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Quizzes > Electronics & Gadgets

Chicago supervising electrician practice test: exam-style questions

Quick, free quiz with Chicago electrical exam practice test questions. Instant results.

Editorial: Review CompletedCreated By: Jesmin SultanaUpdated Aug 28, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration showing exam sheet checklist pencil light bulb and plug icons on coral background

This quiz helps you prepare for the Chicago Supervising Electrician exam with realistic NEC code, wiring, and load calculation questions. Review conduit fill, fault current, and job-site scenarios, then see what to study next. For extra practice, try our industrial electrician practice test or build fundamentals with an electrician quiz.

Which conductor color indicates an equipment grounding conductor in most electrical installations?
Black
White
Red
Green
Per NEC 250.119, equipment grounding conductors are identified by continuous green insulation or green with a yellow stripe. This differentiates them from neutral (white) and phase conductors (black, red). Proper color coding ensures a clear grounding path and enhances safety.
What is the standard voltage for a single-phase branch circuit outlet in residential buildings?
120 V
240 V
277 V
480 V
Most U.S. homes use 120 V branch circuits for general-purpose outlets, as specified in NEC Article 210.11. This voltage accommodates lighting and small-appliance loads. Higher voltages such as 240 V are reserved for heavy appliances.
What is the minimum number of 20 A small-appliance branch circuits required in a residential kitchen?
Two
Three
One
Four
NEC 210.52(B) mandates at least two 20 A small?appliance branch circuits for kitchen countertop and dining areas. This ensures sufficient capacity for modern appliances. Circuits must serve no other loads.
#14 AWG copper THHN wire has an ampacity rating of ____ under normal conditions?
30 A
20 A
25 A
15 A
According to NEC Table 310.15(B)(16), #14 AWG copper THHN is rated for 15 A at 60 °C. This limits its use on circuits requiring overcurrent protection not to exceed 15 A. Using larger conductors is required for higher ampacities.
What does NEC stand for?
National Electrical Code
National Energy Code
National Engineering Code
National Electronic Code
The acronym NEC stands for National Electrical Code, which is the U.S. standard for safe electrical design, installation, and inspection. It is published by NFPA and adopted in nearly all jurisdictions. The NEC is updated every three years.
How many separate conductors are in a typical single-phase 120/240 V residential service drop?
Two
Five
Three
Four
A single?phase 120/240 V service drop contains two ungrounded (hot) conductors and one grounded (neutral) conductor. These three conductors deliver both 120 V (to neutral) and 240 V (between hots). Equipment grounding is local and not part of the overhead drop.
Which color designates a grounded (neutral) conductor?
Green
Blue
Red
White
Per NEC 200.6, grounded (neutral) conductors shall be white or natural gray. This is to distinguish them from ungrounded (hot) conductors which are colored. Consistent use prevents improper connections.
Conduit fill calculations are based on which conductor characteristic?
Conductor length
Insulation thickness
Weight per foot
Cross-sectional area
NEC Chapter 9, Table 1 requires conduit fill to be calculated using the conductor's cross-sectional area. This ensures the conduit has enough space for heat dissipation and future pulling. Overfilling can lead to overheating and damage.
What device protects against overloads by interrupting current flow when it exceeds a set value?
Ground rod
Circuit breaker
Contactor
Transformer
Circuit breakers are overcurrent protective devices that trip automatically when current exceeds their rating. They protect conductors and equipment from thermal and magnetic overload damage. They can be reset after tripping, unlike fuses.
In dwelling units, receptacle outlets along walls must be installed at intervals not exceeding ____.
4 feet
8 feet
6 feet
12 feet
NEC 210.52(A)(1) specifies receptacle spacing so that no point along the floor line is more than 6 ft from an outlet, requiring spacing at intervals of 12 ft maximum. This accommodates typical appliance cord lengths. It ensures convenience and safety.
Which of the following is required for bathroom receptacle outlets?
GFCI protection
Surge protection
AFCI protection
Time?delay switch
NEC 210.8(A)(1) mandates GFCI protection for receptacles in bathrooms to prevent shock hazards. Ground-fault protection quickly interrupts current when an imbalance is detected. This reduces the risk of electric shock near water.
Where must the service disconnecting means be located relative to the meter in most residential installations?
Within 20 feet
Within 3 feet
Within 6 feet
Within 10 feet
NEC 230.70(A)(1) requires the service disconnect to be at a readily accessible location at or near the point of entrance. Typically this is within 6 ft of the meter. This provides quick shutoff in emergencies.
