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IEC year 2 final EXAM 2025 AND
PRACTICE QUESTIONS |ACCURATE
ANSWERS| VERIFIED FOR GUARANTEED
PASS |GRADED A |NEW VERSION
1. What is the minimum size THHN/THWN wire permitted to serve a load that will draw 47 amps (non- continuous)? The OCPD is a 75°C rated circuit breaker. A. 12 AWG B. 10 AWG C. 8 AWG D. 6 AWG ✅ Correct Answer: C. 8 AWG Rationale: According to NEC Table 310.16, at 75°C, 8 AWG copper wire is rated for 50 amps, which safely covers the 47-amp load. 2. The smallest wire that can be installed to serve a load with a 127-amp nameplate rating (75°C terminals) is: A. 1 AWG B. 1/0 AWG C. 2/0 AWG D. None of these ✅ Correct Answer: D. None of these Rationale: At 75°C, even 1/0 AWG is rated only for 150 amps. NEC 310.16 does not have an exact match, and conditions (like continuous load or adjustment factors) may require larger wire than listed options. 3. Does the NEC® permit circuits from panels to enter the same pull box shown in Figure 207.8? A. No B. Yes C. Only if under 100 amps D. Only if the panels are on the same phase ✅ Correct Answer: B. Yes Rationale: NEC permits multiple circuits to enter a pull box if space, routing, and fill requirements are met.
4. According to Figure 207.8, conductors from Conduit X can occupy the junction box with conductors from Conduit Z. A. True B. False ✅ Correct Answer: A. True Rationale: If box fill and conductor grouping requirements are satisfied, this is permitted. 5. A steel plate is required to protect which raceways when a 1¼" clearance from wood framing edges can't be maintained? A. I only (EMT) B. II only (PVC) C. I and III only D. Neither I, II, nor III ✅ Correct Answer: D. Neither I, II, nor III Rationale: NEC 300.4(A) requires protection for cables, not conduit, when within 1¼" of wood framing. 6. Where bushings are required, which conduit(s) in Figure 207.10 must have bushings? I. Conduit X (4 AWG) II. Conduit Y (2/0 AWG) III. Conduit Z (1 AWG) A. II only B. I & III only C. I, II, & III D. None ✅ Correct Answer: C. I, II, & III Rationale: NEC 300.4(F) requires bushings for all conductors 4 AWG and larger entering a box. 7. What is the maximum size branch-circuit OCPD permitted for 4 AWG THHN/THWN wire with a non- continuous 83-amp load? A. 70A B. 80A C. 85A D. 90A ✅ Correct Answer: D. 90A Rationale: 4 AWG THHN/THWN at 75°C is rated for 85 amps, but for non-continuous loads, next standard OCPD size (90A) is acceptable. 8. In an AC circuit containing only inductance or capacitance, the opposition to current flow is called: A. Resistance
13. In Figure 205.5, smallest MBJ for panel with three 3/0 AWG ungrounded conductors and one 3/ grounded conductor: A. 6 AWG B. 4 AWG C. 2 AWG D. 1 AWG ✅ Correct Answer: B. 4 AWG Rationale: NEC Table 250.102(C)(1) again specifies 4 AWG copper for MBJ in this situation. 14. Smallest permitted secondary circuit conductors for 32.286 KVA, 240V, 3Ø, non-continuous load: A. 6 AWG B. 4 AWG C. 2 AWG D. 1 AWG ✅ Correct Answer: B. 4 AWG Rationale: 32.286 KVA / (1.732 × 240) ≈ 77.6A; 4 AWG @ 75°C = 85A. 15. Smallest secondary conductors for a 69 KW, 240V, 3Ø transformer: A. 1 AWG B. 2/0 AWG C. 3/0 AWG D. 4 AWG ✅ Correct Answer: B. 2/0 AWG Rationale: 69,000 W / (1.732 × 240) ≈ 166A; 2/0 copper @ 75°C = 175A. 16. Primary current of 112.5 KVA transformer, 480V delta primary, 240V delta secondary, 100A secondary load: A. 65A B. 29A C. 56A D. 41A ✅ Correct Answer: B. 29A Rationale: Power in = Power out → I_primary = (240×100)/(480×√3) ≈ 29A. 17. Code reference requiring secure fastening of equipment: A. 110. B. 110.13(A) C. 240.4(B) D. 250.
