Free NATE Core Practice Test

Answer: D. Section 8

OSHA's standard SDS format puts exposure controls and personal protection in Section 8. Section 1 identifies the product and supplier, Section 4 covers first aid, and Section 9 lists physical and chemical properties.

Source: OSHA 29 CFR 1910.1200 Appendix D, Table D.1.

Answer: A. Schematic (ladder) diagram

A ladder diagram shows how the circuit works electrically: what's in series with what, and the conditions that energize a load. A wiring diagram shows physical layout and where each wire lands, not the operating logic. A nameplate lists ratings, and a floor plan shows the building.

Source: Basic Motor Control (BCcampus): Schematic vs. Wiring Diagrams.

Answer: D. It is cut in half

Ohm's law: I = V / R. Hold V steady and double R, and I drops to half. Current doubling would need the resistance cut in half. "Stays the same" ignores R, and a fourfold increase contradicts the inverse relationship. The resistive DC condition matters: coils and motors on AC also have reactance, so V/I on them isn't simple resistance.

Source: OpenStax College Physics 2e, 20.2 Ohm's Law.

Answer: C. Below 60%, ideally 30 to 50%

EPA says to keep indoor humidity below 60 percent, ideally between 30 and 50 percent. The 60 to 70% and above-70% choices exceed that recommendation; 60% is not a universal threshold below which mold cannot grow. Very dry air under 20% isn't the target either.

Source: EPA: A Brief Guide to Mold, Moisture and Your Home.

Answer: A. Latent heat

For a pure substance changing phase at constant pressure, energy can go in without changing temperature. That's latent heat. Sensible heat shows up as a temperature change on a thermometer, which isn't happening here. Specific heat is a property of a material (heat per pound per degree), not the heat being added. Radiation is just one way heat can travel. The same idea explains why an evaporator absorbs so much heat while refrigerant boils inside it.

Source: OpenStax College Physics 2e, 14.3 Phase Change and Latent Heat.

Answer: A. To remove the inside burr that can cause turbulence and erosion-corrosion

A wheel cutter rolls a burr into the tube. If it's left in, it causes local turbulence and higher flow velocity, which can lead to erosion-corrosion. Reaming doesn't thin the wall or anneal (soften) the copper, and it works on the inside edge, not the outside diameter.

Source: Copper Development Association, Copper Tube Handbook: Reaming.

Answer: C. Wiring (connection) diagram

Wiring diagrams show how equipment is laid out and the physical connections between devices. A ladder diagram's layout has nothing to do with where parts sit in the cabinet. A psychrometric chart is for air properties, and a sequence of operation describes what happens, not where wires go.

Source: Basic Motor Control (BCcampus): Schematic vs. Wiring Diagrams.

Answer: D. You, the authorized employee doing the servicing, with your own lock

OSHA says lockout or tagout is performed only by the authorized employees who are doing the servicing. Your lock keeps control of the energy source in the hands of the person exposed to it. An untrained helper's lock is not a substitute for your personal protection under this procedure, a homeowner cannot take your place, and a label on a breaker isn't a lockout device at all. Group lockout has separate requirements.

Source: OSHA 29 CFR 1910.147.

Answer: A. The R-19 wall resists conductive heat flow more

R-value is thermal resistance. The rate of conductive heat transfer is inversely proportional to R, so the larger the R, the better the insulation. Higher R means slower heat flow, not faster, and the two walls won't match. Insulation doesn't produce heat.

Source: OpenStax College Physics 2e, 14.5 Conduction.

Answer: D. The contact opens, the coil drops out, and the motor stops

Overload relays use normally closed contacts in series with the contactor coil. Excess current heats the sensing element, the contact opens, the coil de-energizes, and the contactor drops out. The motor stops rather than slowing, reversing, or running on. The thermal overload has to cool before it can be reset.

Source: Basic Motor Control (BCcampus): Overload Relays.

Answer: D. Don't stand on the top step; use a taller ladder or other suitable access

OSHA's construction ladder rule says the top or top step of a stepladder shall not be used as a step. No exception exists for a helper, a short job, or staying under the duty rating. The fix is the right height of ladder or a different way to reach the work.

Source: OSHA 29 CFR 1926.1053.

