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IEC 1st year final review TEST
QUESTIONS ALL VERSIONS 2025 |
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1. The fewest number of 120-volt, 20-amp branch circuits required for lighting in bathroom #1 and receptacles in three bathrooms is: A. 0 B. 1 C. 2 ✅ D. 3 Correct Answer: C. 2 Rationale: NEC requires at least one 20-amp circuit for bathroom receptacles, but if multiple bathrooms are served, a separate circuit is typically required for lighting. Therefore, at least two branch circuits are necessary. 2. A vanity fixture with 24 lamps rated at 60 watts each (120V) will draw how many amps? A. 0. B. 10 C. 3 D. 12 ✅ E. 0. Correct Answer: D. 12 Rationale: Total wattage = 24 × 60 = 1440 watts. Current = Power / Voltage = 1440W / 120V = 12 amps. 3. A 120V parallel circuit has 4 identical loads drawing 11.2A total. What is the resistance of each load? A. 6.18 ohms B. 24.73 ohms C. 42.86 ohms ✅ D. 1.48 ohms E. 45 ohms
Correct Answer: C. 42.86 ohms Rationale: Total current = 11.2A, so current per branch = 11.2 / 4 = 2.8A. R = V/I = 120V / 2.8A ≈ 42.86 ohms.
4. What is the minimum depth of a 2-gang masonry box for two receptacles using #12 pigtails and external cable connectors? A. 1 7/8" B. 2 1/8" C. 2 1/2" D. 1 1/2" E. 3 1/2" ✅ Correct Answer: E. 3 1/2" Rationale: NEC box fill calculations and space for two receptacles and #12 wires necessitate a deeper box; 3½ inches ensures sufficient space. 5. Total current drawn by the duct heater on a 208V circuit (Figure 115.317): A. 8.89 A B. 15.42 A C. 12.31 A ✅ D. 16.89 A E. 13.52 A Correct Answer: C. 12.31 A Rationale: Based on wattage and voltage values given in figure, using I = P/V gives 12.31 A as the calculated load. 6. Copper conductor with 0.778 ohms/1000 ft, 500 ft round-trip, 42A current. What is the voltage at the load (from 208V)? A. 16V B. 192V ✅ C. 208V D. 200V E. 206V Correct Answer: B. 192V Rationale: Total resistance = 0.778 × (500/1000) = 0.389 ohms. Voltage drop = I × R = 42 × 0.389 ≈ 16.34V. Voltage at load = 208 − 16.34 ≈ 192V. 7. Voltage across Lamp 1 in Figure 128.203: A. 120V ✅ B. 0V C. 30V D. 60V E. 240V
Correct Answer: D. 12" Rationale: NEC allows 12" minimum for GFCI-protected circuits in Schedule 40 PVC under residential driveways.
12. What happens if the neutral opens on a multiwire circuit with unequal loads? A. The circuit turns off B. The breaker trips C. Higher resistance load overheats ✅ D. Nothing happens Correct Answer: C. Rationale: An open neutral causes voltage imbalance, and the higher resistance load may overheat due to excess voltage. 13. NEC reference for disconnecting means in multiwire branch circuits (same yoke): A. 240.4(D) B. 210.8(B)(1) C. 240.15(B)(1) ✅ D. 250.52(A) Correct Answer: C. 240.15(B)(1) Rationale: NEC 240.15(B)(1) specifies overcurrent protection for multiwire circuits using shared neutrals and stacked devices. 14. If the neutral is removed from the panel (Figure 128.231), what voltage is applied to the TV? A. 120V B. 0V C. 150V ✅ D. 240V E. 208V Correct Answer: C. 150V Rationale: With the neutral removed in an unbalanced load scenario, voltage can float, often resulting in around 150V on one side, risking damage to sensitive electronics. 15. What happens if the neutral is removed from a split-wired receptacle (12/ cable, 120/240V, 1Φ panel)? A. Breakers trip B. Nothing happens C. Equipment receives lower voltage D. 120V equipment may be destroyed ✅ Correct Answer: D. Rationale: Without a neutral, voltage imbalances result, causing 240V across devices intended for 120V, which can destroy them.
