Second Year IEC Final
What minimum size box (or box assembly) is required to contain the following? Exterior MC cable connectors are used on the cables. Two-10/2 with ground MC cables plus One- 12/2 with ground MC cable One- 30 amp 240-volt single receptacle and One- 20 amp 120- volt single receptacle
4 x 2 1/8 square box with a 4.1 cu. in. two-gang plaster ring
A fused switch for a motor is located in the top row of switches in a motor control center. This switch is also disconnecting means for the motor. The maximum height of this switch, from finish floor to the center of the operating handle, is _______ .
6'-7"
Where operating in the United States, AC voltage reaches a negative peak _____ times during one second.
60
The Ampacity of each conductor of a 8/3 AWG multiconductor Type W flexible cable used to supply fastened-in-plalce utilization equipment is ______ amps. See NEC T. 400.4 for available sizes. One of the conductors is an EGC and all conductors have a 75C insulation rating.
65
In an AC circuit the total opposition to current flow is referred to as ______.
Impedance (z)
You need to change from 240 volts to 480 volts to operate a piece of equipment that will require 25 KVA at 480 volts. You must use a transformer that is built specifically for step-up applications. T/F
false
_______ surrounds the windings in typical "pole-mounted" transformers.
oil
The maximum cross-sectional area that can be occupied by conductor in a 40-foot run of conduit is 53% where the conduit contains ______ conductors.
1
Using the standard calculation, the demand load for house hold electric ranges rated in excess of _____ kW is computed per NEC Table 220.55
1 3/4
Your only available grounding electrode is the metal underground water pipe from the water utility. You are required by the NEC to have one other grounding electrode for your service. Which of the following driven electrodes could you use ?
10 ft of trade size 1 rigid metal conduit
For dwellings, heating or A/C loads are calculated at ______ of the nameplate rating and the largest load is used for a standard calculation.
100
40C = ____ F
104
Article 220 required that each single or multiple receptacle on a single strap be calculated at ______ VA
180
You are going to pull in three dedicated (individual) branch circuits into one conduit. Each circuit supplies power to a 120-volt load. The ungrounded conductors will be connected to breakers 2,4 and 6 in a 120/240 volt single phase 3- wire panel board. Per the NEC, the fewest number of neutral conductors you can install for the branch circuit is _______.
2
A switch box will contain the following (one) isolated ground receptacle (one) 12/2 with ground AC cable (BX) with exterior connector The shallowest switch box you can use for this installation is 3"x 2"x _______."
2 1/2
A 175- amp breaker protects a feeder that originates in a 277/480-volt, 3-ph, 4 wire service panel in an office building. Which of the following conductors is the smallest size permitted for the feeder ?
2/0
At a recreational vehicle park, electrical service feeders shall be calculated on basis of not less than 600 volt-amperes per site when equipped with _________.
20a supply facilties with only one dedicated tent site
In a 60 Hz circuit, containing a 12 uf capacitor, the capacitive reactance is ____ ohms.
221.04
A 240-volt safety switch is fed from a 100 KVA transformer that hs Z= 1.8% on its nameplate. If the tqo 1 phase conductors going to the 240-colt switch are "shorted" together , about ______ amps of current will flow through the transformer winding. The fuses in the safety switch should have an AIC rating of at least this many amps.
23,148
General lighting loads for dwelling units are calculated at ______ VA per square foot.
3
A 200-amp breaker protects a feeder that originates in a 120/240 volt, 3 ph, 4 wire service panel in a movie theatre. Which of the following THHN/THWN conductors is the smallest size permitted for the feeder ?
3/0
Trade size 3/4 IMC and RMC use the same fittings. Which of them has the greater wall thickness?
3/4 RMC
The smallest circuit breaker that can be installed in a panel is ____ amp. The circuit supplies power to a 240-volt, single-phase, 5.8 KW, 50-gallon water heater.
30
You are to install IMC between two equipment enclosures. You dont know how many or what size wires will have to be pulled into the conduit. If you install the largest available, this is trade size _____.
4
The maximum length of a flexible cord used to connect data-processing equipment to a branch circuit outlet box is _______.
4.5 meters
Using the standard calculation, the total load for household clothes dryers is computed at ______ VA or the nameplate rating whichever is higher.
5000
In a circuit with 25 ohms resistance and 50 ohms capacitive reactance, the impedance is ______ ohms.
