Chapter 1: Definitions
Define Accessible (as applied to equipment)
Capable of being reached for operation, renewal, and inspection
A premises wiring system supplied by a grounded ac electrical service, shall have a grounding electrode conductor connected _____.
To the grounded service conductor
The grounded conductor of an ac service is connected to a grounding electrode system to limit the voltage to ground imposed on the system by lightning and line surges. It also stabilizes the voltage to ground during normal operation, including short circuits. Refer to Section 250.24(A).
The maximum unsupported and unsecured length of Type MC cable used to supply a luminaire in an accessible ceiling is permitted to be not more than _____ in length
6 Ft
When calculating the service-entrance conductors for a farm service, the second largest load of the total load, shall be calculated at _____.
75%
When calculating the total load for a farm service, the demand for the second largest load is 75%, because it is assumed all the loads will not be used continuously for an indefinite period of time. Refer to Table 220.103.
Define Bulkhead
A vertical structural wall, usually of stone, timber, metal, concrete, or synthetic material, constructed along, and generally parallel to, the shoreline to retain earth as an extension of the upland, and often to provide suitable water depth at the waterside face.
What is the maximum voltage permitted between branch-circuit conductors supplying luminaires in a residence or guest rooms of hotels and motels?
120 Volts
The requirement in Section 210.6(A)(1), limiting the voltage of luminaires to 120 volts, is intended to reduce the exposure of residents in dwellings and similar occupancies to electric shock hazards when using or servicing permanently installed luminaires and cord-and-plug connected portable lamps.
Direct-buried cables or conductors located in a trench below two (2) inch thick concrete or equivalent shall have a minimum cover requirement of _____.
18 inches
When a retail furniture store has 80 continuous linear feet of display show window, the NEC mandates at least _____ receptacle outlets be provided within 18 inches of the top of the show window for the show window lighting.
7
To prevent the use of floor receptacles and extension cords, receptacles are required to be installed directly above a show window, within 18 in. of the top, and no point along the top of the window is permitted to be more than 6 feet from a receptacle. Therefore, a receptacle is required for every 12 linear ft. of show window. Refer to Section 210.62. The calculation for 80 continuous feet of show window is as follows: 80 ft. (show window)/12 ft. (per receptacle = 6.7 = 7 receptacles
Define Cable Bundle
A group of cables that are tied together or in contact with one another in a closely packed configuration for at least 1.0 m
Where a grounding ring consist of size 2 AWG bare copper wire encircling a building, buried 36 inches, in direct contact with the earth, what is the minimum length of the wire permitted for the grounding electrode in this ground ring?
20 Ft
To qualify as a grounding electrode, the size 2 AWG bare copper conductor is to be in one continuous 20 ft. length. Refer to Section 250.52(A)(4). This type of grounding method is commonly used in sandy areas, such as West Texas, Eastern New Mexico, Arizona, and Southern California
For one-family dwellings supplied by a single-phase 120/240-volt system the service-entrance conductors are permitted to be sized at not less than _____ of the service demand rating, if no adjustment or correction factors are to be applied.
83%
Determine the maximum number of 125-volt, general-purpose receptacles the NEC permits to be protected by a 20-ampere, 120-volt, single-pole inverse time circuit breaker in a commercial occupancy.
13
Section 220.14(I) requires receptacles on a single strap to be considered a load of 180 VA each. To determine how many receptacles are permitted to be connected to a circuit, first find the VA of the circuit (volts x amperes) and divide the result by 180 VA. Thus, 120 volts x 20 amperes = 2,400 VA (circuit) 2,400 VA (circuit) ÷ 180 VA (one receptacle) = 13 receptacle outlets
Define Electrolyte
The medium that provides the ion transport mechanism between the positive and negative electrodes of a cell.
As a general rule, in the kitchen of a dwelling unit, at least one 15- or 20-ampere, 125-volt, receptacle outlet shall be installed so that no point along the wall line on countertops and work surfaces is more than _____ measured horizontally from a receptacle outlet in that space.
24 Inches
The purpose of Section 210.52(C)(1) is to eliminate the need for the use of extension cords extending from the receptacles supplying portable cooking appliances on the countertop or work surfaces. Most portable cooking appliances are provided with a cord at least 2 feet long or longer. Therefore, an extension cord is not needed when the receptacles are installed within this required horizontal distance. The receptacles are to be spaced no further than 4 feet apart where no point along the wall line is more than 24 in. from a receptacle outlet.
In general, when grounded or ungrounded conductors are installed in parallel, (electrically joined at both ends) the paralleled conductors in each phase shall _____.
I. be the same size in circular mil area
II. have the same insulation type
Both I and II
As required by Section 310.10(G)(2), where connected in parallel, all conductors of the same phase are to be the same size in circular mil area and have the same insulation type. In addition to the requirement of each paralleled phase conductors being the same size and insulation type, the proper grouping of phases in relation to one another can reduce inductive heating and result in a more balanced load between each conductor of a paralleled phase.
A single-phase, 120/240 volt, 18 kW rated home standby generator has a full-load current rating of _____.
75 Amperes
I = power/volts
I = 18 kW x 1,000/240 volts = 18,000/240 = 75 amperes
Define Two-Fer
An assembly containing one male plug and two female cord connectors used to connect two loads to one branch circuit.
Circuit breakers rated _____ or less and 1000 volts or less shall have the ampere rating molded, stamped, etched or similarly marked into their handles or escutcheon areas.
100 Amperes
Section 240.83(B) requires circuit breakers rated 100 amperes or less and 1000 volts or less to have the ampere rating molded, stamped, or marked into their handles or escutcheon areas. This rule aids in identifying the ampere ratings of circuit breakers.
Determine the ampacity of a size 2 THHN copper conductor to be installed in a conduit of more than 2 ft. in length with 3 other current-carrying conductors in an ambient temperature of 115°F.
85 Amperes
Given: All of the following copper conductors are to be installed in an electrical metallic tubing (EMT) ten (10) feet long:
• 24 - size 10 AWG THHW
• 10 - size 10 AWG THHN
• 14 - size 12 AWG THHN
Determine the minimum trade size EMT required.
2 In
As shown, first calculate the total area occupied by the conductors, using Table 5 of Chapter 9:
Size 10 AWG THHW = .0243 sq. in. x 24 = 0.5832 sq. in.
Size 10 AWG THHN = .0211 sq. in. x 10 = 0.2110 sq. in.
Size 12 AWG THHN = .0133 sq. in. x 14 = 0.1865 sq. in.
Total = 0.9807 sq. in.
Next, use Table 4 of Chapter 9 to select the proper trade size EMT permitted to enclose the conductors. Trade size 2 in. EMT with a 40% allowable fill of 1.342 sq. in. should be selected.