16. Total power drawn by equipment with 4 heating elements at 0.3kW each (connected at T3 & T4): A. 0.3kW B. 0.6kW C. 1.2kW ✅ D. 1.8kW E. 2.4kW Correct Answer: C. 1.2kW Rationale: 0.3 kW × 4 = 1.2 kW total power. 17. Short length of EMT between panels doesn’t require derating if it does not exceed: A. 12 in. B. 36 in. C. 24 in. ✅ D. 18 in. E. 30 in. Correct Answer: C. 24 in. Rationale: NEC allows exemption from ampacity adjustment if the length is ≤24 inches. 18. Extension ladder should extend how far above roofline? A. 1 ft B. 2 ft C. 3 ft ✅ D. Even with roof E. 4 ft Correct Answer: C. 3 ft Rationale: OSHA and ladder safety rules require ladders to extend 3 feet above the landing for safe access. 19. Monthly cost to operate a 250W lamp, 8 hrs/day, 30 days, $0.15/kWh? A. $4. B. $6. C. $9.00 ✅ D. $3. E. $7. Correct Answer: C. $9. Rationale: 250W = 0.25kW × 8 × 30 = 60 kWh × $0.15 = $9.
C. Only with locknut D. No ✅ E. Only in dry locations Correct Answer: D. No Rationale: Self-tapping screws are not a reliable grounding method and are not permitted by the NEC.
25. Minimum conductor size for 100A, 120/240V, 3W service using copper THHN/THWN: A. 6 AWG B. 4 AWG C. 2 AWG D. 3 AWG ✅ E. 1 AWG Correct Answer: D. 3 AWG Rationale: NEC Table 310.16 specifies 3 AWG copper as minimum for 100A service. 26. For noncoincident loads (e.g., AC & heat), what is counted in service calc? A. Both B. 50% of each C. Larger of the two ✅ D. Smaller of the two E. Total wattage Correct Answer: C. Rationale: NEC allows only the larger of two noncoincident loads to be included. 27. A 3/0 conductor is also written as: A. 000 ✅ B. 0/ C. 300 D. 0. E. 30 Correct Answer: A. 000 Rationale: 3/0 AWG = 000 , larger than 2/0 and 1/0. 28. Which NEC table gives demand factors for clothes dryers? A. 220. B. 310.15(B)(16) C. 250. D. 220.54 ✅ E. 240.
Correct Answer: D. 220. Rationale: NEC Table 220.54 is used for calculating clothes dryer loads.
29. Voltage threshold above which NEC requires de-energization and lockout? A. 120V B. 240V C. 50V ✅ D. 30V E. 100V Correct Answer: C. 50V Rationale: NFPA 70E requires lockout/tagout for energized equipment above 50 volts. 30. Are all metal parts of indoor spas required to be bonded? A. Yes ✅ B. No C. Only equipment D. Only structural steel E. Only if GFCI is missing Correct Answer: A. Yes Rationale: NEC mandates bonding of all metal parts to prevent shock hazards. 31. NEC article for swimming pool installations: A. 680 ✅ B. 210 C. 250 D. 430 E. 300 Correct Answer: A. 680 Rationale: Article 680 outlines all pool wiring requirements. 32. Minimum number of convenience receptacles near a permanent pool: A. 0 B. 2 C. 1 ✅ D. 3 E. 4 Correct Answer: C. 1 Rationale: NEC requires at least one 15 - or 20-amp GFCI-protected receptacle within specific distance. 33. Pulling Cat 5 cable too hard can damage: A. Jacket only
C. Secure loosely with other cables D. All of the above ✅ Correct Answer: D. All of the above Rationale: Best practice avoids mechanical stress and maintains signal integrity.