Answer: C. 21,600 Btu/h

Btu/h = 1.08 × CFM × ΔT = 1.08 × 1,000 × 20 = 21,600. The 1,080 answer leaves out the temperature rise, 18,519 divides by 1.08 instead of multiplying, and 43,200 doubles the right answer. Here 1.08 = 60 minutes/hour × 0.075 lb/ft³ × 0.24 Btu/(lb·°F). It depends on the stated air properties and Fahrenheit temperature difference; it is not a universal constant for all conditions.

Source: OpenStax College Physics 2e, 14.2 Temperature Change and Heat Capacity.

Answer: C. 110 psia

At fixed volume, absolute pressure rises in proportion to absolute temperature: P2 = 100 × 330 / 300 = 110 psia. 90.9 flips the ratio. 100 ignores the temperature change. 211 comes from wrongly using rounded Celsius temperatures (27°C to 57°C). Gas-law math needs kelvin (or Rankine) and absolute pressure, never gauge readings or °C/°F.

Source: OpenStax College Physics 2e, 13.3 The Ideal Gas Law.

Answer: A. The unit is oversized and short-cycling, so it removes less moisture

An oversized single-stage unit can satisfy the thermostat in short runs without removing enough moisture, leaving the house cold but damp. An undersized unit would tend to run longer, not produce the confirmed capacity mismatch. A high setpoint does not explain this case, and the stated normal airflow rules out a filter restriction as the explanation. Short cycling has other possible causes when those checks have not been made.

Source: ENERGY STAR: Right-Sized Air Conditioners (fact sheet).

Answer: A. The coil's magnetic field pulls in the armature, closing the main contacts to power the compressor and fan

Current through the coil creates a magnetic field that pulls the armature in, closing the contacts and powering the load. That's how a small control current switches a large load. The coil closes normally open main contacts, it doesn't open them. The transformer supplies the 24 V, it doesn't step up, and the overload only needs resetting after it has tripped.

Source: Basic Motor Control (BCcampus): Magnetic-Motor Starters.

Answer: C. Nonconductive side rails

OSHA requires nonconductive side rails when the worker or the ladder could contact exposed energized equipment. Aluminum conducts. A duty rating is about load, not electrical protection, and rubber feet don't protect you from contact at the rails. This rule doesn't make working near exposed live parts acceptable by itself; the other electrical safety rules still apply.

Source: OSHA 29 CFR 1926.1053.

Answer: A. Get the nut on first: slide it on from the other end (threads toward the flare) if that end is free, otherwise cut off the flare and re-flare

The flare is wider than the nut's bore, so the nut has to go on before you flare, threads toward the end being flared. Forcing or heating will damage the flare or the nut. A larger nut is not a substitute for the matching nut and fitting.

Source: Copper Development Association, Copper Tube Handbook, 2010 text copy, pp. 52–53: Flared Joints.

Answer: B. 3 tons

One ton of cooling is 12,000 Btu/h, so 36,000 ÷ 12,000 = 3 tons. 1.5 uses 24,000 per ton, 3.6 uses 10,000, and 36 uses 1,000.

Source: NIST Guide to SI, Appendix B.8: ton of refrigeration (= 12,000 Btu IT/h).

Answer: B. In the circuit during both starting and running

"Permanent" means the capacitor stays in the circuit during both starting and running. It is in series with the auxiliary winding, not the main winding. A capacitor-start design switches its starting capacitor out; a PSC capacitor is not used only for reversal. The PSC trade-off is lower starting torque than a capacitor-start design.

Source: All About Circuits: Single-phase Induction Motors.

Answer: C. 20 feet

OSHA sets 20 feet, or the 5-foot barrier with at least a half-hour fire-resistance rating, for oxygen cylinders in storage. The 5-foot figure is the barrier height, not the separation distance, and neither 10 nor 50 feet is the rule.

Source: OSHA 29 CFR 1910.253.

Answer: D. Faster recirculation moves more indoor air but doesn't mechanically bring in outdoor air

EPA notes that most home heating and cooling systems, including forced-air systems, don't mechanically bring fresh air into the house. Outdoor air gets in by infiltration or by ventilation that's actually designed in. Speeding up a recirculating blower doesn't create a controlled outdoor-air supply. Returning more indoor air to the blower is not the same as bringing outdoor air into the house.

