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MA Electrician practice questions

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Question 1General Code Requirements, Definitions, and Administration

The NEC is best described as which of the following?

  1. A design specification for electrical systems
  2. A minimum standard for safeguarding persons and property Correct answer.
  3. A maintenance manual for installed equipment
  4. A product-certification program

Explanation

Section 90.1(A) states that the purpose of the Code is the practical safeguarding of persons and property from hazards arising from the use of electricity, and 90.1(B) notes that it is not intended as a design specification. It establishes minimum installation requirements rather than design guidance, maintenance procedures, or product certification.

Question 2General Code Requirements, Definitions, and Administration

Article 100 defines a "qualified person" as one who has which of the following?

  1. Completion of an OSHA 10-hour construction safety course
  2. Skills, knowledge, and safety training to recognize the hazards Correct answer.
  3. At least four years of documented field experience under a licensed electrician
  4. A current journeyman or master electrician license issued by the state board

Explanation

A qualified person is defined by demonstrated skills and knowledge related to the construction and operation of the electrical equipment and installations, together with safety training to recognize and avoid the hazards involved. A license, a course, or years of service may be evidence of such qualifications but none of them is the definition.

Question 3General Code Requirements, Definitions, and Administration

What is the minimum headroom in the working space about service equipment, switchboards, and panelboards rated 600 volts or less?

  1. 6 ft 6 in Correct answer.
  2. 7 ft 6 in
  3. 7 ft
  4. 6 ft

Explanation

The working space about service equipment, switchboards, panelboards, and motor control centers must have headroom of not less than 1.8 m (6 ft 6 in) measured from the grade, floor, or platform, with the limited exception for existing installations subject to structural constraints.

Question 4General Code Requirements, Definitions, and Administration

The width of the working space in front of electrical equipment must be which of the following?

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

Explanation

The working space in front of electrical equipment must be at least as wide as the equipment itself or 30 in, whichever is greater. The dimension is measured in the direction parallel to the face of the equipment.

Question 5General Code Requirements, Definitions, and Administration

Which Article 100 term means equipment, materials, or services included in a list published by an organization acceptable to the AHJ that maintains periodic inspection of production and states that the equipment meets a recognized standard?

  1. Labeled
  2. Approved
  3. Listed Correct answer.
  4. Identified

Explanation

"Listed" describes equipment, materials, or services included in a list published by an organization acceptable to the AHJ that maintains periodic inspection of production and whose listing states compliance with an appropriate standard or that the item has been tested and found suitable for a specified purpose.

Question 6General Code Requirements, Definitions, and Administration

Section 110.12 requires electrical equipment to be installed in which manner?

  1. In accordance with the engineer's drawings
  2. As directed by the general contractor
  3. In a neat and workmanlike manner Correct answer.
  4. Using only components made in the United States

Explanation

Section 110.12 requires that electrical equipment be installed in a neat and workmanlike manner, and it also prohibits damage to or contamination of internal parts by foreign materials such as paint, plaster, cleaners, or abrasives. Compliance is mandatory, not a matter of preference.

Question 7General Code Requirements, Definitions, and Administration

A panelboard operating at 480Y/277 volts is installed where exposed live parts are on one side of the working space and grounded parts are on the other (condition 2). What is the minimum depth of the working space?

  1. 3 ft
  2. 2 1/2 ft
  3. 4 ft
  4. 3 1/2 ft Correct answer.

Explanation

Table 110.26(A)(1) increases the required depth as the voltage to ground and the conditions on the opposite side of the working space increase. For equipment operating at 151 to 600 volts to ground under condition 2, the minimum depth is 3 1/2 ft.

Question 8General Code Requirements, Definitions, and Administration

Wire-binding screws or studs and nuts with upturned lugs are permitted as a means of connection for conductors of what size and smaller?

