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WI Electrician practice questions

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Question 1Electrical Trade Knowledge (Journeyman Electrician)

The minimum working clearance in front of a 480-volt panelboard with exposed live parts on one side and no live or grounded parts on the other side is:

  1. 3 feet Correct answer.
  2. 4 feet
  3. 5 feet
  4. 6 feet

Explanation

NEC Table 110.26(A)(1) requires a minimum of 3 feet of working space for equipment operating at 150 to 600 volts to ground where the opposite side has no live or grounded parts. Greater depths are required when the opposite side is grounded or live.

Question 2Electrical Trade Knowledge (Journeyman Electrician)

A 20-ampere branch circuit supplying a single receptacle in a dwelling unit is protected by a 20-ampere breaker. What is the minimum allowable receptacle rating?

  1. 20 ampere Correct answer.
  2. 50 ampere
  3. 15 ampere
  4. 30 ampere

Explanation

NEC 210.21(B)(1) requires a single receptacle on an individual branch circuit to have an ampere rating not less than that of the branch circuit. A 20-ampere circuit therefore needs at least a 20-ampere receptacle.

Question 3Electrical Trade Knowledge (Journeyman Electrician)

The grounded conductor of a 120/240-volt single-phase residential service is required to be which color?

  1. Red
  2. Black
  3. White or gray Correct answer.
  4. Green

Explanation

NEC 200.6 requires the grounded conductor to be identified by a continuous white or gray finish. Green is reserved for equipment grounding conductors, and black and red are ungrounded conductors.

Question 4Electrical Trade Knowledge (Journeyman Electrician)

A general-use snap switch controlling a 120-volt lighting circuit must be rated at not less than:

  1. 250 volts and 20 amperes
  2. 120 volts and 15 amperes Correct answer.
  3. 120 volts and 10 amperes
  4. 125 volts and 15 amperes

Explanation

NEC 404.14 and 404.2 require switches to have a voltage rating not less than the circuit voltage and an ampere rating adequate for the load. Standard 15-ampere switches rated 120 volts satisfy the minimum for a 120-volt general lighting circuit.

Question 5Electrical Trade Knowledge (Journeyman Electrician)

Which of the following best describes the purpose of the equipment grounding conductor?

  1. It reduces the voltage drop on long circuits.
  2. It carries normal operating current back to the source.
  3. It balances voltage between phases.
  4. It provides a low-impedance path for fault current to facilitate overcurrent device operation. Correct answer.

Explanation

The equipment grounding conductor bonds metal enclosures to the system grounding point so that a ground fault produces a low-impedance path that trips the overcurrent device. It does not normally carry current.

Question 6Electrical Trade Knowledge (Journeyman Electrician)

A 240-volt, 40-ampere continuous load is supplied by a branch circuit. What is the minimum conductor ampacity required before any adjustment factors?

  1. 32 amperes
  2. 40 amperes
  3. 60 amperes
  4. 50 amperes Correct answer.

Explanation

NEC 210.19(A)(1) requires branch-circuit conductors to have an ampacity of at least 125 percent of a continuous load. 40 amperes times 1.25 equals 50 amperes.

Question 7Electrical Trade Knowledge (Journeyman Electrician)

A dwelling unit has a 3,000 square foot floor area. Using the general lighting load of 3 volt-amperes per square foot, what is the general lighting load before demand factors?

  1. 6,000 volt-amperes
  2. 9,000 volt-amperes Correct answer.
  3. 12,000 volt-amperes
  4. 15,000 volt-amperes

Explanation

NEC Table 220.12 specifies 3 volt-amperes per square foot for dwelling units. Multiplying 3,000 square feet by 3 VA per square foot gives 9,000 volt-amperes.

Question 8Electrical Trade Knowledge (Journeyman Electrician)

A conductor with a 90 degrees C insulation rating is installed in an ambient temperature of 50 degrees C. What correction factor applies to its ampacity?

  1. 0.91
  2. 0.82 Correct answer.
  3. 0.88
  4. 1.00

Explanation

NEC Table 310.15(B)(2)(a) lists an ambient correction factor of 0.82 for 90 degrees C conductors at 50 degrees C. The factor reduces ampacity to account for the higher operating temperature.

