Principles and Practice of Engineering (PE) Mechanical
Examination Questions And Correct Answers (Verified
Answers) Plus Rationales 2025/2026 Q&A | Instant
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1. In thermodynamics, the First Law for a closed system is expressed as:
A. ΔU = Q + W
B. ΔU = Q − W
C. ΔU = W − Q
D. ΔU = Q / W
Answer: B
Rationale: The First Law states that change in internal energy equals heat
added to the system minus work done by the system.
2. The efficiency of a Carnot engine depends on:
A. Working fluid
B. Pressure ratio
C. Temperature limits
D. Heat input
Answer: C
Rationale: Carnot efficiency depends only on the absolute temperatures of the
hot and cold reservoirs.
3. For incompressible steady flow, the continuity equation reduces to:
A. A₁V₁ = A₂V₂
B. P₁V₁ = P₂V₂
C. ṁ₁ = 0
D. ρ₁V₁ = ρ₂V₂
Answer: A
Rationale: For incompressible flow, density is constant, so volumetric flow rate
is conserved.
,4. Reynolds number primarily indicates:
A. Heat transfer rate
B. Flow regime
C. Pressure drop
D. Viscosity
Answer: B
Rationale: Reynolds number predicts whether flow is laminar or turbulent.
5. The unit of thermal conductivity in SI is:
A. W/m·K
B. W/K
C. J/kg·K
D. N·m
Answer: A
Rationale: Thermal conductivity measures heat transfer per unit length and
temperature gradient.
6. In conduction through a plane wall, heat transfer rate is proportional to:
A. Thickness
B. Thermal resistance
C. Temperature difference
D. Density
Answer: C
Rationale: From Fourier’s law, heat transfer is proportional to temperature
difference.
7. The modulus of elasticity is defined as:
A. Stress / Strain
B. Strain / Stress
, C. Load / Area
D. Force / Length
Answer: A
Rationale: Young’s modulus equals stress divided by strain in the elastic region.
8. A simply supported beam with a center load has maximum moment at:
A. Support
B. Quarter span
C. Midspan
D. Uniform everywhere
Answer: C
Rationale: Maximum bending moment occurs at midspan under a center load.
9. The Brayton cycle is associated with:
A. Steam turbines
B. Gas turbines
C. Refrigeration
D. Diesel engines
Answer: B
Rationale: The Brayton cycle describes ideal gas turbine operation.
10. Specific heat at constant pressure is greater than at constant volume
because:
A. Work is done during expansion
B. Temperature is constant
C. Volume decreases
D. Entropy decreases
Answer: A
Rationale: At constant pressure, added heat performs boundary work in
addition to raising internal energy.
Examination Questions And Correct Answers (Verified
Answers) Plus Rationales 2025/2026 Q&A | Instant
Download Pdf
1. In thermodynamics, the First Law for a closed system is expressed as:
A. ΔU = Q + W
B. ΔU = Q − W
C. ΔU = W − Q
D. ΔU = Q / W
Answer: B
Rationale: The First Law states that change in internal energy equals heat
added to the system minus work done by the system.
2. The efficiency of a Carnot engine depends on:
A. Working fluid
B. Pressure ratio
C. Temperature limits
D. Heat input
Answer: C
Rationale: Carnot efficiency depends only on the absolute temperatures of the
hot and cold reservoirs.
3. For incompressible steady flow, the continuity equation reduces to:
A. A₁V₁ = A₂V₂
B. P₁V₁ = P₂V₂
C. ṁ₁ = 0
D. ρ₁V₁ = ρ₂V₂
Answer: A
Rationale: For incompressible flow, density is constant, so volumetric flow rate
is conserved.
,4. Reynolds number primarily indicates:
A. Heat transfer rate
B. Flow regime
C. Pressure drop
D. Viscosity
Answer: B
Rationale: Reynolds number predicts whether flow is laminar or turbulent.
5. The unit of thermal conductivity in SI is:
A. W/m·K
B. W/K
C. J/kg·K
D. N·m
Answer: A
Rationale: Thermal conductivity measures heat transfer per unit length and
temperature gradient.
6. In conduction through a plane wall, heat transfer rate is proportional to:
A. Thickness
B. Thermal resistance
C. Temperature difference
D. Density
Answer: C
Rationale: From Fourier’s law, heat transfer is proportional to temperature
difference.
7. The modulus of elasticity is defined as:
A. Stress / Strain
B. Strain / Stress
, C. Load / Area
D. Force / Length
Answer: A
Rationale: Young’s modulus equals stress divided by strain in the elastic region.
8. A simply supported beam with a center load has maximum moment at:
A. Support
B. Quarter span
C. Midspan
D. Uniform everywhere
Answer: C
Rationale: Maximum bending moment occurs at midspan under a center load.
9. The Brayton cycle is associated with:
A. Steam turbines
B. Gas turbines
C. Refrigeration
D. Diesel engines
Answer: B
Rationale: The Brayton cycle describes ideal gas turbine operation.
10. Specific heat at constant pressure is greater than at constant volume
because:
A. Work is done during expansion
B. Temperature is constant
C. Volume decreases
D. Entropy decreases
Answer: A
Rationale: At constant pressure, added heat performs boundary work in
addition to raising internal energy.
