THE 9TH FLOOR
Compliance Made Simple
C-10 Electrical Contractor
Practice Exam 1 - 50 Questions
Questions
50
Passing Score
72%
Time Limit
4 Hours
Format
Open Book
QUESTION 1 OF 50
What is the standard voltage for a single-phase residential service in the United States?
✓ Correct Answer: C) 120/240 volts
Standard residential service in the US is 120/240 volts single-phase. This provides 120V for standard outlets and lighting, and 240V for large appliances like ranges, dryers, and air conditioners.
QUESTION 2 OF 50
What is the minimum burial depth for rigid metal conduit (RMC) under a residential driveway subject to automobile traffic?
✓ Correct Answer: A) 6 inches
Per NEC Table 300.5, rigid metal conduit (RMC) requires only 6 inches of burial depth under driveways and areas subject to automobile traffic due to its robust construction.
QUESTION 3 OF 50
How many 12 AWG THHN conductors are permitted in a 1/2-inch EMT conduit?
✓ Correct Answer: B) 9
According to NEC Annex C, Table C.1, a 1/2-inch EMT conduit can hold 9 conductors of 12 AWG THHN wire at 40% fill.
QUESTION 4 OF 50
What is the ampacity of a 10 AWG copper conductor with THHN insulation in an ambient temperature of 30°C (86°F)?
✓ Correct Answer: D) 35 amperes
Per NEC Table 310.16 (now 310.15(B)(16)), 10 AWG copper THHN conductor has an ampacity of 35 amperes in the 75°C column, which is the standard for most terminations.
QUESTION 5 OF 50
GFCI protection is required for all 125-volt, single-phase, 15- and 20-ampere receptacles installed in which location?
✓ Correct Answer: C) Bathrooms
Per NEC 210.8(A)(1), all 125V, 15A and 20A receptacles installed in bathrooms require GFCI protection to prevent electric shock in wet locations.
QUESTION 6 OF 50
What is the maximum distance between receptacle outlets along a wall in a residential dwelling?
✓ Correct Answer: C) 12 feet
NEC 210.52(A) requires receptacles to be installed so that no point along the wall is more than 6 feet from a receptacle, meaning receptacles can be spaced up to 12 feet apart.
QUESTION 7 OF 50
The grounded conductor in a circuit is typically identified by what color?
✓ Correct Answer: B) White or gray
Per NEC 200.6, grounded conductors (neutral) must be identified by white or gray insulation, or by three continuous white stripes on insulation other than green.
QUESTION 8 OF 50
What is the minimum working space clearance required in front of a 120/240V electrical panel with exposed live parts?
✓ Correct Answer: B) 3 feet
NEC 110.26(A)(1) requires a minimum working space of 3 feet (36 inches) in front of electrical equipment rated 600V or less with exposed live parts.
QUESTION 9 OF 50
A 15-ampere, 120-volt circuit can safely supply how many watts of continuous load?
✓ Correct Answer: B) 1,440 watts
Continuous loads must not exceed 80% of the circuit rating. 15A × 120V = 1,800W total capacity. 1,800W × 0.80 = 1,440W maximum continuous load per NEC 210.20(A).
QUESTION 10 OF 50
What size copper grounding electrode conductor is required for a 200-ampere service with 3/0 AWG service entrance conductors?
✓ Correct Answer: C) 4 AWG
Per NEC Table 250.66, for service entrance conductors of 3/0 AWG copper, the grounding electrode conductor must be 4 AWG copper minimum.
QUESTION 11 OF 50
At what height above the finished floor should wall switches generally be mounted?
✓ Correct Answer: C) 48 inches
While not strictly mandated by the NEC, standard practice is to mount wall switches at 48 inches (4 feet) to the center of the switch box. ADA requirements for accessible switches require a maximum height of 48 inches.
QUESTION 12 OF 50
What is the minimum number of lighting outlets required in a bathroom?
✓ Correct Answer: B) At least one wall-switched lighting outlet
Per NEC 210.70(A)(1), at least one wall-switched lighting outlet is required in bathrooms and other habitable rooms.
QUESTION 13 OF 50
What is the maximum voltage drop recommended for branch circuits according to the NEC?
✓ Correct Answer: B) 3%
NEC 210.19(A)(1) FPN No. 4 recommends limiting voltage drop on branch circuits to 3% for efficiency, with a combined feeder and branch circuit maximum of 5%.
QUESTION 14 OF 50
Junction boxes must be installed so that the wiring is accessible without:
✓ Correct Answer: A) Removing permanent finish materials
Per NEC 314.29, junction boxes must remain accessible without removing any part of the building structure or finish. They cannot be covered by drywall, tile, or other permanent materials.
QUESTION 15 OF 50
What is the required minimum size equipment grounding conductor for a 20-ampere circuit using copper conductors?
✓ Correct Answer: B) 12 AWG
According to NEC Table 250.122, the minimum equipment grounding conductor for a 20-ampere overcurrent device is 12 AWG copper.
QUESTION 16 OF 50
How many small appliance branch circuits are required in a dwelling unit kitchen?