Question 9Electrical Trade Knowledge (Journeyman Electrician)

The minimum size copper equipment grounding conductor for a 100-ampere overcurrent device protecting a feeder is:

  1. 12 AWG
  2. 10 AWG
  3. 8 AWG Correct answer.
  4. 14 AWG

Explanation

NEC Table 250.122 requires an 8 AWG copper equipment grounding conductor for overcurrent devices rated up to 100 amperes. The size scales with the overcurrent device, not the phase conductor.

Question 10Electrical Trade Knowledge (Journeyman Electrician)

A 120-volt circuit has a load drawing 12 amperes. What is the approximate voltage drop if the round-trip conductor length is 100 feet of 12 AWG copper (approximately 0.00193 ohms per foot)?

  1. 12 volts
  2. 2.3 volts Correct answer.
  3. 4.6 volts
  4. 1.2 volts

Explanation

Voltage drop equals current times total conductor resistance. Using 100 feet of 12 AWG at about 0.00193 ohms per foot, the resistance is 0.193 ohms, so drop is 12 amperes times 0.193 ohms, roughly 2.3 volts.

Question 11Electrical Trade Knowledge (Journeyman Electrician)

In a 3-phase, 4-wire, 208Y/120-volt system, the voltage between any two ungrounded conductors is:

  1. 240 volts
  2. 208 volts Correct answer.
  3. 277 volts
  4. 120 volts

Explanation

In a wye-connected system, the line-to-line voltage equals the line-to-neutral voltage multiplied by the square root of three. 120 volts times 1.732 equals approximately 208 volts.

Question 12Electrical Trade Knowledge (Journeyman Electrician)

A motor branch circuit uses an inverse-time circuit breaker for short-circuit protection. For a motor with a full-load current of 20 amperes, what is the maximum standard rating permitted for the breaker?

  1. 40 amperes
  2. 60 amperes Correct answer.
  3. 50 amperes
  4. 80 amperes

Explanation

NEC Table 430.52 permits an inverse-time circuit breaker up to 250 percent of the motor full-load current for a standard rating. 20 amperes times 2.5 equals 50 amperes, and the next standard rating of 60 amperes may be used when 50 amperes does not correspond to a standard size.

Question 13Electrical Trade Knowledge (Journeyman Electrician)

A 15-ampere, 125-volt receptacle is installed on a 20-ampere branch circuit in a dwelling. Which statement is correct about the circuit?

  1. The circuit must have at least two receptacles. Correct answer.
  2. The circuit must be protected at 15 amperes.
  3. The circuit may supply only one receptacle.
  4. The circuit must use 10 AWG conductors.

Explanation

NEC 210.21(B)(3) permits 15-ampere receptacles on a 20-ampere circuit only when the circuit supplies two or more receptacles. A single receptacle must match the circuit rating.

Question 14Electrical Trade Knowledge (Journeyman Electrician)

The minimum number of 20-ampere small-appliance branch circuits required in a dwelling unit kitchen is:

  1. 1
  2. 4
  3. 2 Correct answer.
  4. 3

Explanation

NEC 210.11(C)(1) requires at least two 20-ampere small-appliance branch circuits for the kitchen, pantry, and similar areas. These circuits supply receptacle outlets for countertop appliances.

Question 15Electrical Trade Knowledge (Journeyman Electrician)

A box is required to contain a total of 8 conductors of 12 AWG. Using Table 314.16(B), what is the minimum box volume by conductor count?

  1. 20 cubic inches
  2. 16 cubic inches Correct answer.
  3. 24 cubic inches
  4. 18 cubic inches

Explanation

NEC Table 314.16(B) assigns 2.25 cubic inches per 12 AWG conductor. Eight conductors times 2.25 equals 18 cubic inches.

Question 16Electrical Trade Knowledge (Journeyman Electrician)

Which of the following is the correct minimum burial depth for direct-buried UF cable supplying a dwelling unit?

  1. 24 inches Correct answer.
  2. 12 inches
  3. 18 inches
  4. 30 inches

Explanation

NEC Table 300.5 requires a minimum cover of 24 inches for direct-buried cable in a residential application. Deeper cover is required under roadways and other special conditions.

Question 17Electrical Trade Knowledge (Journeyman Electrician)

A 60-ampere, 240-volt single-phase feeder supplies a subpanel. The conductors are copper THWN in a raceway. What is the minimum conductor size required for the ungrounded conductors, assuming terminations rated 75 degrees C?

  1. 2 AWG
  2. 4 AWG
  3. 8 AWG
  4. 6 AWG Correct answer.