Which type of conduit is most commonly used for underground installations?
PVC schedule 40
Rigid metal conduit (RMC)
EMT
FMC
PVC schedule 40 conduit is widely used underground due to corrosion resistance, low cost, and ease of installation. It meets NEC Article 352 requirements for underground installations. Metal conduits are heavier and require corrosion protection.
What is the maximum VA load allowed on a single small?appliance branch circuit per NEC?
2500 VA
2000 VA
1000 VA
1500 VA
NEC 220.52(B) requires each small-appliance branch circuit to be calculated at 1500 VA. This ensures adequate capacity for countertop appliances. Circuits cannot serve lighting or other loads.
Which device interrupts current when a ground fault exceeds a predetermined threshold?
MCB
RCD
AFCI
GFCI
Ground-Fault Circuit Interrupters (GFCIs) detect imbalances between hot and neutral conductors. When current leakage exceeds about 5 mA, they trip almost instantly. This protects against electrocution.
What is the maximum recommended voltage drop for branch circuits to maintain efficiency and proper operation?
1%
10%
5%
3%
Industry best practice recommends a maximum of 3% voltage drop on branch circuits (plus 3% on feeders) for efficient operation. While not strictly enforced by NEC, it helps maintain motor performance and equipment lifespan. Proper conductor sizing reduces losses.
When more than three current-carrying conductors are installed in a single raceway, what ampacity adjustment factor must be applied to each conductor?
80%
70%
100%
60%
NEC 310.15(B)(3)(a) requires applying an 80% ampacity factor when 4 - 6 current-carrying conductors share a raceway. This derating prevents overheating due to mutual heating effects. Proper adjustments ensure conductor insulation integrity.
A run of #3 AWG copper conductor is 100 ft long and carries 120 A. Using 3% maximum drop at 240 V feeder, what minimum size conductor would you choose?
3 AWG aluminum
4 AWG copper
2 AWG copper
1 AWG copper
A voltage drop calculation shows #3 copper at that length and load exceeds 3% drop. Upsizing to 2 AWG copper reduces resistance and keeps drop under 3%. NEC recommends maintaining voltage drop under 5% combined feeder and branch.
What is the maximum fill percentage for conductors in a circular conduit with more than two conductors, according to NEC Chapter 9?
75%
53%
40%
31%
Per NEC Chapter 9, Note 9, conduit fill for three or more conductors must not exceed 40% of the internal cross-sectional area. This limit ensures adequate space for conductor movement and heat dissipation. Overfilling risks damage during installation and operation.
How is the demand load for household electric dryers calculated under NEC Article 220?
7 kW
3 kW
5 kW
2 kW
NEC 220.54 specifies a 5 kW demand load for each household electric dryer. This standardized value simplifies feeder and service calculations. It ensures capacity for typical dryer usage without oversizing circuits.
Which article of the NEC covers conductor temperature correction factors?
310.15(B)(1)
250.122
110.14(C)
210.19(A)
NEC 310.15(B)(1) provides temperature correction factors for conductors based on ambient temperature and insulation rating. Adjustments ensure conductors operate within safe thermal limits. Following these factors prevents insulation degradation.
In a multiwire branch circuit, what must be provided to simultaneously disconnect all ungrounded conductors?
Common disconnect
Individual fuses
Lockout tag
Separate breakers
NEC 210.4(B) requires a means to simultaneously disconnect all ungrounded conductors of a multiwire branch circuit. This prevents feedback and potential shock during maintenance. Common-trip breakers or handle ties satisfy the requirement.
What type of overcurrent protection device is required for a motor branch circuit to guard against single-phasing?
Overload relay
Time?delay switch
GFCI breaker
Fuse
Per NEC 430.32, motor branch circuits must include overload protection, such as a thermal or magnetic overload relay, to guard against overcurrent and single-phasing. This device senses current imbalance and protects winding insulation. Fuses alone don't guard against single-phasing.
Which NEC table is used for selecting neutral and grounding conductor sizes?
Table 408.4
Table 250.122
Table 310.15(B)(16)
Table 240.4
NEC Table 250.122 specifies minimum sizes for equipment grounding conductors based on overcurrent device ratings. It ensures adequate fault-clearing paths. Other tables cover different conductor ampacities.
Which conductor insulation type has the highest temperature rating among common building wires?
THHN
UF
SE
NM?B
THHN (Thermoplastic High Heat?resistant Nylon) is rated at 90 °C in dry locations, higher than NM-B (60 °C) or UF (60 °C). This allows higher ampacity under certain conditions. THHN's nylon jacket also resists abrasion.
What is the minimum distance a transformer secondary terminal must be from the floor to qualify as readily accessible?
18 inches
No minimum; must be accessible
6 inches
