Louisiana 640-LA Second Class
Stationary Air Conditioning Contractor
Exam
Complete Practice Examination
1. Which of the following best describes "sensible heat" in an air conditioning context?
A. The heat required to change water to vapor
B. The heat associated with a change in temperature of a substance without a phase change
C. The heat associated with moisture in the air
D. The heat required to cool the refrigerant below saturation temperature
Correct Answer: B
Explanation: Sensible heat is the heat added or removed that changes the temperature of a substance
but does not cause a phase change (e.g., from liquid to vapor) .
2. In air conditioning terminology, "latent heat" refers to:
A. Heat that directly raises the temperature of a substance
B. Heat required to induce a phase change without a temperature change
C. Additional heat from solar radiation
D. Heat lost through uninsulated ducts
Correct Answer: B
Explanation: Latent heat is the heat that causes a change in phase (solid to liquid, liquid to gas) without
a change in temperature .
3. The term "BTU" stands for:
A. British Thermal Unit
B. Boiler Temperature Unit
C. Basic Temperature Utility
D. Burn Time Unit
,Correct Answer: A
Explanation: BTU is short for "British Thermal Unit," a standard measure of heat energy. One BTU is the
amount of heat needed to raise the temperature of one pound of water by 1°F .
4. According to basic thermodynamic principles, heat naturally flows:
A. From cold objects to warmer objects
B. From warm objects to colder objects
C. Randomly in all directions
D. Only if driven by a compressor
Correct Answer: B
Explanation: Heat transfer occurs spontaneously from a higher temperature region to a lower
temperature region .
5. Which law of thermodynamics states that energy can neither be created nor destroyed, but can
only change form?
A. Zeroth Law of Thermodynamics
B. First Law of Thermodynamics
C. Second Law of Thermodynamics
D. Third Law of Thermodynamics
Correct Answer: B
Explanation: The First Law of Thermodynamics is the law of conservation of energy, stating that energy
in a closed system remains constant .
6. The "Second Law of Thermodynamics" states:
A. Energy cannot be created or destroyed
B. Heat flows naturally from a colder body to a hotter body
C. The total entropy of an isolated system always increases over time
D. A refrigerant's pressure is proportional to its temperature
Correct Answer: C
Explanation: The Second Law of Thermodynamics involves entropy, indicating the direction of heat flow
(hot to cold) and that the disorder (entropy) in an isolated system cannot decrease spontaneously .
, 7. In HVAC terminology, "ASHRAE" stands for:
A. American Society of Heating, Refrigerating and Air-Conditioning Engineers
B. Association of Systemic Heating and Refrigeration Engineers
C. American Service for Heat and Refrigeration Evaluation
D. Accredited Society of Home Air Regulation Experts
Correct Answer: A
Explanation: ASHRAE is a global society advancing human well-being through sustainable technology for
the built environment, focusing on HVAC/R systems .
8. The psychrometric chart is primarily used to analyze:
A. Electrical conductivity of refrigerants
B. Relationship between air temperature, moisture, and enthalpy
C. Efficiency of compressors in varying pressures
D. Fan performance curves
Correct Answer: B
Explanation: A psychrometric chart helps HVAC professionals understand air properties (temperature,
humidity, enthalpy) to design and analyze systems .
9. When referring to psychrometrics, "relative humidity" is:
A. The absolute humidity expressed in grains per pound of dry air
B. The ratio of the actual water vapor content to the maximum possible at a specific temperature
C. The total moisture content of the air, measured in pounds per hour
D. The moisture content measured at saturation
Correct Answer: B
Explanation: Relative humidity (RH) expresses how close the air is to saturation. At 100% RH, the air is
fully saturated with water vapor at that temperature .
10. The process of removing heat from a space where it is not wanted and transferring it to a place
where it is unobjectionable defines:
A. Refrigeration
B. Air conditioning
Stationary Air Conditioning Contractor
Exam
Complete Practice Examination
1. Which of the following best describes "sensible heat" in an air conditioning context?
A. The heat required to change water to vapor
B. The heat associated with a change in temperature of a substance without a phase change
C. The heat associated with moisture in the air
D. The heat required to cool the refrigerant below saturation temperature
Correct Answer: B
Explanation: Sensible heat is the heat added or removed that changes the temperature of a substance
but does not cause a phase change (e.g., from liquid to vapor) .
2. In air conditioning terminology, "latent heat" refers to:
A. Heat that directly raises the temperature of a substance
B. Heat required to induce a phase change without a temperature change
C. Additional heat from solar radiation
D. Heat lost through uninsulated ducts
Correct Answer: B
Explanation: Latent heat is the heat that causes a change in phase (solid to liquid, liquid to gas) without
a change in temperature .
3. The term "BTU" stands for:
A. British Thermal Unit
B. Boiler Temperature Unit
C. Basic Temperature Utility
D. Burn Time Unit
,Correct Answer: A
Explanation: BTU is short for "British Thermal Unit," a standard measure of heat energy. One BTU is the
amount of heat needed to raise the temperature of one pound of water by 1°F .
4. According to basic thermodynamic principles, heat naturally flows:
A. From cold objects to warmer objects
B. From warm objects to colder objects
C. Randomly in all directions
D. Only if driven by a compressor
Correct Answer: B
Explanation: Heat transfer occurs spontaneously from a higher temperature region to a lower
temperature region .
5. Which law of thermodynamics states that energy can neither be created nor destroyed, but can
only change form?
A. Zeroth Law of Thermodynamics
B. First Law of Thermodynamics
C. Second Law of Thermodynamics
D. Third Law of Thermodynamics
Correct Answer: B
Explanation: The First Law of Thermodynamics is the law of conservation of energy, stating that energy
in a closed system remains constant .
6. The "Second Law of Thermodynamics" states:
A. Energy cannot be created or destroyed
B. Heat flows naturally from a colder body to a hotter body
C. The total entropy of an isolated system always increases over time
D. A refrigerant's pressure is proportional to its temperature
Correct Answer: C
Explanation: The Second Law of Thermodynamics involves entropy, indicating the direction of heat flow
(hot to cold) and that the disorder (entropy) in an isolated system cannot decrease spontaneously .
, 7. In HVAC terminology, "ASHRAE" stands for:
A. American Society of Heating, Refrigerating and Air-Conditioning Engineers
B. Association of Systemic Heating and Refrigeration Engineers
C. American Service for Heat and Refrigeration Evaluation
D. Accredited Society of Home Air Regulation Experts
Correct Answer: A
Explanation: ASHRAE is a global society advancing human well-being through sustainable technology for
the built environment, focusing on HVAC/R systems .
8. The psychrometric chart is primarily used to analyze:
A. Electrical conductivity of refrigerants
B. Relationship between air temperature, moisture, and enthalpy
C. Efficiency of compressors in varying pressures
D. Fan performance curves
Correct Answer: B
Explanation: A psychrometric chart helps HVAC professionals understand air properties (temperature,
humidity, enthalpy) to design and analyze systems .
9. When referring to psychrometrics, "relative humidity" is:
A. The absolute humidity expressed in grains per pound of dry air
B. The ratio of the actual water vapor content to the maximum possible at a specific temperature
C. The total moisture content of the air, measured in pounds per hour
D. The moisture content measured at saturation
Correct Answer: B
Explanation: Relative humidity (RH) expresses how close the air is to saturation. At 100% RH, the air is
fully saturated with water vapor at that temperature .
10. The process of removing heat from a space where it is not wanted and transferring it to a place
where it is unobjectionable defines:
A. Refrigeration
B. Air conditioning