Explanation

NEC Table 310.16 shows 6 AWG copper at 75 degrees C has an ampacity of 65 amperes, which exceeds the 60-ampere feeder requirement. 8 AWG at 75 degrees C is only 50 amperes.

Question 18Electrical Trade Knowledge (Journeyman Electrician)

A luminaire is installed in a clothes closet. Which location is permitted for a surface-mounted incandescent fixture?

  1. On the wall above the door Correct answer.
  2. Within 12 inches of the shelf edge
  3. Directly above the shelf
  4. Inside the closet storage area

Explanation

NEC 410.16 permits surface-mounted incandescent or LED luminaires on the wall above the door in a clothes closet. Luminaires are restricted from the storage area near shelves.

Question 19Electrical Trade Knowledge (Journeyman Electrician)

A 3-phase, 480-volt motor has a nameplate full-load current of 34 amperes. What is the minimum size copper conductor required for the branch circuit, using 75 degrees C terminations?

  1. 6 AWG
  2. 8 AWG Correct answer.
  3. 4 AWG
  4. 10 AWG

Explanation

NEC 430.22 requires motor branch-circuit conductors to have an ampacity of at least 125 percent of the full-load current. 34 amperes times 1.25 equals 42.5 amperes, and 8 AWG copper at 75 degrees C is rated 50 amperes.

Question 20Electrical Trade Knowledge (Journeyman Electrician)

When calculating the neutral load for a 120/240-volt single-phase service, the neutral conductor is permitted to be reduced based on:

  1. The total of both ungrounded conductor loads
  2. The larger of the two ungrounded conductor loads
  3. The smaller of the two ungrounded conductor loads Correct answer.
  4. The average of the two ungrounded conductor loads

Explanation

NEC 220.61 permits the neutral load to be based on the maximum unbalanced load, which for a single-phase system is the smaller of the two ungrounded conductor loads. The neutral need not carry the full total.

Question 21Electrical Trade Knowledge (Journeyman Electrician)

A ground-fault circuit interrupter is required for receptacles installed in which of the following dwelling unit locations?

  1. A living room
  2. A hallway
  3. A bedroom
  4. A bathroom Correct answer.

Explanation

NEC 210.8(A) requires GFCI protection for receptacles in bathrooms, kitchens, garages, outdoors, and other specified wet or damp locations. Bathrooms are a classic required location.

Question 22Electrical Trade Knowledge (Journeyman Electrician)

A 50-ampere electric range is supplied by a 120/240-volt branch circuit. Using Table 220.55, the minimum demand for one range rated 8 kW is:

  1. 4 kW
  2. 8 kW Correct answer.
  3. 3 kW
  4. 6 kW

Explanation

NEC Table 220.55 permits a demand of 8 kW for a single range rated 8 kW or less. The full nameplate value is used at this rating.

Question 23Electrical Trade Knowledge (Journeyman Electrician)

The service disconnecting means for a one-family dwelling must be installed in a readily accessible location that is:

  1. Nearest the point of entrance of the service conductors Correct answer.
  2. At the property line
  3. In the basement only
  4. Inside the attic

Explanation

NEC 230.70 requires the service disconnecting means to be installed at a readily accessible location nearest the point of entrance of the service conductors. This minimizes the length of unprotected service conductors inside the building.

Question 24Electrical Trade Knowledge (Journeyman Electrician)

A 120-volt, 15-ampere branch circuit uses 14 AWG copper conductors. What is the maximum permissible overcurrent protection?

  1. 15 amperes Correct answer.
  2. 10 amperes
  3. 30 amperes
  4. 20 amperes

Explanation

NEC 240.4(D) limits 14 AWG copper conductors to 15-ampere overcurrent protection. Larger breakers would allow the conductor to overheat before the device trips.

Question 25Electrical Trade Knowledge (Journeyman Electrician)

In a 3-phase system, a balanced 208-volt load draws 30 amperes per phase. What is the approximate apparent power?

  1. 6.2 kVA
  2. 18.7 kVA
  3. 10.8 kVA Correct answer.
  4. 24.0 kVA

Explanation

Three-phase apparent power equals the square root of three times voltage times current. 1.732 times 208 volts times 30 amperes equals approximately 10.8 kVA.

Question 26Electrical Trade Knowledge (Journeyman Electrician)

Which conductor color is commonly used to identify the grounded (neutral) conductor of a branch circuit in a typical wiring method?