55.9017
A 100-gallon water heater is to be installed to supply hot water to the restrooms in an office building. The water heater is rated for 9.8 KW at 240 volts 1- phase. The minimum size THHN/THWN copper wire that can be installed between the required disconnect switch and the water heater is _____ AWG.
6
A certain piece of equipment is to be connected with SOO flexible cord. The equipment requires 2 ungrounded and 1 grounded conductors. Whati si the smallest AWG size cord that can be used to connect the equipment? All conductors should be counted as a current carrying. The maximum load on any one conductors is 31 amps. The equipment will operate continuously.
6
The largest trade size Schedule 80 PVC available that can be installed between two big pull boxes is ______.
6
The maximum number of 3-pole circuit breakers used as service disconnects permitted in a 3 phase panelboard is ______.
6
A 120/240 volt 1 phase 3 wire panelboard is to be fed from a transformer. The minimum calculated size of the transformer is ______ KVA where the following loads are connected. : Circuit 1 : 120-volt lighting that draws 10 amps Circuit 3 : 17 amps of 120-volt lighting Circuit 5-7 : 16 AMP 240 volt swimming pool motor
7.92
A transformer has a primary rating of 480 volts and supplies 240 volts to a 7.4 KVA load. The circuit that is connected to the primary originates from a 2-pole circuit breaker in a 277/480 volt 3 phase 4 wire panelboard. The current measure in one of the circuit conductors connected tot he breaker is 15.9 amps. The efficiency of this transformer is _______ %
96.96
Anex _____ in the NEC contains examples of load calculations for dwellings.
D
A transformer's primary winding and secondary winding are actually connected together. T/F
False
The unit of measure for capacitance is ______.
Farads
Which of the conversion formulas listed below is correct? Peak = RMS x 1.414 Peak= RMS/1.414
Peak= RMS x 1.414
Which of the conversion formulas listed below is correct? RMS= Peak x .707 RMS= Peak x 1.414
RMS= Peak x .707
A 20-amp multiwire branch circuit is connected to breakers 1 and 3 in a 120/208 volt 3 phase 4 wire panelboard. _____ if the "hot" from breaker 3 and the neutral are connected to a 2000-watt lighting fixture load.
The load will operate normally and the breaker will not trip
Demand Factor is defined as ______
The ratio of the maximum demand of a system, or part of a system, to the total connected load of a system or the part of the system under consideration
Generally transformers have an efficiency of more than 90%. T/F
True
The "J" designation in any of the "S-type" flexible cords designates _____.
a junior size
Which of the following locations requires that a three-way switch be installed at the lower landing and another three-way switch be installed at the upper landing to control the stair way lighting between the 1st and 2nd floors?
a townhome
Equipment designed to open circuits under ____ shall have an interrupting rating not less than the nominal circuit voltage and the current that is available at the line side of the equipment. - short circuit -overload -ground fault
all of these
Which of the following are characteristics of THHN/THWN insulation? - heat-resistant - a nylon outer covering or some equivalent - flame retardant -moisture-resistant
all of these
Which of the installations listed below would be a wet location? -a receptacle installed on the exterior wall of a building - a run of PVC conduit installed on a fishing pier -a luminaire installed on a parking lot pole
all of these
For a single-family dwelling with six appliance loads, demand factors may be applied to ______ of these loads using the standard calculation.
all six
The NEC permits the insulation for an ungrounded conductor to be _____ in color. - orange -black -brown -yellow
any of these
Transformers power ratings can be in ______. -i. VA -ii. MVA -iii. KVA
any of these
An electric-discharge luminaire utilizes a ____ for the operation of the lamp.
ballast
If a common-trip 2-pole breaker is used for a single phase, 208-circuit, ______. -i. both "hots" will open when a short circuit or ground fault occurs -ii. both "hots" can be manually opened
both i and ii
In reality, transformer efficiency can never be 100% because of ______. -i.eddy-current losses -ii. copper losses
both i and ii
The ______ rating is the ampere rating or setting of the over current device protecting the conductors.
branch circuit
Vertically- mounted SPDT swithces shall be ON when in the ______ position. -i. up -i. down
either i or ii
The principle upon which transormers operate is _____.
electromagnetic induction
In vertical conduit runs, such as up through a high-rise building, conductors made of aluminum have support requirements that are _____ than for copper conductors.