12 inches
NEC Article 450 doesn't impose a floor?height clearance for accessible transformer terminals; it only requires them to be readily accessible. 'Readily accessible' means without requiring tools or climbing. This ensures quick service and emergency access.
A feeder supplies a continuous load of 90 A at 75 °C ambient. What size copper conductor at 75 °C rating is required per NEC 215.2?
1 AWG
4 AWG
3 AWG
2 AWG
NEC 215.2(A)(1) requires sizing feeders at 125% for continuous loads. 90 A × 1.25 = 112.5 A. Per Table 310.15(B)(16), 3 AWG copper THHN (rated 115 A at 75 °C) is the minimum. This ensures safe continuous operation.
Which NEC section covers ground-fault protection of equipment for solidly grounded wye systems?
250.4
240.13
230.95
210.8
NEC 240.13 requires ground-fault protection of equipment (GFPE) for solidly grounded wye systems at alternators and transformers above 150 V to ground. This protects equipment from damage due to ground faults. It's separate from personnel protection devices.
What is the maximum number of conductors permitted in an outlet box before box fill calculations are required?
Five
Four
Two
Three
NEC 314.16(B) notes box fill calculations apply once more than two conductors are present. Each conductor requires a defined cubic-inch volume in the box to prevent overcrowding. Box fill ensures safe wire bending and heat dissipation.
Which of the following requires GFCI protection per NEC 210.8(A)?
Outdoor receptacles
Bedroom receptacles
Hallway receptacles
Living room receptacles
NEC 210.8(A)(3) requires GFCI protection for outdoor receptacles to protect against ground faults in wet conditions. Indoor living areas do not generally require GFCI unless near water. Outdoor protection is vital for safety.
What is the minimum size copper equipment grounding conductor for a circuit protected at 100 A?
8 AWG
10 AWG
4 AWG
6 AWG
NEC Table 250.122 specifies an 8 AWG copper equipment grounding conductor for a 100 A overcurrent device. This ensures a low-impedance path for fault currents. Undersizing can delay trip times.
A 480 V Y-connected transformer has a 120 V secondary. What is its turns ratio (primary to secondary)?
4:1
3:1
1:3
1:4
The turns ratio equals primary voltage divided by secondary voltage: 480 V/120 V = 4:1. This means four primary turns per secondary turn. Correct ratio is critical for proper voltage transformation.
How do you calculate the symmetrical fault current at the secondary of a 500 kVA, 480/120 V transformer with %+ impedance of 5%?
50,000 A
10,417 A
20,833 A
5,000 A
Fault current = (Transformer kVA × 1000) / (?3 × V_sec × %Z). For single-phase secondary: (500 kVA×1000)/(120 V×0.05)=20,833 A. High fault currents require proper OCPD selection.
Which NEC article covers calculation methods for emergency and standby power systems load?
690
700 and 701
620
702
NEC Articles 700 and 701 cover emergency and legally required standby systems, including load calculations and transfer equipment. They specify required minimum loads and transfer timings. These ensure essential loads remain powered.
A single-phase motor nameplate shows 460 V, 30 A full-load current. What size fuse does NEC 430.52 recommend as maximum rating?
30 A
36 A
45 A
50 A
NEC 430.52 allows fuses up to 175% of motor full-load current for single-phase motors. 30 A × 1.75 = 52.5 A, so the next standard size 45 A is acceptable, but 36 A is below rating. Maximum recommended is 45 A.
What is the maximum allowable overcurrent protection for a transformer secondary conductor sized per 75% of OCPD rating under NEC?
150%
100%
80%
125%
NEC 450.3(B) permits transformer secondary conductors to be sized at 125% of the overcurrent device rating when the device is located on the primary side. This safeguards the primary winding. Ensures secondary conductors handle transformer inrush.
Which of the following is the correct method to ground a separately derived system?
Use the equipment grounding conductor without electrode
Ground only one phase conductor
Connect a grounding electrode conductor to the neutral at the transformer
Bond each phase to earth independently
NEC 250.30 requires separately derived systems (like transformers) to have the derived neutral grounded to the grounding electrode system at the transformer location. This provides a reference plane for system voltages and a path for fault currents. Proper bonding prevents floating neutrals.
A feeder supplies a building with a calculated load of 350 A. According to Chicago code amendments, what minimum rating switch must be used for the service disconnect?
400 A
350 A
600 A
250 A
Chicago Municipal Electrical Code requires the service disconnect to be rated not less than the calculated load. A 350 A load calls for the next standard higher rating of 400 A. This ensures safe overcurrent protection.
Calculate the voltage drop for a 200 ft round-trip copper feeder carrying 150 A in #2 AWG conductors (resistance 0.156 ?/1000 ft).
15.6 V (?2.6%)
3.12 V (?0.52%)
4.68 V (?0.78%)
7.80 V (?1.3%)