✓ Correct Answer: B) 2 circuits
Per NEC 210.11(C)(1), at least two 20-ampere small appliance branch circuits are required to serve receptacles in the kitchen, dining room, breakfast room, and pantry.
QUESTION 17 OF 50
What is the maximum overcurrent protection allowed for 12 AWG copper conductors?
✓ Correct Answer: B) 20 amperes
Per NEC 240.4(D), the maximum overcurrent protection for 12 AWG copper conductors is 20 amperes, even though the wire has a 25A ampacity.
QUESTION 18 OF 50
Within how many inches of a bathroom basin must at least one receptacle be located?
✓ Correct Answer: C) 36 inches
Per NEC 210.52(D), at least one receptacle must be installed within 3 feet (36 inches) of the outside edge of each bathroom basin.
QUESTION 19 OF 50
What is the minimum conductor size for general purpose branch circuits?
✓ Correct Answer: C) 14 AWG
Per NEC 210.19(A), the minimum conductor size for branch circuits is 14 AWG copper (or 12 AWG aluminum).
QUESTION 20 OF 50
What is the required clearance for overhead power lines above a swimming pool?
✓ Correct Answer: D) 22.5 feet
Per NEC 680.8, overhead conductors must be at least 22.5 feet above the maximum water level of a pool for voltages up to 15kV.
QUESTION 21 OF 50
All receptacles within how many feet of a swimming pool require GFCI protection?
✓ Correct Answer: D) 20 feet
Per NEC 680.22(A)(3), all 125V receptacles located within 20 feet of the inside walls of a pool must be protected by a GFCI.
QUESTION 22 OF 50
How many cubic inches does a 14 AWG conductor require when calculating box fill?
✓ Correct Answer: B) 2.0 cubic inches
Per NEC Table 314.16(B), each 14 AWG conductor requires 2.0 cubic inches of box volume for calculating box fill.
QUESTION 23 OF 50
Type NM cable must be supported at intervals not exceeding:
✓ Correct Answer: C) 4.5 feet
Per NEC 334.30, Type NM cable must be supported at intervals not exceeding 4.5 feet and within 12 inches of boxes and cabinets.
QUESTION 24 OF 50
What is the standard frequency of AC power in the United States?
✓ Correct Answer: B) 60 Hz
The standard frequency for alternating current in the United States is 60 Hertz (cycles per second), unlike many other countries that use 50 Hz.
QUESTION 25 OF 50
What percentage of continuous load must circuit breakers be rated for?
✓ Correct Answer: C) 125%
Per NEC 210.20(A), overcurrent protection devices must be rated at 125% of continuous loads (or the continuous load cannot exceed 80% of the breaker rating).
QUESTION 26 OF 50
What is the minimum depth of working space required in front of a panelboard?
✓ Correct Answer: C) 36 inches
Per NEC 110.26(A)(1), the minimum depth of working space in front of electrical equipment rated 600V or less is 3 feet (36 inches).
QUESTION 27 OF 50
Arc-fault circuit interrupter (AFCI) protection is required for branch circuits supplying outlets in:
✓ Correct Answer: C) Bedrooms
Per NEC 210.12(A), all 120V, 15A and 20A branch circuits supplying outlets in dwelling unit bedrooms require AFCI protection. Recent code editions have expanded this to include most living areas.
QUESTION 28 OF 50
What is the maximum height for the center of the operating handle of a disconnect switch?
✓ Correct Answer: C) 6 feet 7 inches
Per NEC 404.8(A), the center of the grip of the operating handle of a switch or circuit breaker must not exceed 6 feet 7 inches (2.0 meters) above the floor.
QUESTION 29 OF 50
What is the minimum lighting load calculation for dwelling units per square foot?
✓ Correct Answer: B) 3 VA per square foot
Per NEC Table 220.12, the minimum lighting load for dwelling units is 3 volt-amperes per square foot of floor area.
QUESTION 30 OF 50
Tamper-resistant receptacles are required in which locations?
✓ Correct Answer: B) All dwelling unit receptacles
Per NEC 406.12, all 125V, 15A and 20A receptacles in dwelling units must be tamper-resistant to prevent children from inserting objects into them.
QUESTION 31 OF 50
What is the minimum size copper wire required for a 50-ampere circuit?
✓ Correct Answer: B) 6 AWG
Per NEC Table 310.16 (75°C column), 6 AWG copper conductor has an ampacity of 65 amperes, which is sufficient for a 50-ampere circuit.
QUESTION 32 OF 50
What color must equipment grounding conductors be?
✓ Correct Answer: C) Green or green with yellow stripe
Per NEC 250.119, equipment grounding conductors must be identified by green color, green with one or more yellow stripes, or bare copper.
QUESTION 33 OF 50
What is the minimum number of outdoor receptacles required for a one-family dwelling?
✓ Correct Answer: C) 2 receptacles
Per NEC 210.52(E), at least two receptacle outlets are required outdoors for one-family dwellings - one in front and one in back.
