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IEC SECOND YEAR FINAL EXAM 2024 | ALL
QUESTIONS AND CORRECT ANSWERS |
ALREADY GRADED A+ | VERIFIED
ANSWERS | LATEST VERSION
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 _____. ------CORRECT ANSWER--------------- 4 The largest trade size Schedule 80 PVC available that can be installed between two big pull boxes is ______. ------CORRECT ANSWER------------- -- 6 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. ------CORRECT ANSWER--------------- 1 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 ------CORRECT ANSWER---------------4 x 2 1/8 square box with a 4.1 cu. in. two-gang plaster ring 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 _______." ------CORRECT ANSWER---------------2 1/ 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 ______. ------CORRECT ANSWER--------------- interlocked Vertically- mounted SPDT swithces shall be ON when in the ______ position.
- i. up
- i. down ------CORRECT ANSWER---------------either i or ii 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 _______. ------CORRECT ANSWER---------------6'-7" 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 ------CORRECT ANSWER------------ ---both i and ii 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. ------ CORRECT ANSWER---------------middle
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. ------CORRECT ANSWER--------------- 30 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. ------CORRECT ANSWER--------------- 6 A unit switch is the ON/OFF switch on an appliance that disconnects all ____ conductors. ------CORRECT ANSWER---------------ungrounded A magnetic field is made up of invisible lines of force called ______ ------ CORRECT ANSWER---------------magnetic flux Where operating in the United States, AC voltage reaches a negative peak _____ times during one second. ------CORRECT ANSWER--------------- 60 Anex _____ in the NEC contains examples of load calculations for dwellings. ------CORRECT ANSWER---------------D 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 ------CORRECT ANSWER--------- ------all of these
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 ------CORRECT ANSWER------- --------the bare aluminum wire twisted with triplex Which of the following statements is TRUE for an individual (or dedicated) branch circuit that is run in a conduit with other circuits? ------CORRECT ANSWER---------------it can share a neutral with another circuit 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 ------CORRECT ANSWER---------------all of these The NEC permits the insulation for an ungrounded conductor to be _____ in color.
- orange
- black
- brown
- yellow ------CORRECT ANSWER---------------any of these 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? ------CORRECT ANSWER---------------a townhome
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 ------CORRECT ANSWER---------------ii or iii only Which of the following is a type of circuit condition? i.short circuit ii. overload ------CORRECT ANSWER---------------i and ii 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. ------ CORRECT ANSWER---------------The load will operate normally and the breaker will not trip 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. ------ CORRECT ANSWER---------------i or ii only 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 _______. ------ CORRECT ANSWER--------------- 2 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. ------CORRECT ANSWER---------------have no effect on
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? ------CORRECT ANSWER---------------10 ft of trade size 1 rigid metal conduit 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 ------CORRECT ANSWER----------- ----i only 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 ------CORRECT ANSWER---------------is 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. ------CORRECT ANSWER---------------farther apart THHN/THWN ______ permitted to be directly buried (not inside conduit) I/IN ------CORRECT ANSWER---------------is not
In a 60 Hz circuit, containing a 12 uf capacitor, the capacitive reactance is ____ ohms. ------CORRECT ANSWER---------------221. In a circuit with 25 ohms resistance and 50 ohms capacitive reactance, the impedance is ______ ohms. ------CORRECT ANSWER---------------55. 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 _________. ------CORRECT ANSWER---------------20a supply facilties with only one dedicated tent site In an AC circuit the total opposition to current flow is referred to as ______. ------CORRECT ANSWER---------------Impedance (z) True power is measure in ______ ------CORRECT ANSWER--------------- watts _______ surrounds the windings in typical "pole-mounted" transformers. --- ---CORRECT ANSWER---------------oil In reality, transformer efficiency can never be 100% because of ______.
- i.eddy-current losses
- ii. copper losses ------CORRECT ANSWER---------------both i and ii Transformers power ratings can be in ______.
- i. VA
- ii. MVA
- iii. KVA ------CORRECT ANSWER---------------any of these Most commonly, the supply circuit to a transformer is connected to the leads, terminals, or lugs marked as the _______. ------CORRECT ANSWER---------------primary The principle upon which transormers operate is _____. ------CORRECT ANSWER---------------electromagnetic induction A transformer's primary winding and secondary winding are actually connected together. T/F ------CORRECT ANSWER---------------False A load that uses 6.2 KW of power is using _____ watts. -. -.. -.
- .6.2 ------CORRECT ANSWER---------------none of these Generally transformers have an efficiency of more than 90%. T/F ------ CORRECT ANSWER---------------True 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 _______ % ------ CORRECT ANSWER---------------96.
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 ------ CORRECT ANSWER---------------false 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 ------CORRECT ANSWER---------------i or ii 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 ------CORRECT ANSWER---------------7. 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. ------CORRECT ANSWER--------------- 23, Demand Factor is defined as ______ ------CORRECT ANSWER--------------- 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
The ______ rating is the ampere rating or setting of the over current device protecting the conductors. ------CORRECT ANSWER---------------branch circuit General lighting loads for dwelling units are calculated at ______ VA per square foot. ------CORRECT ANSWER--------------- 3 Article 220 required that each single or multiple receptacle on a single strap be calculated at ______ VA ------CORRECT ANSWER--------------- 180 For a single-family dwelling with six appliance loads, demand factors may be applied to ______ of these loads using the standard calculation. ------ CORRECT ANSWER---------------all six Using the standard calculation, the total load for household clothes dryers is computed at ______ VA or the nameplate rating whichever is higher. -----
- CORRECT ANSWER--------------- 5000 Using the standard calculation, the demand load for house hold electric ranges rated in excess of _____ kW is computed per NEC Table 220.55 --- ---CORRECT ANSWER---------------1 3/ For dwellings, heating or A/C loads are calculated at ______ of the nameplate rating and the largest load is used for a standard calculation. ---- --CORRECT ANSWER--------------- 100
