A current transformer (CT) is rated 600:5 A. If the primary current is 480 A, what is the secondary current?
Measurement Instrumentation
Question · Easy
Which CT accuracy class is typically REQUIRED for protective relaying applications rather than revenue metering?
Question · Medium
Low-resistance resistor placed in parallel with an ammeter to extend the current range it can measure.
Measurement and instrumentation
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Chapter 1: Exam Overview, Strategy & Reference Handbook
1.1 PE Power Exam Format, CBT Navigation & Reference Handbook
Study guide
A megohmmeter reads 250 MΩ on a 480 V motor winding at 40°C. Per IEEE 43, the recommended MINIMUM insulation resistance for this machine (rated voltage + 1 kV at 40°C) is approximately:
Question · Hard
Read the clue and guess the term in 6 tries.
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A polarization index (PI) test on motor insulation gives a 1-minute reading of 200 MΩ and a 10-minute reading of 800 MΩ. The PI is:
Test instrument that combines several electrical measurements in one unit and uses a meter movement.
A potential transformer (PT) is rated 7200:120 V. If the primary voltage is 6900 V, what is the secondary voltage?
A three-phase 4-wire 480Y/277 V system uses three CTs (1200:5) and three PTs (480:120) for revenue metering. The meter multiplier (overall ratio) is approximately:
Intentional or accidental conducting path linking an electrical circuit or equipment to the earth.
General applications
1.2 2026 Reference Standards (NEC 2020, NFPA 70E-2021, NESC) & Scoring Mechanics
A three-point fall-of-potential ground resistance test places the current electrode 100 ft from the grounding electrode under test. The potential probe should be placed at approximately what distance from the grounding electrode for the standard 61.8% rule?
Swap tiles to line up three of the same term.
Term Match
Which instrument is BEST suited to measure true RMS current on a circuit feeding a six-pulse VFD with significant harmonic distortion?
Unit of total luminous flux, realized from the candela.
Two wattmeters connected in the standard two-wattmeter method on a balanced three-phase load read W1 = +6 kW and W2 = +2 kW. The total three-phase power is:
A 20-story office building has a calculated lighting load of 300,000 VA on a 480Y/277 V three-phase service. Per NEC 220.42(A), what demand factor applies to the FIRST 50,000 VA of office lighting?
General Applications
Electric ___ that produces a bright flash of hot gas, with temperatures that can exceed 35,000 °F.
Electrical safety
1.3 CBT Pacing, AIT Question Formats & Formula Sheet Mastery
A lighting designer must achieve 50 footcandles average maintained illuminance over a 40 ft × 30 ft office. Using the lumen method with CU = 0.65 and LLF = 0.75, the required total lamp lumens is approximately:
Flip two cards at a time to find matching terms.
Term Pairs
Per NFPA 780, the rolling-sphere method for lightning protection uses what radius for a Class I structure?
Protective device that compares current going to and returning from equipment and opens the load when the difference reaches about 5 milliamperes.
A surge protective device (SPD) installed at a service entrance must coordinate with downstream branch-panel SPDs. Per UL 1449 4th edition, which SPD type is INSTALLED on the line side of the service disconnect?
A facility's peak demand last month was 2,000 kW with total energy of 720,000 kWh over 30 days. The load factor is approximately:
Hazardous-location area classification whose levels 0, 1, and 2 describe how often ignitable gas or vapor is present.
Chapter 2: Measurement, Metering & Field Testing
2.1 Current Transformers (CTs), Potential Transformers (PTs) & Meter Connections
Per NEC 250.66, a 4/0 AWG copper service-entrance ungrounded conductor requires a grounding electrode conductor of:
Find five hidden terms in a grid of letters.
Term Search
For a building with multiple grounding electrodes (rod, plate, water pipe), NEC 250.50 requires:
___ diagram: drawing of sinusoidal quantities as counterclockwise-rotating vectors, showing, for example, current lagging the applied voltage by 90 degrees in a purely inductive circuit.
Circuit analysis
Lightning protection: in NFPA 780, the side-flash distance from a down-conductor to a metallic body that is NOT bonded to the LPS is governed by:
An energy-management strategy uses a 500 kW peak-shaving battery to reduce a 2,500 kW peak to 2,000 kW. If the demand charge is $20/kW-month, the monthly demand-charge savings is:
Effective value of an alternating current that produces the same heating effect as an equal direct current.
2.2 Instrument Transformer Burdens, Saturation Curves & Ratio Correction Factors
A surface installation is required for an LED parking-lot luminaire on a steel pole. To resist lightning surges, the down-conductor on the pole should be sized at no less than which copper cross-section per NFPA 780 for a Class I (ordinary) structure?
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Per NEC 2020 Table 220.12, an office building requires what unit lighting load (VA per ft²) for branch-circuit and feeder calculations?
Most commonly used ASD: an electronic motor-speed controller that changes how often the supply to an AC motor alternates, also known as a VSD.
Power electronics
A 100 kW continuous resistive load on a 480/277 V three-phase 4-wire system. What MINIMUM line current must the OCPD be sized for, considering NEC 215.3 / 210.20 continuous-load rules?
Electrical Safety
Per NEC 2020 Table 310.16 (75°C column), three current-carrying 4/0 AWG THWN copper conductors in raceway have an ampacity of:
Sampling technique that produces a constant-amplitude rectangular wave whose on-time varies.
2.3 Insulation Resistance Testing (Megger, Polarization Index, Dielectric Absorption)
Eight current-carrying 12 AWG THHN copper conductors share a single conduit at 30°C ambient. Per NEC 2020 Table 310.15(C)(1), the ampacity adjustment factor is:
A Class I, Division 1, Group D location includes which of the following hazardous atmospheres per NEC 500?
Fraction by which an induction motor's shaft speed falls short of the rotating field's speed.
Rotating machines
Per NFPA 70E-2021, the arc-flash boundary is defined as the distance at which incident energy equals:
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