✅ Correct Answer: B. 110.13(A) Rationale: NEC 110.13(A) mandates that equipment be firmly secured to its mounting surface.
18. If terminals or lugs are marked with a torque specification, the NEC® requires: A. Use of lock washers B. Hand tightening only C. Torque values must be applied D. Re-torque every 6 months ✅ Correct Answer: C. Torque values must be applied Rationale: NEC 110.14(D) requires that manufacturer-specified torque values be applied to ensure safe and reliable electrical connections. 19. NEC® 110.22 permits a cord and plug for an air compressor to act as a disconnect if: A. It is labeled as such B. It has a switch lock C. Its purpose is obvious D. It is fused ✅ Correct Answer: C. Its purpose is obvious Rationale: NEC 110.22 allows the plug to serve as a disconnect if its function is evident and labeling is not necessary. 20. What is the minimum working clearance at Point X for a 277/480V, 3Ø, 4W panel? A. 3 feet B. 3½ feet C. 4 feet D. 5 feet ✅ Correct Answer: B. 3½ feet Rationale: NEC Table 110.26(A)(1) requires 3½ feet clearance for 277/480V systems with likely grounded equipment on opposite walls. 21. A ¾-inch PVC conduit buried under a future 6" concrete driveway must be at least ___ inches below grade: A. 12 inches B. 18 inches C. 6 inches D. 24 inches ✅ Correct Answer: C. 6 inches Rationale: NEC Table 300.5 requires a 6-inch burial depth under concrete for GFCI-protected residential branch circuits.
✅ Correct Answer: D. Any of these Rationale: Long exhaust runs increase back pressure, which may require various modifications.
27. Which figures in 210.1 fail to comply with NEC 240.22(1)? A. I only B. II only C. I & III only D. II & III only ✅ Correct Answer: C. I & III only Rationale: These figures presumably show OCPD located in inappropriate or non-accessible areas. 28. For a 3Ø, 4-wire 120/208V optional standby generator with neutral bonded and ground rod installed, the transfer switch must have: A. 2 poles B. 3 poles C. 4 poles D. 1 pole ✅ Correct Answer: C. 4 poles Rationale: NEC requires switching the grounded (neutral) conductor to prevent parallel paths. 29. NEC section covering generator overcurrent protection is: A. 240. B. 445. C. 300. D. 430. ✅ Correct Answer: B. 445. Rationale: Generator protection is covered under NEC Article 445, specifically 445.12. 30. Transfer equipment for emergency systems must prevent interconnection of: A. Ground and neutral B. Normal and emergency power C. Indoor and outdoor conductors D. 50 and 60 Hz systems ✅ Correct Answer: B. Normal and emergency power Rationale: NEC requires transfer switches to prevent backfeeding or parallel energizing of sources. 31. ___ power is returned to the source and not consumed. A. Apparent
B. True C. Reactive D. Effective ✅ Correct Answer: C. Reactive Rationale: Reactive power flows into and out of reactive components without doing useful work.
32. Apparent power is measured in: A. Watts B. Volt-amps C. VARs D. Kilowatt-hours ✅ Correct Answer: B. Volt-amps Rationale: Apparent power (total power) in an AC system is measured in volt-amps (VA). 33. True power is measured in: A. VARs B. VA C. Watts D. Ohms ✅ Correct Answer: C. Watts Rationale: True power represents actual work done and is measured in watts. 34. Reactive power is measured in: A. Volt-amps B. Watts C. Ohms D. Volt-amps reactive ✅ Correct Answer: D. Volt-amps reactive Rationale: Reactive power is measured in VAR (volt-amps reactive), representing non-working power. 35. An AC circuit with only resistive loads has current and voltage: A. Out of phase B. In phase C. Lagging D. Leading ✅ Correct Answer: B. In phase Rationale: In purely resistive circuits, voltage and current rise and fall together.