Voltage drop = I × R_total. R_total = 0.156 ?/1000 ft × 200 ft = 0.0312 ?. Drop = 150 A × 0.0312 ? = 4.68 V, which is 4.68/120 ?3.9% if on a 120 V circuit, or 0.78% on 480 V. Proper sizing keeps drop low.
Which NEC section governs arcs flashing hazard analysis and PPE requirements?
240.87
300.5
250.102
110.16
NEC 110.16 requires arc?flash hazard warning labels and PPE. It defines the hazard boundaries and specifies labeling requirements for equipment likely to require examination while energized. Compliance reduces risk of injury.
A 200 A service uses a 3-wire 120/240 V single-phase meter socket. Under Chicago rules, what additional conductor is required in the service cable?
Additional neutral
Separate equipment grounding conductor
No additional conductor
Fourth hot conductor
Chicago further requires a separate equipment grounding conductor in the service entrance cable to ensure grounding continuity. The neutral in the meter loop cannot serve as equipment ground under some local amendments. This enhances fault clearing.
Which calculation method is acceptable for sizing service load based on apartment house without individual dwelling unit meter?
NEC 220.84 demand factors
NEC 220.65 continuous load
NEC 220.42 general lighting
NEC 220.82 resident packing
NEC 220.84 provides demand factors for apartment houses without individual unit metering, allowing less than sum of loads. This produces realistic service sizing. Other methods do not address multi-unit scenarios.
For a new service, what is the minimum conductor size for ungrounded conductors serving a 200 A residential panelboard?
2 AWG copper
3 AWG copper
1 AWG aluminum
4 AWG copper
NEC 310.15(B)(7) permits #2 AWG copper conductors for a 200 A panel using 75 °C column ratings, delivering 205 A. #3 AWG is limited to 175 A. Compliance ensures proper ampacity.
What is the required maximum impedance of a grounded service conductor to limit voltage rise under fault conditions?
3 ?
15 ?
25 ?
10 ?
NEC Annex D suggests that grounding electrode system impedance should not exceed 25 ? ideally, but some authorities require 5 ? or 3 ? to ensure quick clearing. Chicago often follows 3 ? for service grounding. Low impedance ensures effective fault clearing.
Under Chicago amendments, what additional requirement applies to grounding electrode systems for buildings over three stories tall?
Use 2-inch diameter rod only
Install additional ground rods every 100 ft perimeter
Bond only natural gas piping
No additional requirement
Chicago Municipal Code requires buildings over three stories to have supplementary ground rods every 100 ft of perimeter to improve fault dissipation. This exceeds NEC's 25 ? recommendation. It addresses local soil conditions and public safety.
Which NEC rule allows attachment plug caps and connectors to be installed on flexible cords for lighting fixtures?
411.4(D)
210.8
240.21
400.7
NEC 411.4(D) permits specific fittings on flexible cords for luminaries and lighting fixtures, with plug caps or connectors listed for such use. This exception allows fixture removal without hard wiring. Other articles have broader restrictions.
A transformer secondary is tapped at 80% of its capacity per NEC. Under what conditions is this allowed?
Under 3-phase dry-type transformer taps per 450.3(B)
Never allowed
Only for grounding conductor taps
Only on single-phase liquid-filled
NEC 450.3(B) allows transformer taps up to 125% on primary but secondary taps under limited conditions on 3-phase dry-type are permitted within the temperature rating and listed tap range. This provides voltage adjustment. Liquid-filled transformers have different rules.
For a service equipment switchboard located outdoors, which additional clearance is required by Chicago code over NEC?
3 feet rear clearance
No top clearance
1 foot front clearance
2 feet on the sides for maintenance access
Chicago amendments add 2 ft of side clearance for outdoor switchboards to allow maintenance and meet local fire department access requirements. NEC requires 36 in front and 30 in rear but no side. This improves safety in urban installations.
What is the maximum rating of a service disconnect tap conductor allowed under NEC 240.21(B)(2) without an overcurrent device at the tap?
Tap conductors up to 25 ft long sized 135% of OCPD
Only 4 ft long at 100%
Tap conductors up to 10 ft at 150%
Unlimited length at 100%
NEC 240.21(B)(2) permits service tap conductors up to 25 ft protected at 135% of ampacity without an intermediate overcurrent device if run to service disconnects. This eases equipment placement. Exceeding these limits requires full OCPD protection.
Under NEC 215.10, when are grounded conductors prohibited from being used for backfeeding busways?
When the busway is not listed for backfeeding
Only for transformers
Always allowed
Never allowed
NEC 215.10(B) prohibits using grounded conductors for backfeeding busways unless the busway is explicitly listed for that purpose. This prevents overloading neutrals or grounds. Listed equipment ensures safe backfeed connections.
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Study Outcomes