  1. 8 AWG
  2. 10 AWG Correct answer.
  3. 6 AWG
  4. 14 AWG

Explanation

Section 110.14(A) permits connection by means of wire-binding screws or studs and nuts with upturned lugs, or the equivalent, for 10 AWG and smaller conductors. Larger conductors require lugs or other approved connection means suited to the conductor.

Question 9General Code Requirements, Definitions, and Administration

What does the Code require of the working space about energized electrical equipment?

  1. Carts may be parked there if they are moved for servicing
  2. The space must be kept clear and not used for storage Correct answer.
  3. Storage is permitted where a warning sign is posted
  4. Storage is permitted while the equipment is de-energized

Explanation

The working space required by 110.26 must be kept clear, and the space may not be used for storage of any kind. The clear space requirement exists so that a person can safely reach and work on the equipment without obstruction.

Question 10General Code Requirements, Definitions, and Administration

Section 110.16 requires a field-applied arc flash hazard warning on which equipment?

  1. Only where the available fault current exceeds 10,000 amperes
  2. Only on service-entrance switchboards and switchgear
  3. Only where the nominal voltage exceeds 1000 volts
  4. Where the equipment may be serviced while energized Correct answer.

Explanation

Section 110.16 applies to equipment such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers that are in other than dwelling units and are likely to require examination, adjustment, servicing, or maintenance while energized. The trigger is the likelihood of energized servicing, not a voltage or fault-current threshold.

Question 11General Code Requirements, Definitions, and Administration

Each disconnecting means must be marked in which way?

  1. With the name of the installing contractor
  2. Legibly, to indicate its purpose Correct answer.
  3. With the available fault current at its terminals
  4. With the date of installation

Explanation

Section 110.22(A) requires each disconnecting means to be legibly marked to indicate its purpose, unless it is located and arranged so that the purpose is evident. The marking tells workers what the disconnect controls before they operate it.

Question 12General Code Requirements, Definitions, and Administration

Equipment intended to interrupt current at fault levels must have an interrupting rating not less than which of the following?

  1. The ampacity of the largest conductor connected to the equipment
  2. The interrupting rating of the next upstream overcurrent device
  3. Twice the nominal system voltage of the circuit supplying it
  4. The available fault current at its line terminals Correct answer.

Explanation

Section 110.9 requires equipment intended to interrupt current at fault levels to have an interrupting rating not less than the nominal circuit voltage and the current that is available at the line terminals of the equipment. A device with an inadequate rating may fail violently when clearing a fault.

Question 13General Code Requirements, Definitions, and Administration

How must terminal connections be tightened under Section 110.14(D)?

  1. With a calibrated torque tool to the marked value Correct answer.
  2. As tight as a standard screwdriver can make them
  3. Finger-tight, then one additional full turn with a wrench
  4. Until the conductor can no longer be moved by hand

Explanation

Section 110.14(D) requires terminal connections to be tightened using a calibrated torque tool to the torque values marked on the equipment or given in the manufacturer's instructions. Both over-tightening and under-tightening are recognized causes of connection failure.

Question 14General Code Requirements, Definitions, and Administration

Article 100 defines an "outlet" as which of the following?

  1. Any point where current is taken to supply equipment Correct answer.
  2. Any lighting fixture or appliance connected to a circuit
  3. The box in which a receptacle is mounted
  4. A device that connects a conductor to a terminal

Explanation

An outlet is any point on the wiring system at which current is taken to supply utilization equipment. The term is broader than a receptacle outlet and includes points that supply luminaires, appliances, and other equipment.

Question 15General Code Requirements, Definitions, and Administration

Under Article 90, the authority having jurisdiction is responsible for which of the following?

  1. Designing the electrical system for the installer
  2. Setting permit fees and inspection schedules
  3. Certifying conductor ampacities and short-circuit current calculations
  4. Interpreting the Code and approving equipment and materials Correct answer.