Source: EPA: Improving Indoor Air Quality.

Answer: D. 90 lb/ft³

Density is mass per unit volume: 45 ÷ 0.5 = 90 lb/ft³. 22.5 multiplies instead of dividing, 0.011 ft³/lb is the inverse (volume per pound), and 45.5 just adds the numbers.

Source: OpenStax College Physics 2e, 11.2 Density.

Answer: B. Capacitor-start

A capacitor-start motor uses a larger capacitor during starting and switches it out at speed, which gives more starting torque. Shaded-pole motors have minimal starting torque, PSC motors have lower starting torque, and plain split-phase motors suit easily started loads.

Source: All About Circuits: Single-phase Induction Motors.

Answer: A. 100%

Wet-bulb temperature is the lowest temperature you can reach by evaporating water into the air. If the wet bulb doesn't cool below the dry bulb, no net evaporation is happening, which means the air is saturated: 100% RH. Dry air at 0% RH or partly saturated air at 50% RH would have a wet-bulb depression under these conditions. You don't need a chart when the properly obtained readings match.

Sources: NOAA National Weather Service glossary: wet-bulb temperature · NOAA National Weather Service glossary: relative humidity.

Answer: C. Don't use oxygen; get dry nitrogen

OSHA says a jet of oxygen must never strike an oily surface, and refrigeration lines and fittings can carry oil. Oxygen with oil is a fire and explosion hazard, and low pressure, evacuating afterward, or an open far end don't remove it. The CDA handbook describes displacing oxygen with an inert purge during brazing. Follow the specified nitrogen procedure rather than substituting oxygen.

Sources: OSHA 29 CFR 1910.253 · Copper Development Association, Copper Tube Handbook: Purging.

Answer: D. Shaded-pole motor

Shaded-pole motors produce minimal starting torque and are common in small fans. A capacitor-start motor has a capacitor and high starting torque. A three-phase motor needs a three-phase supply, and an ECM has electronic controls.

Source: All About Circuits: Other Specialized Motors — Shaded Pole Induction Motor.

Answer: C. Windows, skylights, and glazed doors in the building envelope

Windows, skylights, and exterior doors are fenestration products; the glazed openings in choice C are examples. They affect heat gain and loss through the building envelope. Roof framing, foundation vents, and interior partition walls are not the fenestration products named here.

Source: National Fenestration Rating Council: About NFRC — windows, doors and skylights.

Answer: D. Fix the leak and dry the area, as well as cleaning up the mold

EPA's point is simple: the key to mold control is moisture control. Clean it up but don't fix the water problem, and the mold will most likely come back. To help prevent growth, wet materials should be dried within 24 to 48 hours. Porous materials with established mold, such as drywall, may need removal and replacement; drying does not by itself clean away existing mold. A thermostat change or a filter doesn't stop water from a leak.

Source: EPA: A Brief Guide to Mold, Moisture and Your Home.

Answer: C. 134.7 psia

Absolute = gauge + atmospheric = 120 + 14.7 = 134.7 psia. Gauges read relative to the atmosphere. 105.3 subtracts, 120 just repeats the gauge reading, and 147 is a decimal slip.

Source: OpenStax College Physics 2e, 11.6 Gauge Pressure, Absolute Pressure.

Answer: A. Swap any two of the three line leads

Interchanging any two of the three line leads reverses the phase rotation and the motor's direction. Moving all three over one position keeps the same sequence, so it still runs backward. Never use the ground as a circuit conductor, and backward rotation alone is not a reason to replace the motor.

Sources: Basic Motor Control (BCcampus): Forward/Reverse Control Circuits · OSHA 29 CFR 1910.333(b)(2): de-energizing, lockout/tagout and verification.

Answer: B. Annealed (soft) tube

Use annealed (soft) tube for flaring. The CDA handbook recommends this temper for Type K or L and says hard tube usually needs its end annealed first. 'Any temper' and 'only rigid Type M' do not match that recommendation; tool and tube instructions still govern.