QUESTION 34 OF 50
EMT (electrical metallic tubing) must be supported at intervals not exceeding:
✓ Correct Answer: C) 10 feet
Per NEC 358.30(A), EMT must be securely fastened at intervals not exceeding 10 feet, and within 3 feet of each outlet box or fitting.
QUESTION 35 OF 50
What is the minimum wire bending space at terminals for 4 AWG conductors?
✓ Correct Answer: D) 3 inches
Per NEC Table 312.6(A), the minimum wire bending space for 4 AWG conductors at terminals is 3 inches.
QUESTION 36 OF 50
A 240-volt circuit serving an electric water heater requires what minimum size copper conductors?
✓ Correct Answer: D) Depends on water heater rating
The conductor size depends on the water heater's ampacity rating. The conductors must be sized at 125% of the water heater rating per NEC 422.13.
QUESTION 37 OF 50
What is the maximum number of quarter bends (90° bends) allowed in a conduit run between pull points?
✓ Correct Answer: C) 4
Per NEC 358.26, a conduit run may not contain more than the equivalent of four quarter bends (360° total) between pull points.
QUESTION 38 OF 50
Luminaires installed in clothes closets must maintain how much clearance from storage space?
✓ Correct Answer: B) 12 inches
Per NEC 410.16(C), surface-mounted incandescent or LED luminaires in closets must maintain at least 12 inches clearance from the storage space.
QUESTION 39 OF 50
What is the minimum burial depth for PVC conduit (Schedule 80) under a residential driveway?
✓ Correct Answer: C) 18 inches
Per NEC Table 300.5, rigid nonmetallic conduit (PVC) requires 18 inches burial depth under driveways and areas subject to vehicular traffic.
QUESTION 40 OF 50
Receptacles installed outdoors in a wet location must be:
✓ Correct Answer: B) Listed for wet locations with covers
Per NEC 406.9(A), receptacles in wet locations must be listed for that use and have weatherproof covers that maintain protection whether or not a plug is inserted.
QUESTION 41 OF 50
What is the minimum number of lighting circuits required for a 2,400 square foot dwelling?
✓ Correct Answer: B) 4 circuits
2,400 sq ft × 3 VA = 7,200 VA. At 120V: 7,200 ÷ 120 = 60A needed. 60A ÷ 15A per circuit = 4 circuits minimum per NEC 220.12.
QUESTION 42 OF 50
Flexible metal conduit (FMC) is permitted as an equipment grounding conductor when the total length does not exceed:
✓ Correct Answer: C) 6 feet
Per NEC 250.118(5), FMC is acceptable as an equipment grounding conductor when the length does not exceed 6 feet and the circuit is protected at 20 amperes or less.
QUESTION 43 OF 50
When must a disconnecting means be provided for an air conditioning unit?
✓ Correct Answer: B) Within sight of the unit
Per NEC 440.14, a disconnecting means must be located within sight from and readily accessible from the air conditioning equipment.
QUESTION 44 OF 50
What is the minimum width of working space required in front of a panelboard?
✓ Correct Answer: B) 30 inches
Per NEC 110.26(A)(2), the minimum width of working space in front of electrical equipment must be 30 inches or the width of the equipment, whichever is greater.
QUESTION 45 OF 50
Receptacles in a garage of a dwelling unit must be protected by:
✓ Correct Answer: B) GFCI only
Per NEC 210.8(A)(2), all 125V, 15A and 20A receptacles installed in garages require GFCI protection. AFCI protection is not required for garage receptacles.
QUESTION 46 OF 50
What is the minimum height above grade for service drop conductors over residential driveways?
✓ Correct Answer: B) 12 feet
Per NEC 230.24(B)(1), service drop conductors must maintain a minimum clearance of 12 feet above residential property and driveways.
QUESTION 47 OF 50
Smoke alarms must be powered by which of the following?
✓ Correct Answer: B) 120V branch circuit with battery backup
Per NEC 210.12(D) and building codes, smoke alarms in new construction must receive power from a 120V branch circuit and have battery backup for continued operation during power outages.
QUESTION 48 OF 50
What is the minimum headroom clearance for working spaces around service equipment?
✓ Correct Answer: B) 6.5 feet
Per NEC 110.26(A)(3), the minimum headroom of working spaces around service equipment and panelboards must be 6.5 feet or the height of the equipment, whichever is greater.
QUESTION 49 OF 50
Underground service lateral conductors must have a minimum burial depth of:
✓ Correct Answer: D) 24 inches
Per NEC 230.49, underground service lateral conductors must have a minimum burial depth of 24 inches, unless they meet the conditions for shallower burial as specified in Table 300.5.
QUESTION 50 OF 50
What is the standard color coding for a three-phase, 4-wire delta system with a high leg?
✓ Correct Answer: B) Black, Orange (high leg), Blue, White
Per NEC 110.15 and 408.3(E), the high leg of a 4-wire delta system must be identified by orange color or other effective means at all points where connections are made. Common practice is Black, Orange (high leg), Blue for phase conductors, and White for neutral.