AIT Trade Theory 4 — Questions and Answers
Question 1: In HVAC theory, what is the refrigeration cycle process called when a refrigerant absorbs heat and changes from a liquid to a vapor?
- Condensation
- Compression
- Evaporation (Correct answer)
- Expansion
Correct answer: Evaporation
Evaporation occurs in the evaporator coil where the low-pressure liquid refrigerant absorbs heat from the surrounding air or fluid, causing it to vaporize and cool the space.
Question 2: What is the purpose of a P-trap installed under a sink drain?
- To increase water pressure at the faucet
- To hold water that acts as a seal against sewer gases entering the building (Correct answer)
- To filter debris and prevent drain clogs
- To regulate water flow to the drain
Correct answer: To hold water that acts as a seal against sewer gases entering the building
The curved P-trap holds a small amount of water that creates a water seal, preventing toxic and odorous sewer gases from traveling back up through the drain into the living space.
Question 3: What is the recommended practice when working near overhead power lines?
- Maintain a minimum safe distance as required by safety regulations (Correct answer)
- Use wooden ladders only and proceed carefully
- Work at night when the lines are de-energized
- Wear rubber-soled shoes and proceed without restriction
Correct answer: Maintain a minimum safe distance as required by safety regulations
Safety regulations require workers and equipment to maintain a minimum safe approach distance from overhead power lines, which varies based on line voltage and must be determined before work begins.
Question 4: In metalworking, what is the purpose of using a cutting fluid or coolant during machining operations?
- To increase the hardness of the metal being cut
- To reduce friction and heat while improving surface finish and tool life (Correct answer)
- To prevent sparks from igniting flammable materials
- To lubricate the machine's internal gears and bearings
Correct answer: To reduce friction and heat while improving surface finish and tool life
Cutting fluids reduce friction and heat generated during machining, which extends tool life, improves dimensional accuracy, removes chips from the cutting zone, and produces a better surface finish.
Question 5: What does the acronym WHMIS stand for in Canadian and North American workplace safety?
- Workplace Hazardous Materials Information System (Correct answer)
- Worker Health Management and Inspection Standards
- Workplace Handling of Materials in Industrial Settings
- Written Hazard Management and Inspection System
Correct answer: Workplace Hazardous Materials Information System
WHMIS stands for Workplace Hazardous Materials Information System, which is a Canada-wide system designed to provide employers and employees with important information about hazardous products used in the workplace.
Question 6: What is the function of a ground fault circuit interrupter (GFCI) outlet?
- To protect against overloads by tripping the main breaker
- To detect current imbalances between hot and neutral conductors and quickly cut power (Correct answer)
- To step down voltage from 240V to 120V for appliances
- To prevent power surges from reaching connected devices
Correct answer: To detect current imbalances between hot and neutral conductors and quickly cut power
A GFCI detects even small current imbalances between the hot and neutral wires (indicating current is flowing through an unintended path such as a person) and interrupts power within milliseconds to prevent electrocution.
Question 7: When laying out work using a plumb bob, what reference does it establish?
- A perfectly level horizontal line
- A precise true vertical (plumb) line using gravity (Correct answer)
- A 45-degree angle reference for mitered cuts
- A fixed measurement reference point for layout work
Correct answer: A precise true vertical (plumb) line using gravity
A plumb bob uses the force of gravity to establish a perfectly vertical (plumb) reference line, which is essential for aligning walls, columns, and other vertical structural elements.
AIT Trade Theory 4
In HVAC theory, what is the refrigeration cycle process called when a refrigerant absorbs heat and changes from a liquid to a vapor?