farther apart
In a run of conduit, when couplings and connectors are loose this will ____ the amount of time required for a circuit breaker to open when an overload occurs.
have no effect on
A .25KVA transformer has a nameplate rating of 240/480 primary volts 120/240 secondary volts. IF rated voltage is applied to the primary the secondary voltage will be _____ than the nameplate secondary voltage because these small transformers have compensation built into their secondaries. Higher/lower
higher
Which of the following is a type of circuit condition? i.short circuit ii. overload
i and ii
The feeder neutral load is the maximum unbalance between ______. -i. any one of the ungrounded conductors and the grounded conductor -ii. any two of the ungrounded conductors.
i only
Your only available grounding electroe is the metal underground water pipe from the water utility. You are required by the NEC to have one other grounding electrode for your service. You could use which of the following driven electrodes? -i. 10 ft trade size 1 rigid metal conduit -ii. 8' by 1/2 inch copper-clad ground rod
i only
A square D transformer with a nameplate rating of 240/480- V primary and 120/240 volt secondary can be connected to a 2-pole breaker in a _______ panelboard and deliver nameplate-rated voltage to a load. -i. 120/240 volt 3 phase 4 wire -ii. 277/480 V 3 phase 4 wire
i or ii
When ____ touch together this is a short circuit. -i. two ungrounded circuit conductors - ii.an ungrounded and a grounded circuit conductor - iii. an ungrounded circuit conductor and the metal conduit.
i or ii only
When a transformer is loaded beyond its rating the effects in the transformer are ______ -i. excessive temperature -ii. deterioration of insulation -iii. coil failure
i, ii and iii
THHN/THWN ______ permitted to be directly buried (not inside conduit) I/IN
is not
Where a 120/240 volt, 1 phase, 3 wire multiwire branch circuit is connected to a "split-wired" duplex receptacle in a barber shop, the branch-circuit OCPD/disconnect is permitted to be ______ i. two single-pole circuit breakers without handle ties ii. two single-pole circuit breakers with identified handle ties iii. a 2-pole circuit breaker
ii or iii only
When a resistive AC circuit also contains inductance and/or capacitance, the total opposition to current flow is called ______.
impedance
______ in utility transmission lines reduces the power losses in the transmission conductors.
increasing the voltage
When spray application equipment cannot be operated unless the exhaust ventilation system is operating and functioning properly and spray application is automatically stopped if the exhaust ventilation system fails the system is said to be ______.
interlocked
Twenty-five feet of bare 4 AWG copper that is laid in the grade beam within a poured building slab ______ permitted to be used as a grounding electrode for a separately derived system or service. I/IN
is
For the purpose of determining the number of current-carrying conductors in a cable or conduit, the neutral _____ counted when the branch circuit is 120/240-volt, 1 phase, 3 wire connected to a 120/240-volt, 3 phase delta, 4 wire panelboard. Each of the two circuits carries 16 amps and serves resistive (linear) loads.
is not
Dry-type distribution transformers are equipped with _____ to reduce mechanical noise due to vibration.
isolation pads
Which of the following statements is TRUE for an individual (or dedicated) branch circuit that is run in a conduit with other circuits?
it can share a neutral with another circuit
______ shall not support luminairs weighing over 6 lb.
lampholder
A magnetic field is made up of invisible lines of force called ______
magnetic flux
In a 3 phase panelboard that has vertical busbars that are stacked back-to-front, the B phase feeder conductor is connected to the ___ busbar.
middle
A PAR lampholder is installed in a 1-gang weatherproof "bell" box. This box is permitted to be supported by RMC and threadless connectors where ______. -i. no more than 18" of RMC is stubbed out of the ground and enters the box -ii. at least two RMCs are stubbed out of the ground into the bottom of the box
neither i or ii
A load that uses 6.2 KW of power is using _____ watts. -.62 -. .062 -.620 -.6.2
none of these
Most commonly, the supply circuit to a transformer is connected to the leads, terminals, or lugs marked as the _______.
primary
Temperature _____ is the difference in temperature between the transformer windings and the ambient temperature surrounding the transformer.
rise
Which of the following is an example of a bare conductor? - a 12 awg THHN copper wire - the bare ground wire contained within romex (NM cable) sheathing -the bare aluminum wire twisted with triplex
the bare aluminum wire twisted with triplex
A unit switch is the ON/OFF switch on an appliance that disconnects all ____ conductors.
ungrounded
True power is measure in ______
watts
