BT-203 Basic Mechanical Engineering - Dec 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aDefine alloy steel. Explain the effect of alloying elements on steel properties.
   How to answer

   • Definition of alloy steel as carbon steel with added alloying elements
   • List common alloying elements - Cr, Ni, Mo, Mn, V, W, etc.
   • Effect of each element on hardness, strength, corrosion resistance, hardenability
   • Examples of properties improvement and applications
2. 7 Marks
   bDescribe important phases and critical points in the Iron-Carbon diagram with the help of sketch.
   How to answer

   • Neat sketch of Iron-Carbon equilibrium diagram with axes temperature vs %C
   • Mark important phases: ferrite, austenite, cementite, pearlite, martensite, ledeburite
   • Mark critical points: eutectoid, eutectic, peritectic temperatures and compositions
   • Brief significance of each phase and point
3. 7 Marks
   aDefine lathe. Explain the main parts of a lathe machine with neat sketch.
   How to answer

   • Definition of lathe as machine tool for turning
   • Neat labelled sketch showing bed, headstock, tailstock, carriage, chuck
   • Function of each main part
   • Material removal principle in brief
4. 7 Marks
   bList the different types of temperature measuring instruments. Also explain the working of optical pyrometer.
   How to answer

   • List temperature measuring instruments: thermometers, thermocouples, RTDs, pyrometers
   • Classification contact vs non-contact type
   • Construction and working principle of optical pyrometer
   • Applications and advantages
5. 7 Marks
   aDerive Bernoulli's equation for incompressible fluids. Also discuss its physical significance.
   How to answer

   • State assumptions: steady, incompressible, inviscid flow along streamline
   • Apply energy conservation / Euler equation integration
   • Derive $p/\rho g + V^2/2g + z = constant$
   • Explain pressure, velocity and datum heads and physical significance
6. 7 Marks
   bExplain the construction and working principle of a reciprocating pump.
   How to answer

   • Definition and classification of reciprocating pump
   • Construction: cylinder, piston, suction and delivery valves
   • Working: suction stroke and delivery stroke with neat sketch
   • Applications and characteristics
7. 7 Marks
   aDefine draught. Explain natural draught and its working.
   How to answer

   • Definition of draught as pressure difference for flue gas flow
   • Definition of natural draught using chimney effect
   • Working: hot gas density difference creating suction
   • Advantages, disadvantages and formula in brief
8. 7 Marks
   bDefine the following Statements of second law of thermodynamics. (i)) Clausius statement (ii)) Kelvin-Plank statement.
   How to answer

   • State Clausius statement: heat cannot flow cold to hot without external work
   • State Kelvin-Planck statement: impossible to convert all heat to work cyclically
   • Significance in defining second law and irreversibility
   • Equivalence of the two statements in brief
9. 7 Marks
   aExplain the Diesel cycle with $P-V$ and $T-S$ diagram. Also Derive the efficiency of the Diesel cycle.
   How to answer

   • Air-standard Diesel cycle processes: isentropic compression, constant pressure heat addition, isentropic expansion, constant volume heat rejection
   • Neat $P-V$ and $T-S$ diagrams with labelling
   • Derivation steps using cut-off ratio and compression ratio
   • Final efficiency expression $\eta = 1 - (1/r^{\gamma-1})[(\rho^{\gamma}-1)/\gamma(\rho-1)]$
10. 7 Marks
    bExplain the working of a four-stroke petrol engine with neat sketch.
    How to answer

    • Neat sketch of four-stroke petrol engine components
    • Four strokes: suction, compression, power, exhaust
    • Role of spark plug, valves and piston movement
    • Cycle of operations and applications
11. 7 Marks
    aDescribe tensile testing and explain stress-strain diagram of ductile materials.
    How to answer

    • Procedure of tensile test with universal testing machine and specimen
    • Neat stress-strain curve for ductile material
    • Mark proportional limit, yield point, ultimate strength, fracture
    • Explain elastic, plastic, necking regions
12. 7 Marks
    bDefine compressor. Explain the working principle of a reciprocating air compressor.
    How to answer

    • Definition of compressor as device to increase air pressure
    • Construction of reciprocating air compressor: cylinder, piston, valves
    • Working principle: suction, compression and delivery
    • Applications and types in brief
13. 7 Marks
    aDefine boiler. Explain the classification of boilers also explain any one of them.
    How to answer

    • Definition of boiler as steam generating device
    • Classification: fire-tube vs water-tube, horizontal/vertical, etc.
    • Detailed explanation of any one boiler with sketch
    • Applications and safety in brief
14. 7 Marks
    bExplain the following- (i)) Homogeneous and heterogeneous fluids (ii)) Newton's law of viscosity
    How to answer

    • Define homogeneous vs heterogeneous fluids with examples
    • State Newton's law of viscosity $\tau = \mu du/dy$
    • Explain terms: shear stress, velocity gradient, viscosity
    • Examples of Newtonian and non-Newtonian fluids
15. 7 Marks
    aExplain the construction and working principle of a dial gauge with its applications.
    How to answer

    • Construction: plunger, dial, gear train, pointer
    • Working principle: linear displacement to rotary pointer motion
    • Neat sketch and least count concept
    • Applications in alignment, run-out, flatness measurement
16. 7 Marks
    bDefine modulus of elasticity. Explain Young's modulus, bulk modulus and shear modulus.
    How to answer

    • Define modulus of elasticity as stress/strain ratio
    • Young's modulus for axial loading $E=\sigma/\epsilon$
    • Bulk modulus $K$ and shear modulus $G$ definitions and formulas
    • Relation between elastic constants and units