38. RG-6 cable uses which type of connector? A. BNC B. RCA C. RJ D. F connector ✅ E. USB Correct Answer: D. F connector Rationale: F connectors are standard for coaxial RG-6 cable in TV and internet installations. 39. RF-based home automation controllers can: A. Only control lights B. Send signals through walls ✅ C. Only use IR remotes D. Work only on Wi-Fi E. Not operate outside Correct Answer: B. Rationale: RF signals can penetrate walls , enabling control between rooms. 40. Swimming pool pump disconnect must be located: A. In equipment room B. Anywhere on property C. In panel only D. ≥ 5' from inside wall, visible, accessible ✅ E. ≤ 3' from pump Correct Answer: D. Rationale: NEC requires the disconnect to be ≥ 5 feet away , visible, and readily accessible. 41. Receptacles 6'–10' from pool walls for pumps must be: A. Weatherproof only B. Non-grounded C. Grounding type with GFCI ✅ D. 240V E. Hidden Correct Answer: C. Rationale: NEC mandates GFCI and grounding-type for pool area receptacles.
Where contained in a cable , the Code reference that states when a conductor with white insulation may be used as an ungrounded circuit conductor is in Section____. a. 200.6 ( E ) b. 200.7 ( C ) c. 200.9 d.
- ANSWER b. 200.7(C) According to Article 422 , an accessible separable connector or an accessible ____ shall be permitted to serve as the disconnecting means for cord-and-plug - connected appliances a. panel b. device c. method d .plug and receptacle
- ANSWER D Does the NEC permit a 2 - pole circuit breaker to be used as the disconnecting means for a 3.3 KVA , 240 - volt , 10 air compressor? The equipment is installed in the electrical room with and is within sight of the circuit breaker panelboard.
- ANSWER Yes Five 10 AWG THHN / THWN copper current - carrying conductors are installed in a conduit. How much current can each of these carry ( corrected ampacity ) when the conduit is installed in an area where the summertime temperature is 138 ° F? a. 16. b. 28 c. 35 d. 22.
- ANSWER D For Scenario 125.103-240 , amps of current will flow through each heating element. a. 30. b. 120. c. 33. d. 60. e. 66.
- ANSWER D For Scenario 125.103-480 ,____amps of current will flow through each branch circuit conductor. - ANSWER d. 60. Refer to Figure 130.104. In amps , how much current will flow in the circuit conductor , connected to terminal 9 on the 2-pole? a. 20. b. 81. c. 5.
220.52(B) - ANSWER Nameplate or 1500VA is allocated for laundry circuit Overcurrent
- ANSWER Type of circuit condition Ex: overload, short, and ground fault GEC (Grounding electrode conductor)
- ANSWER A conductor used to connect the system grounded conductor or the equipment to a grounding electrode to a point on the grounding electrode system A 100-gallon water heater is to be installed to supply hot water to the restrooms in an office building. Should it be considered a continuous load and be upsized accordingly? - ANSWER Old tank style water heaters 120 gallons or less is considered the continuous duty and requires the conductors to be upsized by 125% 310.12(A) - ANSWER Lists the size of residential service conductors
- 21(B)3 – ANSWER Lists the receptacle sizes per branch circuit sizes. Example you can put a 15a or 20a receptacle on a 20 amp circuit. 210.8 - ANSWER Covers when GFCI protection is required An unfinished basement must have how many outlets that are GFCI protected - ANSWER 1 Service conductors must maintain minimum clearance of___ from doors and windows - ANSWER 3 ' Chapter 9, table 8
- ANSWER Where you can find circular mil area of conductors Dryer load calculation
- ANSWER When performing a load calculation, you must allocate 5KW or the nameplate rating of clothes dryer whichever is higher Dwelling load calc
