General Engineering Science
General Engineering Science tests common fundamentals that cut across civil, mechanical, and electrical branches: units and dimensions, engineering mechanics, material properties, basic thermodynamics, fluid statics, electrical quantities, and simple drawing conventions.
Core rules and concepts
- SI units: length metre, mass kilogram, time second, force newton (kg·m/s²), pressure pascal (N/m²), power watt (J/s). Convert consistently before calculating.
- Dimensional homogeneity: every term in a valid equation has the same dimensions; use it to check formulae.
- Mechanics: resolve forces, draw free-body diagrams, and apply ΣF = 0 and ΣM = 0 for statics; distinguish mass from weight.
- Thermodynamics: absolute pressure = gauge pressure + atmospheric pressure; absolute temperature in kelvin = °C + 273.15. For a reversible cycle, efficiency depends on absolute temperatures.
- Materials: stress = force/area; strain = change in length/original length; Young's modulus = stress/strain in the elastic range.
Worked example
A 20 kN load hangs from a 10 mm diameter steel rod. Find the tensile stress. Area = πd²/4 = π(0.010 m)²/4 = 7.854 × 10⁻⁵ m². Stress = 20,000 N / 7.854 × 10⁻⁵ m² = 2.55 × 10⁸ Pa ≈ 255 MPa. The reasoning matters: convert mm to m and kN to N before dividing.
Traps
Mixing gauge and absolute pressure is the most common error. Using diameter instead of radius in area, or forgetting the square, changes the answer by a factor of four. In trusses, a member carrying zero force can still be present; do not assume all members are stressed. In unit conversion, write the conversion factor as a fraction so units cancel.