Explanation

Section 90.4 assigns the AHJ responsibility for interpreting the Code and for approving equipment and materials, including granting special permission for alternate methods where equivalent safety is demonstrated. The AHJ does not perform the designer's work or the installer's calculations.

Question 16General Code Requirements, Definitions, and Administration

A switchboard rated 1200 amperes and 8 ft wide contains overcurrent devices and is installed in a room. What does Section 110.26(C) require for entrance to the working space?

  1. A single entrance of any width is sufficient
  2. One entrance with a minimum clear width of 24 in
  3. Two entrances located at the same end of the equipment
  4. Two entrances, one at each end of the working space Correct answer.

Explanation

Section 110.26(C)(2) requires two entrances to the working space, one at each end, for equipment rated 1200 amperes or more and over 1.8 m (6 ft) wide that contains overcurrent devices, switching devices, or control devices. A single entrance is allowed only under the narrow conditions described in the exceptions.

Question 17General Code Requirements, Definitions, and Administration

Service equipment on a commercial building is field marked with the available fault current. After the utility increases transformer capacity, what does the Code require?

  1. The marking must be updated to show the new value Correct answer.
  2. The marking must be removed until the next inspection
  3. The marking may stand if a note is added to the maintenance log
  4. The marking is required only at the original installation

Explanation

Section 110.24(A) requires service equipment in other than dwelling units to be field marked with the maximum available fault current, and 110.24(B) requires that the marking be updated where the available fault current changes. The marking must be durable and legible so it remains useful to future workers.

Question 18General Code Requirements, Definitions, and Administration

Section 110.10 requires the overcurrent protective devices, total impedance, equipment short-circuit current ratings, and other circuit characteristics to be selected and coordinated so that they will do which of the following?

  1. Limit available fault current to 10,000 amperes
  2. Clear a fault without extensive damage Correct answer.
  3. Prevent the utility from changing transformer size
  4. Eliminate the arc flash hazard at the equipment

Explanation

Section 110.10 requires that the circuit's overcurrent devices, total impedance, equipment short-circuit current ratings, and other characteristics be selected and coordinated so the protective devices will clear a fault without extensive damage to the circuit components. This requirement underlies available fault current and coordination studies.

Question 19General Code Requirements, Definitions, and Administration

A 100-ampere circuit breaker with terminals rated 75°C is used to terminate conductors rated 60°C. Which temperature column must be used to determine the conductor ampacity?

  1. The 90°C column
  2. The 75°C column
  3. The 60°C column Correct answer.
  4. The average of the 60°C and 75°C columns

Explanation

Section 110.14(C) limits conductor ampacity to the lowest temperature rating of any connected termination, conductor, or device. Because the conductor itself is rated 60°C, the 60°C column governs even though the breaker terminals are rated 75°C.

Question 20General Code Requirements, Definitions, and Administration

Listed equipment is installed in a way that conflicts with the instructions included in the listing. What is the Code result?

  1. A Code violation, because listing instructions apply Correct answer.
  2. Acceptable, because the equipment is listed
  3. Acceptable with written manufacturer approval
  4. Acceptable if the AHJ does not inspect the work

Explanation

Section 110.3(B) requires listed or labeled equipment to be installed and used in accordance with any instructions included in the listing or labeling. Installing contrary to those instructions removes the basis for the listing and is a violation regardless of the product's listing mark.

Question 21Wiring Methods, Materials, and Installation Practices

Type NM cable installed through bored holes in wood framing must be secured at intervals not exceeding which maximum distance?

  1. 10 ft
  2. 8 ft
  3. 6 ft
  4. 4½ ft Correct answer.

Explanation

Section 334.30 requires Type NM cable to be secured and supported at intervals not exceeding 1.4 m (4½ ft) and also within 300 mm (12 in) of every box and fitting. Both limits apply; the shorter one governs near boxes.

Question 22Wiring Methods, Materials, and Installation Practices

In a dwelling unit, receptacles along a wall space must be arranged so that no point along the floor line is more than what distance from a receptacle outlet?