Source: Copper Development Association, Copper Tube Handbook, 2010 text copy, p. 52: Flared Joints.

Answer: B. 25°C

°C = 5/9 × (°F − 32) = 5/9 × 45 = 25°C. Subtract 32 first. 10.8 multiplies by 5/9 before subtracting, 42.8 forgets to subtract 32, and 45 forgets the 5/9.

Source: OpenStax College Physics 2e, 13.1 Temperature.

Answer: D. The air is oxygen-deficient; do not enter and follow the employer's permit-space procedure

OSHA defines an oxygen-deficient atmosphere as less than 19.5% oxygen, and 18.8% is below that. It is not normal or oxygen-enriched air, and working quickly does not make entry safe. Ventilation and a later acceptable oxygen reading alone do not authorize entry: the applicable permit-space procedure must address all hazards and entry conditions.

Source: OSHA 29 CFR 1910.146, definitions.

Answer: B. A centrifugal switch

A centrifugal switch opens the auxiliary winding at about three-quarters of synchronous speed. A plain split-phase motor has no run capacitor. The overload is a protective device, not the normal start-winding switch, and the contactor controls the whole motor.

Source: All About Circuits: Single-phase Induction Motors.

Answer: D. At least MERV 13, or the highest rating the fan and filter slot can handle

EPA recommends at least MERV 13, or as high as the system's fan and filter slot can accommodate, and says to check with an HVAC technician. MERV means minimum efficiency reporting value. Higher ratings capture more small particles; the filter still has to be compatible with the system. MERV 1 to 4 captures less. 'Washable' describes maintenance, not a guaranteed filtration rating, and removing the filter does not meet the goal.

Source: EPA: Guide to Air Cleaners in the Home.

Answer: D. A brushless DC, permanent-magnet motor with electronic controls that can vary its speed to match the load

ECMs (electronically commutated motors) are brushless DC motors with permanent magnets and electronic controls. Their speed-control behavior depends on the motor design and programming; electronic commutation does not guarantee the same airflow response in every model. The other choices describe split-phase, shaded-pole, and three-phase induction designs.

Source: PNNL Building America Solution Center: ECM Air Handler Fans.

Answer: B. 45°

The handbook describes a common 45° flare. The tool, tube and fitting must match; 30°, 60° and 90° are not that flare. Do not treat every flare connection as interchangeable.

Source: Copper Development Association, Copper Tube Handbook, 2010 text copy, p. 52: Flared Joints.

Answer: B. A ground-fault circuit interrupter (GFCI)

Under the GFCI option, an approved ground-fault circuit interrupter protects this covered temporary receptacle. It detects an imbalance between outgoing and returning current and trips to reduce shock risk. An arc-fault breaker, surge protector or 30-A fuse is not a substitute for that function. OSHA 1926.404(b)(1)(i) also permits a qualifying assured equipment-grounding-conductor program; this question explicitly uses the GFCI option.

Source: OSHA 29 CFR 1926.404(b)(1)(ii).

Answer: C. 4.5 ft

Check both parts and use the larger. Rule one: at least 3 ft. Rule two: the ridge within 10 ft is 2.5 ft up, plus 2 ft = 4.5 ft. So 4.5 ft governs. 2 ft ignores the ridge height, 3 ft stops at the first rule, and 5 ft overshoots the minimum. These are the supplied project requirements for the exercise, not a determination of the code or listing requirements at a real jobsite.

Calculation: derived from the inputs stated in this question.

Answer: B. Isolate and lock out power, safely release stored energy, and have a qualified worker verify the circuit is de-energized

Resistance is measured on a verified de-energized circuit, with hazardous stored energy controlled, including capacitor charge. Follow the equipment and meter instructions; stored charge can injure the worker as well as damage the meter or give false readings. The ohms function needs no line power, the amps setting is the wrong function, and jumpering an overload defeats a safety device.

Sources: Fluke: How to Measure Resistance with a Digital Multimeter · OSHA 29 CFR 1910.333(b)(2): electrical safe-work practices.

Answer: B. 5:1

For an ideal transformer, the voltage ratio equals the turns ratio: 120 / 24 = 5, so 5:1. 1:5 would be a step-up transformer. 10:1 is the ratio for a 240-V primary, not 120 V. 96:1 comes from subtracting the voltages.