41. In generator exhaust systems, excessive horizontal or vertical piping can cause: A. Reduced voltage B. Overcurrent C. Increased back pressure D. Faulty grounding ✅ Correct Answer: C. Increased back pressure Rationale: Long piping increases exhaust resistance, leading to back pressure that can harm engine performance. 42. Transfer switches for emergency systems must be designed to avoid the interconnection of: A. Airflow ducts B. Loads C. Normal and emergency sources D. Overcurrent devices ✅ Correct Answer: C. Normal and emergency sources Rationale: NEC requires that normal and emergency sources never be connected simultaneously to avoid dangerous backfeeding. 43. Reactive power is defined as: A. Power that performs work B. Power that dissipates as heat C. Power that flows to and from inductors/capacitors D. Power that causes overvoltage ✅ Correct Answer: C. Power that flows to and from inductors/capacitors Rationale: Reactive power doesn't perform useful work but is necessary for voltage control in AC systems. A single-phase transformer requires 32 amps at 480 volts on the primary to deliver 120-volt power to a 14.6 kW load. The efficiency of this transformer is ___ %.
- Ans - 95 Heaters are installed in motor starters to protect ___. I. the motor against overload II. the branch circuit conductors against overload III. the motor against short circuits and ground faults
Underground service laterals that are installed as direct buried cable and covered with 42 inches of dirt shall also have a warning ribbon installed at least ___ inches above the cable. - Ans - 12 What maximum size inverse time circuit breaker is permitted for a single-phase, 7.5 hp motor operating at 208 volts?
- Ans - 110 The service panel feeds the subpanel with two parallel conduits from a 2P, 225-A breaker. There are two "hots" and one neutral in each conduit. AØ loads in the subpanel are pulling 210 amps and BØ loads in the subpanel are pulling 170 amps. Refer to the illustration and the information shown above in Figure 204.1. The AØ conductor in each conduit should be carrying ___ amps of current.
- Ans - 105 Refer to the motor nameplate shown in Figure 230.115. This motor should draw ___ amps when fully loaded and operated at rated voltage from a 1-pole breaker in a 120/240-volt, 1Ø, 3-wire panelboard. - Ans - 30. Refer to the motor nameplate shown in Figure 230.115. A NEMA starter will be used for this motor. The fewest number of heaters that can be installed in the starter per the NEC ® is ___. The motor circuit is supplied from a 2-pole breaker in a 120/240-volt, 3Ø, 4-W panel. - Ans - 1 Torque motors and AC adjustable motors make up about 10% of all large motor applications. Of the remaining 90%, most are ____. - Ans - squirrel-cage induction FLC (full load current) and FLA (full load amps) are the same thing. - Ans - True When replacing a defective motor, a replacement must have the same frame size. - Ans - True
(standard size General Duty) that can be installed for this motor is a ___ A. - Ans - 60 Refer to the information shown in Figure 230.231. To be able to contain time-delay fuses, the smallest, Square D, heavy duty safety switch has a ___ amp rating. - Ans - 200 When a 3Ø, 4-W supply system delivers 120/208 volts, the system is ___ connected. - Ans - wye When a 3Ø, 4-W supply system delivers 120/240 volts, the system is ___ connected. - Ans - delta When a 3Ø, 3-W supply system delivers 480 volts, the system is ___ connected. - Ans - delta If three single-phase, 37.5 KVA transformers are connected together to form a three-phase delta bank, what will be the total KVA rating? - Ans - 112 and 1/ Refer to the information shown in Figure 234.151. When the tap for Motor 3 terminates in a safety switch, the maximum permitted size for DETD fuses in this switch would be _____ A. - Ans - 15 Refer to the information shown in Figure 234.151. When the tap for Motor 1 terminates in a breaker enclosure, the maximum permitted size for an ITCB in this enclosure would be ____ A. - Ans - 70 Refer to the information shown in Figure 234.151. When th etap for Motor 3 terminates in a breaker enclosure, the maximum permitted size for an ITCB in this enclose would be ____ A. - Ans - none of these Voltage Drop Scenario # The distance between the panel and a load is 150 feet. The circuit to the load consists of two 12 AWG solid copper coated conductors that are connected to a 1-pole breaker in a 277/480-volt, 3Ø, 4-wire panel and the neutral bar. The load draws 9.8 amps. Refer to Voltage Drop Scenario #3. If the voltage drop is to be limited to 2.2%, this is ___ volts. - Ans -
Refer to Figure 221.404. The voltage applied to Heating Element B is ___ volts. - Ans - 138.