  1. 8 ft
  2. 4 ft
  3. 6 ft Correct answer.
  4. 12 ft

Explanation

Section 210.52(A)(1) requires that no point measured horizontally along the floor line of any wall space be more than 1.8 m (6 ft) from a receptacle outlet. Wall spaces 2 ft or wider are included in the measurement.

Question 23Wiring Methods, Materials, and Installation Practices

Where Type NM cable passes through bored holes in wood studs, a listed steel plate is required when the hole is less than what distance from the nearest edge of the framing member?

  1. 1 in
  2. 1½ in
  3. 2 in
  4. 1¼ in Correct answer.

Explanation

Sections 300.4(A)(1) and 334.17 require protection where cable passes through a bored hole less than 32 mm (1¼ in) from the nearest edge of a stud or joist. The plate prevents nails and screws from penetrating the cable.

Question 24Wiring Methods, Materials, and Installation Practices

How many conductor volumes are counted in a box-fill calculation for four 12 AWG equipment grounding conductors entering a box?

  1. Three
  2. Four
  3. One Correct answer.
  4. Two

Explanation

Section 314.16(B)(5) counts all equipment grounding conductors in a box together as a single conductor, sized to the largest grounding conductor present. Four 12 AWG grounds therefore count as one 12 AWG conductor.

Question 25Wiring Methods, Materials, and Installation Practices

What is the minimum depth of working space in front of a 120/240-V panelboard where the voltage to ground does not exceed 150 V and the opposite side of the working space is a wall of insulating material?

  1. 48 in
  2. 30 in
  3. 42 in
  4. 36 in Correct answer.

Explanation

Table 110.26(A)(1), Condition 1 requires 900 mm (3 ft) of depth for equipment operating at 0 to 150 V to ground with no live or grounded parts across the working space. Greater depths apply under Conditions 2 and 3.

Question 26Wiring Methods, Materials, and Installation Practices

Rigid metal conduit installed as a direct-buried raceway in a location not subject to vehicular traffic requires a minimum cover of what depth?

  1. 6 in Correct answer.
  2. 24 in
  3. 12 in
  4. 18 in

Explanation

Table 300.5 lists 150 mm (6 in) of cover for rigid metal conduit in general underground locations. Deeper cover is required under streets, driveways, and parking lots, and for other raceway types.

Question 27Wiring Methods, Materials, and Installation Practices

Type EMT installed in a straight horizontal run must be supported at intervals not exceeding what distance?

  1. 6 ft
  2. 4½ ft
  3. 10 ft Correct answer.
  4. 8 ft

Explanation

Section 358.30(A) requires EMT to be fastened within 900 mm (3 ft) of each box or termination and supported at intervals not exceeding 3 m (10 ft). Supports must be listed for the application.

Question 28Wiring Methods, Materials, and Installation Practices

Which receptacles in a dwelling unit must be listed as tamper resistant?

  1. Only the receptacles installed within 6 ft of the outer edge of a sink
  2. All 125-V, 15- and 20-A receptacles, with limited exceptions Correct answer.
  3. Only 250-V receptacles installed in habitable rooms and within reach of children
  4. Only the receptacles installed in guest rooms of hotels and motels

Explanation

Section 406.12 requires tamper-resistant receptacles for 125-V, 15- and 20-A receptacles in dwelling units, with limited exceptions such as receptacles that are not readily accessible. The requirement is based on voltage and ampere rating, not on room location.

Question 29Wiring Methods, Materials, and Installation Practices

The radius of the inner edge of a bend in Type NM cable must not be less than how many times the diameter of the cable?

  1. 8 times
  2. 6 times
  3. 4 times
  4. 5 times Correct answer.

Explanation

Section 334.24 prohibits bends that damage the cable and sets the minimum bending radius at five times the cable diameter. A tighter bend can distort the conductors and the sheath.