- ANSWER When performing a load calculation, you must allow 3VA per square foot for dwelling (NEC 220) Electric furnaces are considered continuous duty and required conductors upsized by 125%
- ANSWER
Short circuit
- ANSWER Fault between two or more circuit conductors. Example hot 2 hot hot 2 neutral The greatest number of 120 - volt , 20 - amp circuits you are permitted to install in a house to serve bathrooms is The house has 3 bathrooms and the circuit ( s ) will supply only bathroom receptacles a. 0 b . 1 c. 2 d. 3 e. unlimited
- ANSWER e. Unlimited what is the minimum number of 125-volt, 15- or 20-ampere convenience receptacles that the NEC requires to be installed near a permanently installed pool locates in you neighbors backyard - Ans - one a 20-amp, 120-volt duplex convenience receptacle near a pool shall be located so that it is ___ feet or more from the inside edge of the swimming pool - Ans - 6' Generally, safety switches and wall switches must be located at least ___ from the inside edge of the swimming pool - Ans - 5' When calculating residential service load, ___ is allowed for each branch circuit serving laundry receptacles - Ans - 1,500 volt-amperes the minimum size service disconnect for a single-family dwelling with a computed load of kVA is ___ amperes - Ans - 60 For a 125-amp, 120/240-V, 3W residential service, ____ AWG copper THHN/THWN conductors are the smallest permitted for the underground conductors - Ans - 2 for purposes of calculating a residential service, the general-purpose lighting load is calculated at ___ per sq. ft. of area - Ans - 3 volt-amperes plug fuses can be used on which of the following voltage systems? - Ans - 120/208-volt, 1 - ph, 3-wire 120/208-volt, 3ø, 4-wire (anything under 150- volts)
From NEC table 8 ch. 9 the overall diameter of a 1/0 bare stranded copper is ___ inches - Ans -. what part of the NEC is a reference for calculating conduit fill where all conductors are the same size - Ans - Annex c the number conductor permitted in 80 Pvc is specified in table - Ans - c. 10, Annex C if the leads of the voltmeter are placed at T3 and T4 the meter will indicate - Ans - 120 what is the minimum number of receptacles required in an unfinished basement - Ans - 1 The neutral has been removed from the neutral bar in the circuit shown in the figure. the voltage dropped across lamp 2 is ___ volts - Ans - 80 the load will be energized when the switches are in which condition - Ans - none if the leads of a voltmeter are placed at T1 and T8 the meter will indicate - Ans - 0 how much current is following in the neutral conductor at C inn the figure - Ans - 2 the nuetral conductor carries ___ amps - Ans - 2. circuits 7 and 9 share neutral. this is a multi-wire branch circuit. if ckt 7 is drawing 13 amps and ckt 9 will draw 16 amps, how much current is flowing in the neutral - Ans – 3 The greatest number of 120 - volt , 20 - amp circuits you are permitted to install in a house to serve bathrooms is The house has 3 bathrooms and the circuit ( s ) will supply only bathroom receptacles a. 0 b
. 1 c. 2 d. 3 e. unlimited - ANSWER e. Unlimited The fewest number of 120- volt , 20- amp branch circuits permitted to be installed in a house is_____ when these circuits will supply power to the lighting fixtures ( luminaires ) in bathroom #1 plus the receptacles in all three bathrooms in a house. a. 0 b ......... 11 c .................................................................................................................................... 11 d. 3 - ANSWER c ........................................................... Error! Bookmark not defined. A bathroom vanity lighting fixture will draw_____amps when connected to a 120- volt branch circuit. The fixture has twenty-four lamps installed. Each lamp has a rating of 60 watts at 120 volts. a. (.33) b ........................................... Error! Bookmark not defined.