  1. Red
  2. Green
  3. Black
  4. White or gray Correct answer.

Explanation

The NEC requires the grounded conductor to be identified by a continuous white or gray finish, or by three continuous white stripes on other than green insulation. Green is reserved for equipment grounding conductors, and black and red are typically ungrounded (hot) conductors.

Question 27Electrical Trade Knowledge (Journeyman Electrician)

A single-phase, 120-volt branch circuit supplies a 1,500-watt resistive load. What is the approximate current drawn by the load?

  1. 12.5 amperes Correct answer.
  2. 10.0 amperes
  3. 15.0 amperes
  4. 18.0 amperes

Explanation

For a resistive load, current equals power divided by voltage (I = P / E). Dividing 1,500 watts by 120 volts gives 12.5 amperes.

Question 28Electrical Trade Knowledge (Journeyman Electrician)

What is the primary purpose of bonding metal raceways and equipment enclosures together?

  1. To reduce the operating temperature of the conductors
  2. To increase the voltage available at the load
  3. To provide a low-impedance path that allows overcurrent devices to clear a fault Correct answer.
  4. To carry the normal load current back to the source

Explanation

Bonding creates an effective ground-fault current path so that a fault will draw enough current to open the overcurrent protective device quickly. This limits dangerous voltage on metal parts during a fault.

Question 29Electrical Trade Knowledge (Journeyman Electrician)

A luminaire is installed over a bathtub. Which condition makes the installation acceptable?

  1. The luminaire is listed for a damp or wet location and is installed at least 8 feet above the top of the tub rim Correct answer.
  2. The luminaire is cord-connected and hangs within reach of the tub
  3. The luminaire is a standard open incandescent fixture mounted 6 feet above the tub rim
  4. The luminaire is surface-mounted on the ceiling 7 feet above the tub rim

Explanation

Luminaires in a bathtub or shower zone must be suitable for the location and, where subject to shower spray, must be listed for wet locations; fixtures must be positioned so they are not within the restricted zone near the tub. A listed damp/wet-location fixture mounted at least 8 feet above the tub rim satisfies these requirements.

Question 30Electrical Trade Knowledge (Journeyman Electrician)

A 20-ampere branch circuit supplies a single receptacle outlet in a commercial occupancy. What is the minimum rating of the receptacle?

  1. 20 amperes Correct answer.
  2. 10 amperes
  3. 15 amperes
  4. 30 amperes

Explanation

A single receptacle on an individual branch circuit must have an ampere rating not less than the branch-circuit rating. On a 20-ampere circuit, the receptacle must therefore be rated at least 20 amperes.

Question 31Electrical Trade Knowledge (Journeyman Electrician)

An appliance nameplate shows 240 volts and 4,800 watts. What is the minimum branch-circuit conductor ampacity, treating the appliance as a continuous load at 125 percent?

  1. 25 amperes Correct answer.
  2. 20 amperes
  3. 24 amperes
  4. 30 amperes

Explanation

First find the load current: 4,800 watts divided by 240 volts equals 20 amperes. For a continuous load, the branch-circuit conductors must be sized at 125 percent of the load, so 20 amperes times 1.25 equals 25 amperes.

Question 32Electrical Trade Knowledge (Journeyman Electrician)

A feeder supplies a continuous load of 80 amperes and a noncontinuous load of 40 amperes. What is the minimum feeder overcurrent device rating?

  1. 150 amperes
  2. 140 amperes Correct answer.
  3. 160 amperes
  4. 120 amperes

Explanation

The feeder must be sized for 125 percent of the continuous load plus 100 percent of the noncontinuous load: (80 × 1.25) + 40 = 100 + 40 = 140 amperes.

Question 33Electrical Trade Knowledge (Journeyman Electrician)

A rigid metal conduit run is installed outdoors in direct sunlight where the ambient temperature reaches 40 degrees C. The conductors are rated 75 degrees C. Which ampacity adjustment applies?

  1. Apply only the conduit fill adjustment, not temperature correction
  2. Apply the ambient temperature correction factor from the ampacity tables for 40 degrees C Correct answer.
  3. Apply a correction factor for 30 degrees C
  4. No adjustment is needed because the conductors are in a raceway

Explanation

Conductor ampacity must be corrected for ambient temperature whenever the ambient exceeds the table base temperature of 30 degrees C. The 40 degrees C ambient requires the appropriate correction factor for the conductor's insulation rating.

