Unit 1: Pie Circle Formulas Flashcards
Understanding and applying Ohm’s Law and Watt’s Law using circular formulas to solve electrical calculations involving power, voltage, current, and resistance in accordance with the 2023 NEC®.
Fill in the blank:
Where multiple driven ground rods are installed at an electrical service, they shall be spaced not less than _____ apart.
6 feet
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Where a one-family dwelling has a 200 ampere, 120/240-volt, single phase main service panel and is being supplied with size 2/0 AWG THW copper ungrounded (line) service-entrance conductors in rigid metal conduit (RMC), the minimum required size of the bonding jumper for this service entrance conduit is _____ copper.
4 AWG
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A disconnect switch enclosure installed in a Class II, Division 2, hazardous location in an industrial establishment shall be _____.
dusttight
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The interior of enclosures or raceways installed underground shall be considered to be a _____ location.
wet
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When sizing branch circuit conductors, feeder conductors or serviceentrance conductors and the ambient temperature is other than 30°C (86°F), the correction factor values given in _____ of the NEC are to be applied.
Table 310.15(B)(1)(1)
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The NEC defines a continuous load to be a load where the maximum current on the circuit is expected to continue for at least _____ hours or more.
three
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The Code mandates branch circuit conductors supplying a single motor used in a continuous duty application to have an ampacity of not less than _____ percent of the motor full-load current rating.
4 AWG
Given: You have determined a conductor has a computed ampacity of 75 amperes. What is the maximum standard ampere rating of the overcurrent protection device the NEC permits to protect this circuit when this is not a motor circuit or part of a multioutlet branch circuit supplying more than one receptacle?
80 amperes
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A 208-volt, 3-phase, 50 hp, squirrel-cage, continuous-duty, ac motor has a full-load running current rating of _____.
143 amperes
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For continuous-duty motors, the motor nameplate current rating is used to determine the ____\__ required for the motor.
rating or setting of the motor overload protection
Determine the minimum trade size electrical metallic tubing (EMT) required to enclose eight (8) size 6 AWG copper conductors with THHW insulation, when installed in a 50-foot conduit run.
11⁄4 in
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Where exceptions are not applicable, when a feeder supplies a continuous load of 240 amperes, the overcurrent protection device protecting this feeder circuit shall have a rating of at least _____.
300 amperes
240 amperes x 125% = 300 amperes
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Disregarding exceptions, liquid tight flexible metal conduit (LFMC) shall be securely fastened in place within _____ of each box, cabinet or other conduit termination.
12 inches
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When a pull box or junction box contains conductors of size 4 AWG and larger and a straight pull of the conductors is to be made, the length of the box shall not be less than _____ times the trade diameter of the largest conduit entering the pull box or junction box.
eight
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Conduit nipples not over 24 inches long may be filled to a maximum of _____ of their cross-sectional area.
60 percent
Determine the maximum number of size 14 AWG THHN conductors permitted to be installed in a trade size 3/8 in. flexible metal conduit (FMC) that contains a bare size 14 AWG grounding conductor, when the FMC has external fittings.
four
Which type of conduits does the NEC permit to enclose conductors supplying wet-niche underwater swimming pool luminaires?
schedule 40 rigid polyvinyl chloride conduit (PVC)
True or False:
The Code mandates that electrical equipment shall be installed in a professional and skillful manner.
TRUE
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As a general NEC rule, the dedicated branch circuit supplying the required 125-volt, single-phase, 15- or 20-ampere receptacles in a residential attached garage shall have no other outlets however, an exception to this rule is _____.
readily accessible outdoor receptacles
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In new installations, the minimum clear working space the NEC requires between a 480Y/277-volt, switchboard and a 480-volt motor control center where facing each other is _____.
4 feet
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In the guest rooms of hotels, motels, and sleeping rooms of dormitory units, a minimum of _____ 125-volt, 15- or 20-ampere, general purpose receptacles installed in the room is/are required to be readily accessible.
two
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When branch circuit conductors are installed inside a ballast enclosure of a luminaire and are within three (3) inches of the ballast, the conductors shall have a temperature rating not lower than _____, unless supplying a luminaire marked as suitable for a different insulation temperature.
90 deg. C
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Where raceways contain size 4 AWG or larger insulated conductors and enter a panelboard, switchboard, or cabinet, _____ must be provided.
an identified bushing or threaded hub
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Class _____ locations are those that are hazardous because of the presence of nonmetallic combustible fibers are in the air under normal operating conditions in quantities sufficient to produce explosive mixtures.
III