Refer to the nameplate and heater selection table, shown above in Figure 230.122. For a correctly sized starter, the heater catalog number for the heaters is ___. This motor is supplied power from a 120/240volt, 3-phase, 4-wire panelboard. - Ans - B Refer to the nameplate shown in Figure 230.122. The branch circuit for the motor is supplied from a 240/120-volt, 3Ø, 4-wire panelboard. What is the minimum size (3 wire + ground) SO cord that could be used as a flexible connection for the motor? - Ans - 8 Refer to the nameplate shown in Figure 230.122. This motor should draw ___ amps at rated voltage when connected to Circuit 4- 6 - 8 that is fed from a 3-pole breaker in a 120/240-volt, 3Ø, 4-wire panelboard. - Ans - 18. Two lighting circuits are supplied from a multiwire branch circuit that originates in a 120/240 volt, 1Ø, 3wire panelboard. Two, 20 Amp, 1-pole breakers are installed in spaces 22 & 24 for the multiwire circuit. Circuit 22 has 2600 watts of lights connected to it, and Circuit 24 has 2100 watts of lights connected to it. Which of the following should happen to Circuit 22? - Ans - An overload will occur and the breaker will trip. Refer to Figure 221.402. If Ammeter 2 indicates 38.5 amps, the generator is delivering ___ kW of power. - Ans - 16. The service disconnecting means for a 3-phase service is permitted to consist of ___. - Ans - any of the above Nontime-delay fuses are to be installed in a safety switch adjacent to a motor. See Figure 230.225. Fuses with a rating not exceeding ___ A are permitted. - Ans - 100 The classification of a location, where ignitable concentrations of flammable liquid-produced vapors or combustible liquid-produced vapors exist under normal operating conditions, is ___. - Ans - Class I, Division 1 If a 4-wire, wye-connected supply system has a line-to-line voltage of 13.5 kV, what is the line-to-neutral voltage? - Ans - 7,
Stainless steel ground rod electrodes ___. I. shall be at least 5/ 8 inch in diameter II. shall be at least 10 feet in length - Ans - I only AC cable is the wiring method to be used above in Figure 208.3. The length of the AC cable between luminaires is 10 feet. The maximum distance permitted between support #7 and support #8 is ___ feet. - Ans - 4 1/ 2 The depth ( d) of the 24" x 24" box, shown above in Figure 207.13, is 10 inches. Measured from the point in the box where the conductors emerge from the conduit, the minimum length of the conductors is ___ inches. - Ans - 6 Statement(s) ___, shown below, is (are) true. I. efficiency = output power ÷ input power II. output power = input power - losses - Ans - both I & 2 The smallest standard size metal box that can be used for the following is a ___. All connectors are on the exterior. one- 14 - 2 w/ ground NM cable two- 14 AWG conductors to be connected to the NM cable with wire nuts one- 20 amp 240 volt duplex receptacle (single yoke) two- 12 AWG conductors to be connected to the receptacle one- 12 AWG equipment grounding conductor - Ans - 3¾ x 2 x 3½ masonry box The panel, shown above in Figure 207.6, is 120/240-volt, 1Ø, 3-wire. The load has a rating of 32.4 KW at 240 volts. Each ungrounded conductor will carry ___ amps. - Ans - 135 A three-phase, 240-volt feeder is going to supply power to one 5 hp 3Ø motor, three 2 hp 3Ø motors, and two 1 hp 3Ø motors. The minimum size conductors permitted for this feeder are ___ AWG. - Ans - 8 The vertical bathtub zone in which luminaires are not permitted is ___' from the bathtub rim. - Ans - 8