Question 30Wiring Methods, Materials, and Installation Practices

A box contains two 12 AWG ungrounded conductors, two 12 AWG grounded conductors, one 12 AWG equipment grounding conductor, two internal cable clamps, and one duplex receptacle. What minimum box volume is required?

  1. 17.00 in³
  2. 20.25 in³
  3. 15.75 in³
  4. 18.00 in³ Correct answer.

Explanation

Under 314.16(B), the four circuit conductors count as four, the grounding conductors count as one, the clamps count as one, and the single yoke counts as two conductors of the largest size. That is eight volumes at 2.25 in³ each, or 18.0 in³.

Question 31Wiring Methods, Materials, and Installation Practices

When may conductors be pulled into a raceway system?

  1. Before the raceway is complete, if the open ends are capped
  2. After the raceway has been bonded at both ends
  3. Once a partial inspection of the raceway run has been approved
  4. Only after the raceway is complete between boxes and fittings Correct answer.

Explanation

Section 300.18(A) requires raceways to be installed complete between outlet, junction, and control devices before conductors are pulled in. This allows the raceway to be inspected and prevents damage during construction.

Question 32Wiring Methods, Materials, and Installation Practices

Six current-carrying conductors are installed in a single raceway. To what percentage of the Table 310.16 ampacity must each conductor be adjusted?

  1. 50 percent
  2. 80 percent Correct answer.
  3. 70 percent
  4. 75 percent

Explanation

Table 310.15(C)(1) requires an 80 percent adjustment factor for four to six current-carrying conductors in a raceway or cable. The factor decreases as additional conductors are added.

Question 33Wiring Methods, Materials, and Installation Practices

In a single-family dwelling, which of these locations requires ground-fault circuit-interrupter protection for all 125-V, 15- and 20-A receptacles?

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

Explanation

Section 210.8(A)(1) requires GFCI protection for all 125-V, 15- and 20-A receptacles in dwelling-unit bathrooms. Kitchens, garages, outdoors, basements, and other listed areas carry the same requirement.

Question 34Wiring Methods, Materials, and Installation Practices

Which branch circuits in a dwelling unit require arc-fault circuit-interrupter protection?

  1. All 120-V, 15- and 20-A branch circuits supplying outlets in dwelling units Correct answer.
  2. Only 20-A circuits that supply kitchen countertop and bathroom receptacles
  3. Only branch circuits that supply receptacles in bedrooms, closets, and hallways
  4. Only the branch circuits that supply bedroom receptacle outlets

Explanation

Section 210.12(A) requires AFCI protection for all 120-V, single-phase, 15- and 20-A branch circuits supplying outlets and devices in dwelling units, with limited exceptions. The protection is not limited to bedrooms or to one ampere rating.

Question 35Wiring Methods, Materials, and Installation Practices

Receptacles serving a dwelling-unit kitchen countertop must be installed so that no point along the countertop wall line is more than what distance from a receptacle outlet?

  1. 12 in
  2. 24 in Correct answer.
  3. 18 in
  4. 20 in

Explanation

Section 210.52(C)(1) requires countertop receptacle outlets to be spaced so that no point along the wall line is more than 600 mm (24 in) from a receptacle. The receptacles must also be no more than 500 mm (20 in) above the countertop.

Question 36Wiring Methods, Materials, and Installation Practices

Type MC cable must be secured and supported at intervals not exceeding what distance?

  1. 12 ft
  2. 8 ft
  3. 3 ft
  4. 6 ft Correct answer.

Explanation

Section 330.30 requires Type MC cable to be secured and supported at intervals not exceeding 1.8 m (6 ft) and within 300 mm (12 in) of boxes and fittings. The support must be by an approved means.

Question 37Wiring Methods, Materials, and Installation Practices

Type NM cable is permitted to be installed in which of the following?