Question 34Electrical Trade Knowledge (Journeyman Electrician)

What is the minimum working clearance in front of a 480-volt panelboard with exposed live parts on one side and no live parts or grounded surfaces on the other side?

  1. 4 feet
  2. 6 feet
  3. 3 feet Correct answer.
  4. 2 feet

Explanation

For equipment operating at 480 volts with exposed live parts on one side and no live or grounded parts on the opposite side, the minimum depth of the working space is 3 feet. Greater depths are required when grounded or live surfaces are opposite.

Question 35Electrical Trade Knowledge (Journeyman Electrician)

A 3-phase, 480-volt feeder supplies a load of 60 amperes. What is the approximate apparent power?

  1. 25 kVA
  2. 75 kVA
  3. 50 kVA Correct answer.
  4. 100 kVA

Explanation

For a three-phase load, apparent power equals the square root of 3 times voltage times current. Multiplying 1.732 × 480 volts × 60 amperes gives approximately 49,900 volt-amperes, or about 50 kVA.

Question 36Electrical Trade Knowledge (Journeyman Electrician)

A conductor must be spliced inside a box. Which method is acceptable for a copper-to-copper splice in a dry location?

  1. Twisting and wrapping with friction tape only
  2. A listed pressure connector or a listed splicing device Correct answer.
  3. Soldering alone without a mechanical connector
  4. Twisting the conductors together and covering with electrical tape

Explanation

Splices must be made with listed splicing devices or by an approved means that provides a secure connection. Pressure connectors and listed splicing devices are acceptable; bare twisting or tape alone is not.

Question 37Electrical Trade Knowledge (Journeyman Electrician)

A 120/240-volt single-phase service supplies a dwelling. The calculated unbalanced neutral load is 90 amperes. What is the minimum permitted neutral conductor ampacity?

  1. 70 amperes
  2. 45 amperes
  3. 120 amperes
  4. 90 amperes Correct answer.

Explanation

The neutral must be sized to carry the maximum unbalanced load, which here is 90 amperes. Reduction is permitted only where the calculated unbalanced load allows it, and the neutral may not be smaller than the calculated value.

Question 38Electrical Trade Knowledge (Journeyman Electrician)

A 240-volt, 30-ampere branch circuit supplies a fixed electric space-heating unit. What is the minimum conductor ampacity required for this continuous load?

  1. 30 amperes
  2. 45 amperes
  3. 37.5 amperes Correct answer.
  4. 24 amperes

Explanation

Fixed electric space-heating equipment is a continuous load, so branch-circuit conductors must be sized at 125 percent of the load current. Multiplying 30 amperes by 1.25 gives 37.5 amperes.

Question 39Electrical Trade Knowledge (Journeyman Electrician)

A grounding electrode conductor is installed to a metal water pipe. Where must the connection be made?

  1. Anywhere downstream of the water meter inside the building
  2. At the water heater inlet
  3. On the street side of the water meter, or on the building side where the pipe is not removable Correct answer.
  4. On the cold-water line after any plastic transition fitting

Explanation

The grounding electrode connection to a metal water pipe must be made on the street side of the water meter, or on the building side where the piping is not likely to be removed. This ensures a continuous grounding path.

Question 40Electrical Trade Knowledge (Journeyman Electrician)

A 15-ampere branch circuit uses 14 AWG copper conductors. What is the maximum standard overcurrent device rating permitted to protect these conductors?

  1. 25 amperes
  2. 20 amperes
  3. 15 amperes Correct answer.
  4. 30 amperes

Explanation

14 AWG copper conductors have an ampacity of 15 amperes, and the overcurrent device may not exceed the conductor ampacity except under specific permitted conditions. A 15-ampere device is the maximum standard rating for a general 14 AWG circuit.

Question 41Electrical Trade Knowledge (Master Electrician)

According to the NEC, what is the maximum permitted voltage drop for a branch circuit plus feeder combined?

  1. 10 percent
  2. 5 percent Correct answer.
  3. 2 percent
  4. 3 percent

Explanation

NEC 210.19(A) Informational Note No. 4 and 215.2(A)(1) Informational Note No. 2 recommend that the total voltage drop for feeders plus branch circuits not exceed 5 percent. This is a recommended limit, not a mandatory requirement in most cases.

Question 42Electrical Trade Knowledge (Master Electrician)

What is the minimum required working space depth in front of a 480-volt panelboard with exposed live parts on one side, where the opposite side is a concrete wall?

