TOP 30
1. What is the First Law of Thermodynamics?
→ It states that energy can neither be created nor destroyed, only transferred or
converted. In equation form:
ΔQ = ΔU + ΔW
where Q = heat added, U = internal energy, W = work done.
2. Explain the difference between heat and work.
→ Heat is energy transfer due to temperature difference; work is energy transfer due
to force acting through a distance.
3. What is entropy?
→ Entropy is a measure of randomness or disorder in a system. It increases in
irreversible processes.
4. What are the different types of heat exchangers?
→ Shell and tube, plate type, finned tube, regenerative, and double-pipe exchangers.
5. What is the difference between a closed and open system?
→ Closed system: mass remains constant; only energy can cross the boundary.
Open system: both mass and energy can cross.
6. Explain the working of a four-stroke engine.
→ Intake → Compression → Power → Exhaust.
7. What is the difference between SI and CI engines?
→ SI (Spark Ignition): Uses spark plug and petrol.
CI (Compression Ignition): Uses compression and diesel.
8. Define Refrigeration Cycle.
→ A reversed Rankine cycle: evaporation → compression → condensation →
expansion.
9. What is the difference between laminar and turbulent flow?
→ Laminar: Smooth, orderly (Re < 2000).
Turbulent: Chaotic, high velocity (Re > 4000).
10. What is Bernoulli’s Principle?
→ In steady, incompressible flow with no friction, the total mechanical energy is
conserved.
P + ½ρv² + ρgh = constant.
DESIGN AND MANUFACTURING QUESTIONS
11. What is the difference between stress and strain?
→ Stress = Force/Area; Strain = Change in Length/Original Length.
12. What is the factor of safety (FOS)?
→ It is the ratio of the material's strength to the actual load.
FOS = Ultimate Stress / Working Stress.
13. What are the types of fits?
→ Clearance fit, interference fit, and transition fit.
14. What is tolerancing?
→ It defines the acceptable variation in dimensions for manufacturing.
15. Differentiate between CNC and conventional machines.
→ CNC: Computer-controlled, precise, automated.
Conventional: Manually operated.
16. What is the principle of welding?
→ Welding joins materials by heating to melting point and adding filler if needed.
17. What is casting and its types?
→ Casting is pouring molten metal into a mold. Types: Sand, die, investment, and
centrifugal casting.
18. Define forging.
→ Forging is shaping metal using compressive forces, usually when hot.
19. What is the purpose of heat treatment?
→ To alter physical and mechanical properties like hardness, toughness, and ductility.
20. What is the difference between rolling and extrusion?
→ Rolling: Material passed through rollers.
Extrusion: Material forced through a die.
AUTOMATION, CONTROL & MECHATRONICS QUESTIONS
21. What is the PID controller?
→ A control loop mechanism:
P: Proportional
I: Integral
D: Derivative
Used in feedback systems.
22. What is the use of a sensor in automation?
→ Sensors detect physical changes (temperature, pressure, position) and send data for
control.
23. What are the advantages of CAD/CAM?
→ Higher accuracy, better visualization, reduced prototyping cost, and faster design
modifications.
24. What is the role of PLC in automation?
→ PLC (Programmable Logic Controller) is used to automate machinery and
processes.
25. What is mechatronics?
→ Integration of mechanical, electronics, computer, and control systems for advanced
automation.
GENERAL HR & SITUATIONAL QUESTIONS
26. Tell me about yourself.
→ Start with your name, education, technical skills, internships, and career goals.
27. Why did you choose mechanical engineering?
→ Discuss your interest in machines, design, manufacturing, or energy systems.
28. What are your strengths and weaknesses?
→ Strength: Analytical thinking, teamwork, etc.
Weakness: Perfectionism, but improving through time management.
29. Where do you see yourself in 5 years?
→ In a core technical role contributing to innovative projects or pursuing a higher
position with leadership responsibilities.
30. Why should we hire you?
→ Mention your technical skills, adaptability, willingness to learn, and alignment
with the company’s goals.