  1. In a plenum space used to move environmental air
  2. Concealed in a dry wood-frame wall cavity Correct answer.
  3. Inside a raceway installed in a wet location
  4. Directly buried beneath a concrete slab

Explanation

Section 334.10 permits Type NM cable in normally dry locations, including concealed within wood-frame walls. Section 334.12 prohibits its use in wet or damp locations, in plenums, and in masonry or concrete subject to moisture.

Question 38Wiring Methods, Materials, and Installation Practices

The grounded conductor of a branch circuit must be identified by which color?

  1. Green with yellow stripes
  2. Blue or orange
  3. White or gray Correct answer.
  4. Black or red

Explanation

Section 200.6(A) requires the grounded conductor to have a continuous white or gray outer finish, or three continuous white stripes on insulation other than green. This identification must be visible at terminations.

Question 39Wiring Methods, Materials, and Installation Practices

The receptacle outlet required in a dwelling-unit laundry area must be supplied by a branch circuit with a rating of at least what value?

  1. 20 A Correct answer.
  2. 40 A
  3. 30 A
  4. 15 A

Explanation

Section 210.11(C)(2) requires a 20-A laundry branch circuit, and 210.52(F) requires at least one 125-V, 20-A receptacle outlet in the laundry area. That circuit may not supply outlets outside the laundry area.

Question 40Wiring Methods, Materials, and Installation Practices

A 60-A overcurrent device protects a feeder with copper conductors. What is the minimum size copper equipment grounding conductor required?

  1. 6 AWG
  2. 10 AWG Correct answer.
  3. 8 AWG
  4. 14 AWG

Explanation

Table 250.122 requires a 10 AWG copper equipment grounding conductor for a circuit protected at 60 A. The equipment grounding conductor is sized to the rating of the overcurrent device, not to the size of the circuit conductors.

Question 41Wiring Methods, Materials, and Installation Practices

A 12 kW, 240-V single-phase load is located 100 ft from the panelboard. Using K = 12.9, what is the smallest copper conductor that limits voltage drop to 3 percent?

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

Explanation

The load current is 50 A and the permitted drop is 7.2 V. The circular-mil calculation gives 2 x 12.9 x 50 x 100 / 7.2 = 17,917 CM, which exceeds 8 AWG at 16,510 CM, so 6 AWG at 26,240 CM is the smallest compliant size.

Question 42Wiring Methods, Materials, and Installation Practices

A service-entrance conductor is 400 kcmil copper. What is the minimum size copper grounding electrode conductor required by Table 250.66?

  1. 1/0 AWG Correct answer.
  2. 1 AWG
  3. 2/0 AWG
  4. 2 AWG

Explanation

Table 250.66 requires a 1/0 AWG copper grounding electrode conductor for service-entrance conductors larger than 350 kcmil through 600 kcmil. The size is based on the area of the largest service conductor.

Question 43Wiring Methods, Materials, and Installation Practices

A circuit originally wired with 8 AWG copper conductors and a 10 AWG copper equipment grounding conductor was increased to 4 AWG to reduce voltage drop. What minimum size equipment grounding conductor is now required?

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

Explanation

Section 250.122(B) requires the equipment grounding conductor to be increased proportionally when the circuit conductors are increased in size. The 4 AWG phase conductors have about 2.5 times the circular-mil area of 8 AWG, so the 10 AWG grounding conductor must increase to 6 AWG.

Question 44Wiring Methods, Materials, and Installation Practices

Six 8 AWG THHN copper current-carrying conductors are installed in one raceway in a 40 degrees C ambient. What is the ampacity of each conductor?

  1. 36 A
  2. 44 A
  3. 32 A
  4. 40 A Correct answer.

Explanation

Eight AWG THHN in the 90 degrees C column has an ampacity of 55 A. Applying the 0.80 adjustment for four to six conductors and the 0.91 correction for a 40 degrees C ambient gives 55 x 0.80 x 0.91 = 40 A.