  1. 4 feet Correct answer.
  2. 6 feet
  3. 3 feet
  4. 5 feet

Explanation

NEC Table 110.26(A)(1) requires a minimum depth of 4 feet for equipment operating at 151 to 600 volts to ground where there are exposed live parts on one side and no live parts or grounded surfaces on the other side. A concrete wall counts as a grounded surface but does not increase the required depth beyond the base condition.

Question 43Electrical Trade Knowledge (Master Electrician)

Which of the following is the correct color code for the grounded conductor in a 120/240-volt single-phase system?

  1. Black
  2. White or gray Correct answer.
  3. Green
  4. Red

Explanation

NEC 200.6 requires the grounded conductor to be identified by a continuous white or gray outer finish along its entire length. Green is reserved for equipment grounding conductors, and black and red are typically ungrounded (hot) conductors.

Question 44Electrical Trade Knowledge (Master Electrician)

A 20-ampere branch circuit supplies a single receptacle. What is the minimum allowable ampere rating of that receptacle?

  1. 15 amperes
  2. 20 amperes Correct answer.
  3. 30 amperes
  4. 10 amperes

Explanation

NEC 210.21(B)(1) requires that a single receptacle on an individual branch circuit have an ampere rating not less than that of the branch circuit. Therefore, a 20-ampere circuit requires a 20-ampere receptacle.

Question 45Electrical Trade Knowledge (Master Electrician)

What is the maximum overcurrent protection permitted for a 14 AWG copper conductor in a residential branch circuit?

  1. 25 amperes
  2. 20 amperes
  3. 10 amperes
  4. 15 amperes Correct answer.

Explanation

NEC 240.4(D) limits 14 AWG copper to 15 amperes overcurrent protection for most applications. This is a standard small-conductor rule that applies regardless of the conductor's ampacity in free air.

Question 46Electrical Trade Knowledge (Master Electrician)

In a 3-phase, 4-wire, 208Y/120-volt system, what is the voltage between any two ungrounded conductors?

  1. 120 volts
  2. 208 volts Correct answer.
  3. 240 volts
  4. 277 volts

Explanation

In a 208Y/120-volt wye system, the line-to-line voltage is the phase voltage (120 V) multiplied by the square root of 3, which equals approximately 208 volts. The 120-volt value is the line-to-neutral voltage.

Question 47Electrical Trade Knowledge (Master Electrician)

What is the minimum cover requirement for rigid metal conduit installed under a street or roadway?

  1. 6 inches
  2. 18 inches
  3. 30 inches
  4. 24 inches Correct answer.

Explanation

NEC Table 300.5 requires a minimum cover of 24 inches for rigid metal conduit under streets, highways, roads, alleys, driveways, and parking lots. This depth protects the conduit from traffic loads.

Question 48Electrical Trade Knowledge (Master Electrician)

A continuous load of 40 amperes is supplied by a branch circuit with no other loads. What is the minimum branch-circuit conductor ampacity required before any adjustment factors?

  1. 50 amperes Correct answer.
  2. 32 amperes
  3. 60 amperes
  4. 40 amperes

Explanation

NEC 210.19(A)(1) requires branch-circuit conductors to have an ampacity not less than 125 percent of the continuous load plus 100 percent of the noncontinuous load. Thus 40 A × 1.25 = 50 A.

Question 49Electrical Trade Knowledge (Master Electrician)

Which of the following wiring methods is permitted in a hoistway?

  1. Type NM cable
  2. Type AC cable
  3. Type SE cable
  4. Rigid metal conduit Correct answer.

Explanation

NEC 620.21 lists acceptable wiring methods for hoistways and machine rooms, including rigid metal conduit, intermediate metal conduit, and electrical metallic tubing. Nonmetallic-sheathed and armored cables are generally not permitted in hoistways.

Question 50Electrical Trade Knowledge (Master Electrician)

What is the maximum number of 12 AWG THHN copper conductors permitted in a 1/2-inch electrical metallic tubing (EMT) with no fittings or boxes?

  1. 20
  2. 12 Correct answer.
  3. 9
  4. 16

Explanation

NEC Chapter 9, Table 1, and Table 5 determine conduit fill. For 1/2-inch EMT, the usable area at 40 percent fill is about 0.122 square inches; each 12 AWG THHN conductor has an area of about 0.0133 square inches, allowing 9 conductors. The total cross-sectional area of 12 THHN conductors slightly exceeds the 40 percent fill, so the correct maximum is 9.