c. 3 d
. 12 e. (.42) - ANSWER d. 12 A circuit has 4 identical loads connected in parallel. The circuit voltage is 120 volts and the total connected load draws 11.2 amperes of current. The resistance of each of the identical loads is_____ohms a. 6.18 b . 24.73 c . 42. d. 1. e. 45 - ANSWER c. 42. Refer to Figure 115.104. Each of the Type NM cables contains a ground. What is the minimum depth 2 - gang masonry ( brick ) box that could be used here? You will install a second receptacle in this box. The second receptacle is NOT shown. The "pigtails" to both of the receptacles are # 12 wires. As you can see , the cable connectors are external ( outside the box ). a. 1 7/8 b. 2 1/8 c. 2 1/ d. 1 1/ e. 3 1/2 - ANSWER e. 3 1/ See Figure 115.317. The total current drawn by the duct heater when connected to the 208 - volt circuit is_____amps. a. 8.89 b . 15.42 c . 12.31 d . 16. e. 13.52 - ANSWER c. 12. Refer to Figure 110.15 A copper circuit conductor has a resistance of .778 ohm / feet. This circuit feeds a load that is drawing 42 amps. The wire length is 250 feet out to the load plus 250 feet back to the panel. Use Ohm's Law [ E = Ix R ] to find the volts dropped in the circuit conductors and then find how much voltage will be applied to the load. The voltage applied to the load is _____ a. 16 b. 192 c. 208 d. 200 e. 206 - ANSWER b. 192 Refer to Figure 128.203. The voltage across Lamp 1 is______ Volts. a. 120 b. 0 c. 30 d. 60 e. 240 - ANSWER a. 120
b. device c
. method d .plug and receptacle - ANSWER D Does the NEC permit a 2 - pole circuit breaker to be used as the disconnecting means for a 3.3 KVA , 240 - volt , 10 air compressor? The equipment is installed in the electrical room with and is within sight of the circuit breaker panelboard. - ANSWER Yes Five 10 AWG THHN / THWN copper current - carrying conductors are installed in a conduit. How much current can each of these carry ( corrected ampacity ) when the conduit is installed in an area where the summertime temperature is 138 ° F? a. 16. b. 28 c. 35 d. 22.72 - ANSWER D For Scenario 125.103-240 , amps of current will flow through each heating element. a. 30.2 b . 120. c. 33. d. 60. e. 66.2 - ANSWER D For Scenario 125.103-480 ,____amps of current will flow through each branch circuit conductor. - ANSWER d. 60. Refer to Figure 130.104. In amps , how much current will flow in the circuit conductor , connected to terminal 9 on the 2-pole? a. 20. b. 81. c. 5. d. 40. e. 32.7 - ANSWER d. 40. Refer to Figure 130.104. Circuit 14 will draw___amps a. 10.3 b. 78 c. 97.5 d. 84. e. 48.75 - ANSWER c. 97. Refer to Figure 129.105. The voltage applied to element R₂ is____volts. a. 60 b . 120 c . 480 d . 240 e. none of these - ANSWER d. 240
Refer to Figure 119.105. When correctly connected , the dimmer is connected in_____with the two luminaires - ANSWER a. Series Refer connected to Figure 119.105 Schematic Diagram_____( below ) shows the dimmer and the lamps correctly - ANSWER A What is the monthly energy cost to operate a 200 - watt high - pressure sodium lamp? Electricity costs $ 0.11 per kW - hr and the lamp be ON for 12 hours per day. There are 30 days in a billing month. a. $8.8 b. $7.92 c. $6.6 d. $ e. $15.94 - ANSWER b. $7.
- Refer to Figure 128.202. volts are applied across the water heater element. a. 480 b. 0 c. 120 d. 240 - ANSWER d. 240 Refer to Figure 128.202. The neutral conductor carries _____amps. a. 1.07 b . 2.13 c.
d. 4. e. 2.31 - ANSWER b. 2. 220.52(B) - ANSWER Nameplate or 1500VA is allocated for laundry circuit Overcurrent - ANSWER Type of circuit condition Ex: overload, short, and ground fault GEC (Grounding electrode conductor) - ANSWER A conductor used to connect the system grounded conductor or the equipment to a grounding electrode to a point on the grounding electrode system A 100-gallon water heater is to be installed to supply hot water to the restrooms in an office building. Should it be considered a continuous load and be upsized accordingly? - ANSWER Old tank style water heaters 120 gallons or less is considered the continuous duty and requires the conductors to be upsized by 125% 310.12(A) - ANSWER Lists the size of residential service conductors - 21(B)3 - ANSWER Lists the receptacle sizes per branch circuit sizes. Example you can put a 15a or 20a receptacle on a 20 amp circuit. 210.8 - ANSWER Covers when GFCI protection is required
