outlet. Question 55. Which of the following is NOT a type of overcurrent protection device? A) Fuse B) Circuit breaker C) Ground rod D) Current-limiting breaker Answer: C Explanation: Ground rods are for grounding, not overcurrent protection. Question 56. When are arc-fault circuit interrupters (AFCIs) required in dwelling units? A) All lighting circuits B) All kitchen circuits C) Most 120V, 15 and 20A outlets in living areas D) Only in bedrooms Answer: C Explanation: AFCIs are required in most living areas for 120V, 15 and 20A circuits. Question 57. Which of the following is NOT required to be bonded to the service equipment? A) Gas piping B) Water piping C) Telephone system D) Metal building frame Answer: C Explanation: Communication systems are bonded separately, not to the main service. Question 58. What is the ampacity of #10 AWG copper wire with THHN insulation at 75°C? A) 20A B) 25A C) 30A D) 35A Answer: C Explanation: #10 AWG copper THHN is rated 30A at 75°C. Question 59. What is the minimum clearance above a residential driveway for service drop conductors? A) 8 ft B) 10 ft C) 12 ft D) 18 ft Answer: B Explanation: The minimum clearance is 12 feet for residential driveways. Question 60. What type of cable is commonly used for branch circuit wiring in residential buildings? A) MC
B) NM
C) AC
D) TC
Answer: B Explanation: NM (nonmetallic sheathed) cable is standard for residential wiring. Question 61. For a 20A, 120V circuit supplying receptacles in a dwelling, the maximum allowed voltage drop is: A) 1% B) 3% C) 5% D) 10% Answer: B Explanation: The recommended maximum voltage drop is 3%. Question 62. How are conductors in a raceway derated when more than three current-carrying conductors are present? A) No derating B) Ampacity increases C) Ampacity decreases D) Only neutral is derated Answer: C Explanation: Ampacity decreases due to heat buildup with more conductors. Question 63. What is the minimum burial depth for direct-buried cables under a driveway? A) 12 inches B) 18 inches C) 24 inches D) 30 inches Answer: C Explanation: Minimum depth is 24 inches under driveways. Question 64. Which of these appliances requires a dedicated branch circuit? A) Refrigerator B) Dishwasher C) Electric range D) Microwave oven Answer: C Explanation: Electric ranges require dedicated circuits due to high load. Question 65. Which of the following conductors is allowed to be used as a grounding electrode conductor? A) Aluminum B) Copper C) Steel D) All of the above Answer: D Explanation: All may be used, but aluminum can't be used in earth contact or where subject to corrosion.
A) 1/0 AWG
B) 2 AWG
C) 2/0 AWG
D) 4 AWG
Answer: B Explanation: For 100A, minimum aluminum size is 2 AWG. Question 73. If three 100W light bulbs are wired in parallel to a 120V source, what is the total current drawn? A) 0.83A B) 1.67A C) 2.5A D) 3.5A Answer: C Explanation: Each draws 0.83A; 0.83 × 3 = 2.5A. Question 74. Which of the following is NOT a function of a transformer? A) Changing voltage levels B) Providing electrical isolation C) Changing AC to DC D) Matching impedance Answer: C Explanation: Transformers don't convert AC to DC. Question 75. Which of the following must be connected to the equipment grounding conductor? A) Metal boxes B) Plastic boxes C) Wood panels D) Drywall Answer: A Explanation: Metal boxes must be grounded. Question 76. What is the minimum rating for a general use receptacle in a dwelling unit? A) 10A B) 15A C) 20A D) 25A Answer: B Explanation: The minimum is 15 amps. Question 77. Which of the following devices is used to protect against electrical fires caused by arcing? A) GFCI B) Standard breaker C) AFCI D) Isolation transformer Answer: C Explanation: AFCIs detect and interrupt arc faults.