  1. Apply National Electrical Code Requirements -

    Use our free electrical exam practice test with realistic electrician test sample questions to apply key NEC regulations for the Chicago Supervising Electrician license.

  2. Analyze Test Questions to Identify Knowledge Gaps -

    Review your responses to pinpoint specific code areas where you need additional study or clarification.

  3. Interpret Complex Wiring Scenarios -

    Tackle scenario-based questions modeled after national electrical code practice tests to build real-world troubleshooting skills.

  4. Evaluate Exam Readiness -

    Track your progress across multiple practice attempts to assess when you're fully prepared to sit for the Chicago electrical license exam.

  5. Strengthen Problem-Solving Strategies -

    Hone your approach to electrical exam test questions with tips on time management and logical reasoning.

Cheat Sheet

  1. NEC Conductor Ampacity -

    Review NEC Article 310 tables to determine conductor ampacity under various temperature and bundling conditions, a common electrician test sample topic. Understand derating factors for multiple conductors in a raceway and temperature corrections to avoid overloading. Mnemonic: "Triple Bundles? Triple Derate!" helps recall when three or more conductors share a conduit (NFPA 70).

  2. Load Calculation Methods -

    Master NEC Article 220 demand factors for lighting, appliances, and motor loads - key for your electrical exam practice test. Practice a sample calculation: for a 200 A service, apply 3 kVA for the first three family units and 2 kVA for each additional unit. Remember "First Three, Big Fee" to lock in that initial 3 kVA per family unit (IEEE guidelines).

  3. Ohm's Law & Power Formulas -

    Solidify V=IR, I=P/V and P=I²R relationships, as many national electrical code practice test questions hinge on these basics. Use the Ohm's Law triangle or the "VIP" mnemonic (Voltage top, I and R at corners) for quick recall. Practice solving variations under timed conditions to simulate real exam pressure (IEEE Education Society).

  4. Grounding vs. Bonding Essentials -

    Distinguish grounding (electrodes to earth) from bonding (metal parts connected) per NEC Article 250, a frequent point on the Chicago electrical license exam. Know sizing for equipment grounding conductors and see sample charts in official NFPA handbooks. Mnemonic: "Bond to Guard, Ground to Earth" cements their different safety roles.

  5. Conduit Fill & Tray Calculations -

    Learn NEC Chapter 9 fill percentages - 53% for one cable, 31% for two, and 40% for more - critical for conduit sizing questions on your electrical exam test questions. Practice with sample tables to calculate max cable diameters in EMT or PVC conduit. Tip: "One-Five-Three, One Cable's Free" for easy recall.

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