Source: OpenStax College Physics 2e, 23.7 Transformers.

Answer: C. Remove the source: get the paint cans out

EPA says eliminating individual pollution sources or reducing their emissions is usually the most effective way to improve indoor air, and it's often cheaper than more ventilation. Running the blower just moves the fumes around, a filter rated for particles isn't the fix for a source you can simply remove, and a freshener adds another chemical.

Source: EPA: Improving Indoor Air Quality.

Answer: C. Conduction

Conduction is heat transfer through stationary matter by physical contact, which is what happens through a solid tube wall. Convection moves heat by fluid motion, like air flowing across the coil. Radiation is electromagnetic, and evaporation is a phase change, not a transfer method through metal.

Source: OpenStax College Physics 2e, 14.4 Heat Transfer Methods.

Answer: B. The currents flow in opposite directions and cancel; clamp only one conductor

Currents flowing in opposite directions cancel inside the clamp. Put just one conductor in the jaws. The near-zero result is the net current through the jaws, not evidence of zero motor current. True-RMS matters for distorted waveforms, not for this.

Sources: Fluke: How to Measure Current with a Clamp Meter · Fluke: Leakage Current Measurement Basics — magnetic-field cancellation paragraph.

Answer: B. Let the wheel stop and restrain it, or otherwise make the stored energy safe, before reaching in

OSHA requires that after lockout, all potentially hazardous stored or residual energy be relieved, disconnected, restrained, and otherwise rendered safe. A coasting wheel is stored energy. Locking out the power doesn't stop it, and a tag is only a warning device with no physical restraint. Grabbing a moving belt is the injury you're trying to prevent. The energy-control procedure must also prevent hazardous restart or reaccumulation and verify isolation before work.

Source: OSHA 29 CFR 1910.147.

Answer: A. 6 1/4 in

Subtract the starting mark: 7 1/4 − 1 = 6 1/4 in. 7 1/4 reads the end mark as if you started at zero, 8 1/4 adds the inch instead of subtracting it, and 6 in drops the fraction.

Calculation: derived from the inputs stated in this question.

Answer: B. Apply suitable non-reflective tape, let it reach tube temperature, and measure it with the correct emissivity setting and spot size

Bare shiny metal has low emissivity, which can make its infrared reading misleading. A temperature-suitable, non-reflective patch that has reached the tube temperature and fills the measurement spot gives a better target; use the instrument's specified emissivity setting for that surface. Standing back makes the measured spot bigger so it picks up surroundings. Adding a guessed number isn't a measurement, and insulation is a different surface at a different temperature.

Source: Fluke: How to Get Great Results with an Infrared Thermometer.

Answer: A. Don't alter the truss: reroute the duct, or get an approved repair from a registered design professional

The specified approval requirement rules out cutting, notching or drilling the web on your own. Reroute the duct or obtain the approved alteration design before work; an improvised 2x4 patch is not that approval. A one-third-depth shortcut does not override the truss requirement. Jersey County's 2018-IRC-based guide illustrates this restriction; this exercise does not establish which code applies at another jobsite.

Source: Jersey County Code Administrator, Residential Building Guide, p. 2: Roof/Ceiling Construction (2018 IRC basis).

Answer: A. A true-RMS meter

Use true-RMS measurement for the effective value of distorted AC current, within the meter's specified limits. An average-responding meter calibrated for a sine wave can give the wrong value on a nonsinusoidal waveform. The two types do not agree on every waveform, and a voltmeter does not measure current. A true-RMS label alone does not establish suitability for every drive-output signal.

Source: Fluke: What is True-RMS?.

Answer: C. ASHRAE 62.2

ASHRAE 62.2 addresses ventilation and acceptable indoor air quality in residential buildings, including dwelling-unit ventilation and local exhaust. Its 2025 scope includes dwelling units with nontransient occupants; it is not a blanket rule for every transient lodging space. OSHA 1910.147 concerns hazardous-energy control, OSHA 1926.1053 concerns ladders, and SAE J533 is not the residential ventilation standard.

Source: ASHRAE: Standards 62.1 and 62.2 — 2025 residential standard description.