Question 78. What is the minimum size copper wire required for a 60A feeder? A) 6 AWG B) 4 AWG C) 2 AWG D) 1 AWG Answer: A Explanation: 6 AWG copper is required for 60A. Question 79. How far must a receptacle be from a bathroom sink? A) 1 ft B) 2 ft C) 3 ft D) 6 ft Answer: C Explanation: Receptacles are permitted within 3 feet of a bathroom sink. Question 80. The maximum number of conductors allowed in a single conduit is determined by: A) Voltage B) Conduit size and wire size C) Current D) Color Answer: B Explanation: Conduit fill tables in NEC determine this based on size. Question 81. Which is the correct color code for a 277V circuit conductor? A) Black B) Red C) Brown D) Blue Answer: C Explanation: Brown is standard for 277V phase conductors. Question 82. Equipment grounding conductors are required to be: A) Insulated only B) Bare or insulated C) Only bare D) Only green Answer: B Explanation: They may be bare or insulated. Question 83. What is the required ampacity for a feeder supplying a continuous load of 40A? A) 40A B) 44A C) 50A D) 55A Answer: C Explanation: Feeder must be rated at least 125% of continuous load (40 × 1.25 = 50A). Question 84. When must a disconnecting means be located within sight of a motor? A) Always
C) 277V
D) 208V
Answer: A Explanation: Each hot to neutral is 120V in a split-phase system. Question 91. Which of the following is used to calculate short-circuit current available at a panel? A) Ohm’s Law B) Power factor C) Fault current calculation D) Voltage drop Answer: C Explanation: Fault current calculation methods are used. Question 92. The maximum number of 12 AWG conductors allowed in a 3/4-inch EMT is: A) 6 B) 9 C) 12 D) 16 Answer: C Explanation: According to NEC tables, 12 conductors of 12 AWG are allowed. Question 93. Which of the following is NOT a requirement for service equipment? A) Readily accessible B) Marked with voltage and current rating C) Located outdoors only D) Capable of being locked in open position Answer: C Explanation: Service equipment can be inside or outside but must be accessible. Question 94. What is the minimum size copper grounding electrode conductor for a 200A service? A) 6 AWG B) 4 AWG C) 2 AWG D) 1/0 AWG Answer: B Explanation: 4 AWG copper is required for up to 200A. Question 95. Which NEC article covers branch circuits? A) 200 B) 210 C) 215 D) 220 Answer: B Explanation: Article 210 covers branch circuits. Question 96. What is the minimum size THHN copper conductor for a 20A circuit? A) 18 AWG B) 14 AWG C) 12 AWG D) 10 AWG
Answer: C Explanation: 12 AWG is required for 20A. Question 97. What is the purpose of bonding a gas pipe to the electrical system? A) Ensure gas flow B) Prevent corrosion C) Prevent arcing and potential shock D) Increase gas pressure Answer: C Explanation: Bonding prevents dangerous voltage differences. Question 98. How much free conductor length must be left at each outlet box for splicing? A) 2 inches B) 4 inches C) 6 inches D) 8 inches Answer: C Explanation: NEC requires at least 6 inches of free conductor. Question 99. Which of the following is NOT a permitted use of flexible cords? A) For portable appliances B) As a substitute for permanent wiring C) For pendants D) For portable lamps Answer: B Explanation: Flexible cords can't replace permanent wiring. Question 100. What is the minimum wire size for a 100A feeder using copper conductors (THHN)? A) 8 AWG B) 6 AWG C) 4 AWG D) 2 AWG Answer: D Explanation: 2 AWG copper is required. Question 101. Which of the following is required for all receptacles in a laundry area? A) AFCI protection B) GFCI protection C) 10A circuit D) 30A circuit Answer: B Explanation: Laundry area receptacles must be GFCI protected. Question 102. What is the NEC maximum allowable number of bends between pull points in a conduit run? A) 90° B) 180° C) 270° D) 360°
Question 109. What is the maximum load permitted on a 20A branch circuit with continuous load? A) 16A B) 18A C) 20A D) 24A Answer: A Explanation: Continuous load cannot exceed 80% of breaker rating (16A on 20A). Question 110. What is the minimum number of receptacle outlets required in a 12-foot long wall in a living room? A) 1 B) 2 C) 3 D) 4 Answer: B Explanation: At least one outlet for every 12 feet of wall. Question 111. Which NEC article covers motors? A) 230 B) 240 C) 430 D) 440 Answer: C Explanation: Article 430 covers motors. Question 112. What is the minimum clearance for overhead service conductors above public streets? A) 12 ft B) 15 ft C) 18 ft D) 20 ft Answer: C Explanation: The minimum clearance is 18 feet. Question 113. When is a ground-fault circuit interrupter (GFCI) required outdoors? A) Only in wet locations B) For all outdoor receptacles C) Only for lighting D) Never Answer: B Explanation: All outdoor 125V, 15 and 20A receptacles must be GFCI protected. Question 114. What is the minimum wire size for a 15A branch circuit (copper)? A) 18 AWG B) 16 AWG C) 14 AWG D) 12 AWG Answer: C Explanation: 14 AWG is the minimum for 15A circuits.
Question 115. Which of the following is NOT a function of a panelboard? A) Distribute power B) Provide overcurrent protection C) Provide a ground connection D) Step up voltage Answer: D Explanation: Panelboards do not change voltage. Question 116. What is the minimum distance between the edge of a wood stud and a bored hole for NM cable? A) 1/2 inch B) 3/4 inch C) 1 inch D) 2 inches Answer: A Explanation: NEC requires a minimum of 1-1/4 inch from the edge, but if less, protection must be provided. Question 117. What is the ampacity of a 12 AWG copper conductor with THHN insulation at 60°C? A) 15A B) 20A C) 25A D) 30A Answer: B Explanation: 12 AWG copper is rated 20A. Question 118. Which of the following is NOT a characteristic of a parallel circuit? A) Same current in all branches B) Same voltage across all branches C) Multiple paths for current D) Total current is sum of branch currents Answer: A Explanation: Each branch can have different current. Question 119. What is the maximum continuous load on a 100A panel? A) 60A B) 80A C) 100A D) 125A Answer: B Explanation: Maximum continuous load is 80% of panel rating. Question 120. When sizing a pull box for angle pulls, what is the NEC minimum distance from the raceway entry to the opposite wall? A) 4 times conduit size B) 6 times conduit size C) 8 times conduit size D) 10 times conduit size Answer: B Explanation: For angle pulls, box size must be at least 6 times the largest conduit.