Question 45Wiring Methods, Materials, and Installation Practices

What is the maximum number of 12 AWG THHN copper conductors permitted in a 1/2-inch electrical metallic tubing?

  1. 8
  2. 12
  3. 9 Correct answer.
  4. 10

Explanation

For more than two conductors, Chapter 9 Table 1 permits 40 percent fill. A 1/2-inch EMT has 0.304 in² of total area, so 40 percent is 0.122 in²; each 12 AWG THHN conductor occupies 0.0133 in², which allows 9 conductors.

Question 46Wiring Methods, Materials, and Installation Practices

A one-family dwelling is served by a feeder installed as Type UF cable direct-buried beneath the residential driveway. What is the minimum earth cover required over the cable?

  1. 18 in. Correct answer.
  2. 36 in.
  3. 12 in.
  4. 24 in.

Explanation

Table 300.5 sets the minimum cover for direct-buried cables under a driveway, parking lot, or airport apron at 18 in. where the property is a one-family or two-family dwelling. Reduced cover of 12 in. is limited to 120-V, 20-A residential branch circuits that are GFCI protected, which does not apply to a feeder. Where the driveway serves other than a dwelling, the required cover increases to 24 in.

Question 47Wiring Methods, Materials, and Installation Practices

What is the minimum length of free conductor that must be left at each outlet, junction, and switch box for splices or terminations?

  1. 4 in.
  2. 6 in. Correct answer.
  3. 18 in.
  4. 9 in.

Explanation

Section 300.14 requires at least 150 mm (6 in.) of free conductor at each box, measured from the point where the conductor emerges from its raceway or cable sheath. In addition, at least 75 mm (3 in.) of that conductor must extend outside the box opening. Longer lengths are permitted but are not the minimum required.

Question 48Wiring Methods, Materials, and Installation Practices

In a run of electrical metallic tubing between two junction boxes, what is the maximum number of 90-degree (quarter) bends permitted without a pull point?

  1. Three
  2. Two
  3. Six
  4. Four Correct answer.

Explanation

Section 358.26 limits a run between pull points to the equivalent of four quarter bends, which totals 360 degrees, and offsets and other bends count toward that total. The limit exists because additional bends make pulling difficult and can abrade conductor insulation. A pull point must be added whenever the total would exceed that amount.

Question 49Wiring Methods, Materials, and Installation Practices

Type NM cable is run through a bored hole in a wood stud, and the nearest edge of the hole is 1 in. from the edge of the stud. What protection is required at this location?

  1. Seal the hole with fire-rated caulk
  2. Install a steel nail plate over the cable Correct answer.
  3. Install an insulating bushing in the hole
  4. Wrap the cable with two layers of electrical tape

Explanation

Where cable passes through a framing member at a distance less than 1-1/4 in. from the nearest edge, Section 300.4 requires a steel plate at least 1/16 in. thick to shield the cable from nails and screws. Because the hole here is only 1 in. from the edge, protection is mandatory. Bored holes at 1-1/4 in. or more from the edge need no plate.

Question 50Wiring Methods, Materials, and Installation Practices

A straight 100 ft run of rigid PVC conduit is installed where the conduit temperature will range from 40 degrees F to 100 degrees F. Using an expansion coefficient of 3.4 x 10^-5 in./in./degrees F, what total length change must the expansion fittings accommodate?

  1. 1.2 in.
  2. 4.9 in.
  3. 2.4 in. Correct answer.
  4. 0.24 in.

Explanation

Length change equals length times coefficient times temperature difference: 1200 in. x 3.4 x 10^-5 x 60 degrees F, which is about 2.45 in., rounded to 2.4 in. Rigid PVC expands significantly with temperature, so a straight exposed run needs expansion fittings able to absorb that travel. The temperature swing here is 60 degrees F, not the 40 degrees F or 100 degrees F endpoints themselves.