HW week 2
What is magnetically operated machine that can change values of voltage, current, and impedance without changing frequency?
Transformer
Because not all features of construction can be seen in plan views and elevations from the outside of a building, many construction drawings are _____ views.
section
How many transformers are needed to make an open-delta connection?
2
The total volume occupied by two internal cable clamps, six #12 AWG conductors, and a single-pole switch is _____ cu. in.
20.25
A three-phase transformer bank has the secondary connected in a wye configuration. The center tap is used as a neutral conductor. If the voltage across any phase conductor and neutral is 120 V, how much voltage would be applied to a three-phase load connected to the secondary of this transformer bank?
208
In noncombustible walls or ceilings, the front edge of a box, plaster ring, extension ring, or listed extender employing a flush-type cover, shall be set back not more than _____ " from the finished surface.
1/4
NEC Article 312: Surface-type cabinets, cutout boxes, and meter socket enclosures in damp or wet locations shall be mounted so there is at least _____in. airspace between the enclosure and the wall or supporting surface.
1/4
Article 410 In clothes closets, recessed incandescent or LED luminaires with a completely enclosed light source can be installed in the wall or the ceiling, provided there is a minimum clearance of ______ in. between the luminaire and the nearest point of storage space.
12
If a single-phase load is connected across the two line conductors and neutral of a three-phase transformer and one has a current of 80 A and the other line has a current of 68 A, how much current is flowing in the neutral conductor?
12
Nonmetallic-sheathed cable must be secured within _____ inches from a two-gang plastic device box mounted in a stud wall.
12
Type UF cable, buried underground, fed from a 15-ampere, ground-fault circuit interrupter at a one-family dwelling must have a minimum cover of _____ inches.
12
A three-phase transformer connection has a delta-connected primary and a wye-connected secondary. The center tap of the wye is used as a neutral conductor. If the line-to-line voltage is 480 V, what is the voltage between any one phase conductor and the neutral conductor?
277
A transformer has a turns ratio of 1:6. The primary current is 18 A. What is the secondary current?
3
Article 408 Conduits and raceways, including end fittings, shall not rise more than _____ in. above the bottom of a switchboard enclosure.
3
Article 410 Branch-circuit conductors within _____ in. of a ballast shall have an insulation temperature rating not lower than 90°C.
3
In an isometric projection, the lines are drawn out at which angle?
30
Article 422 An in-sink waste disposer can be cord-and-plug connected, but the cord shall not be less than 18" or more than _____in.
36
NEC Article 344: A run of RMC shall not contain more than the equivalent of _____ quarter bend(s) between pull points such as conduit bodies and boxes.
4
A switch rated for 20 amps will be installed in a device box beside a switch rated for 15 amps. Two 12 AWG THHN copper conductors will be terminated onto the switch rated 20 amps and two 14 AWG THHN copper conductors will be terminated onto the switch rated 15 amps. The required volume allowance for the switch rated 20 amps is _____ cu. in. and the required volume allowance for the switch rated 15 amps is _____ cu. in.
4.50 and 4.00
Oblique projection projects the front of an object out at which angle?
45
A transformer has a primary voltage of 240 V and a secondary voltage of 48 V. What is the turns ratio of this transformer?
5:1
How many #14 AWG THW conductors are permitted in a 3" x 2" x 2-1/2" device box?
6
Type MC cable shall be supported and secured by staples, cable ties, straps, or other approved means at intervals not exceeding _____ feet.
6
A 4-11/6" square box that is 2-1/8" deep already contains two receptacles, two internal cable clamps, four 12AWG THHN copper conductors (two black, two white), two grounding conductors, three wire nuts, two pigtails, and one equipment bonding jumper. (A flat plaster ring was used to secure the receptacles to the box.) How many more 12 AWG THHN copper conductors can be added to this box?
8
Where nonmetallic-sheathed cable is run at angles with joists in unfinished basements, it shall be permissible to secure cables not smaller than three _____ AWG conductors directly to the lower edges of the joists.
8
What are the common efficiencies for transformers?
90% to 99%
What transformer has only one winding used for both the primary and secondary?
Autotransformer
Article 408 Panelboards supplied by a three-phase, 4-wire, delta-connected system shall have the phase with the higher voltage-to-ground (high leg) connected to the _____ phase.
B
How does the NEC specify that the high leg of a four-wire delta connection be marked?
By an orange wire or tape.
_____ are drawings that show height.
Elevations
The length of the lines in the projection are doubled to make the shape more realistic? T or F
F
What type of transformer that has its primary and secondary windings electrically and mechanically separated from each other?
Isolation transformer
Isometric drawings are easier to read when you color in the:
Parallel Faces
What transformer has a higher secondary voltage than primary voltage?
Step-up transformer
A section view shows what would be exposed if a cut were made through object. T or F
T
Article 404 As a general rule, the grounded circuit conductor for the controlled lighting circuit shall be installed at the location where switches control lighting loads that are supplied by a grounded general-purpose branch circuit serving bathrooms, hallways, stairways, and habitable rooms occupiable spaces as defined in the applicable building code. T or F
T
Article 410.130 When connected to multi-wire branch circuits, the disconnecting means shall simultaneously break all the supply conductors to the ballast, including the grounded conductor. T or F
T
Article 400 The allowable ampacity of flexible cables is found in _____.
Tables 400.5(A)(1) and (2)
Orthographic projections may include:
Top view, front view, and side view
NEC Article 330: Type MC cable shall be listed and fittings used for connecting Type MC cable to boxes, cabinets or other equipment shall ______.
be listed and identified for such use
NEC Article 342: IMC shall be secured _____.
by fastening within 3' of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination within 5' of a box or termination fitting when structural members do not readily permit the raceway to be secured within 3' of the termination except when the IMC is within 3' of the service head for an above-the-roof termination of a mast
Type MC cable can be unsupported where the cable is _____.
fished between concealed access points in finished buildings or structures and support is impracticable, not more than 6 ft. from the last point of support within an accessible ceiling for the connection of luminaires or other electrical equipment
Article 422 Receptacles for built-in dishwashers and trash compactors shall be located to protect against physical damage to the _____.
flexible cord
Article 430.6(A)(1) The motor _____ currents listed in Tables 430.247 through 430.250 shall be used to determine the ampacity of motor circuit conductors and short-circuit and ground-fault protection devices.
full-load
NEC Article 300: All conductors of the same circuit shall be _____, unless otherwise specifically permitted in the Code.
in the same raceway or cable,in the same trench
What type of pictorial drawing is easiest to draw on the job site?
isometric
NEC Article 310: Parallel conductors shall have the same _____.
length material size in circular mil area
NEC Article 300: Where type NM cables pass through cut or drilled slots or holes in metal members, the cable shall be protected by _____ which are installed in the opening rior to the installation of the cable and which securely cover all metal edges.
listed bushings, listed grommets
NEC Article 386: The maximum number of conductors permitted in any surface metal raceway shall be ______.
not greater than the number for which it was designed
What type of drawing is used for working drawings?
orthographic
NEC Article 392: A cable tray is a unit or assembly of units or sections and associated fittings forming a _____ system used to securely fasten or support cables and raceways.
structural
NEC Article 358: EMT couplings and connectors shall be made up _____.
tight