Motor Nameplate Information: 208-230/460-V 3Ø 5 hp Supply: 3-pole breaker in a 120/208-V, 3-ph, 4-W panel Minimum size circuit conductors are ___ AWG. - Ans - 12 Refer to Figure 221.101 (above). Drawing ___ (below) shows the transformer correctly connected. - Ans - C) Where (snap) switches are installed in multigang boxes without permanent barriers (partitions) the maximum voltage between adjacent switches is ___ volts. - Ans - 300 A 3-phase load draws 37.3 amps and is operating at 208 volts. This load is using ___ KVA of power. - Ans -
Three THHN/THWN copper circuit conductors are connected to a 3-pole breaker in a 480/277-volt, 3Ø, 4- wire panelboard. The circuit serves a load that draws 11.9 amps. The distance between the panel and the load is 176 feet. The smallest conductors you can install to the load are ___ AWG. The specifications limit the voltage drop to 2.1%. Use K = 10.86 to solve this problem. - Ans - 14 The smallest copper service-drop conductors that can be installed for a service are ___. - Ans - 8 Refer to Figure 221.201. The transformer bank has a ___-connected primary ("H" leads). - Ans - delta Figure 207. Nameplate Information: Toaster - 9.2 A @ 110 V Television - 450 W @ 130 V Refer to the wiring diagram shown above in Figure 207.3. What will be the voltage applied (or dropped across) the toaster when the neutral is opened? Select the closest answer. - Ans - 58 What is the full load current of a 230v, 3ph, 30HP squirrel cage motor? - Ans - 80 The calculated minimum width (left-to-right) of the pull box shown in Figure 208.53 is ___ inches. Select the larger dimension required: straight pull dimension versus angle pull dimension. - Ans - 37
The transformer shown in Figure 215.51 has two separate secondary windings. The secondary windings are rated 120/240 volts. If the secondary windings are connected to supply power to a 120/240-volt load, the windings would be connected in ___. - Ans - series A three-phase 69 KVA load will be connected to a circuit that is fed from a 3-pole breaker in a 120/240volt 3Ø, 4-wire panel. This load will draw ___ amps of current through each circuit conductor. - Ans - 166 You are to surface mount 128' of EMT on a wall between two boxes as shown above in Figure 208.11. You will use 1-hole straps to securely fasten the EMT to the wall. The minimum number of straps required is ___. - Ans - D Which of the following could be used in a concrete slab? - Ans - any of these ___ is the output of an AC generator measured in cycles per second. - Ans - Frequency When a 3Ø load is drawing 48 amps at 208 volts, this is a ___ load. - Ans - 17.29 KVA A 480-volt motor circuit can be protected with a safety switch that is rated at ___ volts. - Ans - 600 Individual dry-type transformers rated over 112½ kVA shall be enclosed in a fire-resistant room with materials having a ___-hour minimum fire rating. - Ans - 1 350A fuses are used in the safety switch shown in Figure 205.12. The flex to the motor contains three 4/0 AWG conductors. The minimum size of the Equipment Grounding Conductor (EGC) to the motor is ___ AWG. - Ans - 3 The conductor shown at point I in Figure 205.1 is the ___. - Ans - grounding electrode conductor Anex _____ in the NEC contains examples of load calculations for dwellings. - Ans - 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 - Ans - 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 - Ans - 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? - Ans - 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 - Ans - all of these The NEC permits the insulation for an ungrounded conductor to be _____ in color.
- black
- brown
- yellow - Ans - 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? - Ans - a townhome 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? - Ans - 2/
