Mixed Deck — All EETC Topics Flashcards

What is the maximum trade size for electrical nonmetallic tubing (ENT) permitted by the NEC?

Answer: 3 inches

NEC 362.20 limits ENT to a maximum trade size of 2 inches; larger sizes are not listed or manufactured for ENT.

A 'saddle bend' (four-bend saddle) in conduit is used to:

Answer: Pass the conduit over a pipe or obstruction while returning to the original plane

A four-bend saddle uses two pairs of equal opposing bends to rise over an obstacle and return to the original pathway height, allowing the conduit to bridge obstructions like pipes or beams.

Which ISA instrument tag designation indicates a flow indicating controller?

Answer: FIC

Per ISA-5.1, F=Flow, I=Indicating, C=Controller, so FIC is a flow instrument that both displays the measured value and provides control output.

A 20A, 120V circuit feeds a continuous load. Per NEC 210.20, the circuit's overcurrent device must be rated at least:

Answer: 25A

NEC 210.20(A) requires the overcurrent device to be rated at 125% of the continuous load current (20A × 1.25 = 25A).

Which document defines the national minimum safety standard for electrical installations in the United States?

Answer: NFPA 70 (National Electrical Code)

NFPA 70, the National Electrical Code (NEC), is the nationally recognized minimum safety standard for electrical installations in the US.

Apparent power (S) in an AC circuit is the vector sum of real power (P) and reactive power (Q). The correct relationship is:

Answer: S = √(P² + Q²)

Apparent power S = √(P² + Q²), forming the hypotenuse of the power triangle with real and reactive power as legs.

Which approach best demonstrates mastery of power distribution in EETC practice?

Answer: Applying principles to novel situations with sound judgment

True mastery involves understanding underlying principles well enough to apply them to new and unfamiliar situations with professional judgment.

Cable tray systems installed in industrial facilities may contain:

Answer: Power and communication cables provided they are separated in accordance with NEC Article 392

NEC Article 392 permits cable tray to contain power, control, signal, and communication cables, but requires separation between power and communication cables to prevent interference and meet safety requirements.

Which enclosure type is rated for outdoor use and protection against rain, sleet, and snow according to NEMA standards?

Answer: NEMA 4

NEMA 4 enclosures are weatherproof and protect against rain, sleet, snow, windblown dust, and hose-directed water.

What is the function of a soft starter compared to an across-the-line starter?

Answer: A soft starter gradually ramps up voltage to reduce mechanical shock and inrush current during starting

A soft starter uses SCRs to gradually increase voltage from zero to full value, reducing mechanical shock, inrush current, and torque pulsations.

What is the function of a system bonding jumper in a separately derived system?

Answer: It bonds the grounded conductor to the supply-side equipment grounding conductor or enclosure at the source

The system bonding jumper, required by NEC 250.30(A)(1), connects the grounded conductor of a separately derived system to the supply-side EGC or enclosure at the system source.

In the Superposition Theorem, when analyzing the effect of one source, all other independent voltage sources are:

Answer: Replaced with short circuits

When applying the Superposition Theorem, independent voltage sources not being analyzed are replaced with short circuits (zero voltage).

When running Type NM cable through a 2x4 wood stud, what is the minimum distance the cable must be from the edge of the stud before a nail plate is required?

Answer: 1¼ inches

NEC 300.4(A)(1) requires a steel nail plate or the cable must be at least 1¼ inches from the nearest edge of a stud to protect against fastener penetration.

In PLC-based motor control, what is a 'rung' in ladder logic?

Answer: A horizontal line in a ladder diagram representing one control logic statement

A rung is one horizontal row in a PLC ladder diagram, containing input conditions (contacts) and one or more output coils or instructions.

What happens to the magnetizing current in a transformer when the core becomes saturated?

Answer: It increases sharply and becomes non-sinusoidal

Core saturation causes a sharp, non-linear rise in magnetizing current and introduces harmonic distortion.

A 20-amp, 120-volt bathroom receptacle circuit must be:

Answer: GFCI protected only

NEC 210.8 requires all bathroom receptacles to have GFCI protection due to proximity to water sources.

In a forward/reverse motor control circuit, what prevents both forward and reverse contactors from energizing simultaneously?

Answer: Electrical and mechanical interlocks

Electrical interlocks (NC auxiliary contacts) and mechanical interlocks prevent both contactors from closing simultaneously, avoiding a phase-to-phase short circuit.

What is the primary cause of 'ferroresonance' in distribution systems?

Answer: Interaction between transformer magnetizing inductance and system capacitance under light or no-load conditions

Ferroresonance occurs when the nonlinear magnetizing inductance of an unloaded or lightly loaded transformer resonates with cable or capacitor charging capacitance, producing overvoltages.

What is the effect of placing two coils with the same address (bit) in different rungs of a ladder logic program?

Answer: The last coil scanned determines the final state of the bit

Duplicate output coils are a programming error; during each scan, the final coil instruction for a given address overwrites earlier ones, causing unpredictable behavior.

What is the first step in troubleshooting a circuit?

Answer: Ensure the circuit is de-energized

Before beginning any troubleshooting or repair work on an electrical circuit, the absolute first step is to ensure that the circuit is completely de-energized. This critical safety measure prevents accidental electrical shock or electrocution. After turning off the power at the breaker or switch, it is essential to verify the absence of voltage using a reliable testing device.