Principles and Practice of Engineering (PE) Mechanical HVAC and Refrigeration Exam

Principles and Practice of Engineering
(PE) Mechanical HVAC and
Refrigeration Exam
Question 1. Which law states that energy cannot be created or

destroyed, only transformed?


A) First Law of Thermodynamics


B) Second Law of Thermodynamics


C) Zeroth Law of Thermodynamics


D) Boyle’s Law


Answer: A


Explanation: The First Law of Thermodynamics is the principle of

conservation of energy.




Question 2. What does the Second Law of Thermodynamics primarily

address?

,Principles and Practice of Engineering
(PE) Mechanical HVAC and
Refrigeration Exam
A) Conservation of mass


B) Increase of entropy


C) Conservation of momentum


D) Constant temperature


Answer: B


Explanation: The Second Law states entropy of a closed system will not

decrease, indicating the direction of natural processes.




Question 3. Which property measures the disorder or randomness in a

system?


A) Enthalpy


B) Entropy

,Principles and Practice of Engineering
(PE) Mechanical HVAC and
Refrigeration Exam
C) Pressure


D) Temperature


Answer: B


Explanation: Entropy is a measure of system disorder.




Question 4. Which variable is held constant in an isobaric process?


A) Volume


B) Pressure


C) Temperature


D) Entropy


Answer: B

, Principles and Practice of Engineering
(PE) Mechanical HVAC and
Refrigeration Exam
Explanation: Isobaric means constant pressure.




Question 5. In a psychrometric chart, what does the horizontal axis

typically represent?


A) Dry-bulb temperature


B) Wet-bulb temperature


C) Relative humidity


D) Enthalpy


Answer: A


Explanation: The x-axis on a psychrometric chart is dry-bulb

temperature.