Engineering Disciplines
What this domain tests
Engineering Disciplines covers the core of the branch you choose - mechanical, chemical, electrical, electronics, instrumentation, civil, computer or metallurgical. Across branches, BARC expects conservation laws, unit-consistent calculations and the ability to connect a formula to a physical component.
Shared fundamentals
- Mass balance: at steady state, Σṁ_in = Σṁ_out. Energy balance: Q − W = ΔH + ΔKE + ΔPE.
- Fluid flow: Re = ρVD/μ; laminar below about 2000, turbulent above about 4000; Bernoulli applies with head loss h_L.
- Solids: σ = F/A, ε = ΔL/L, E = σ/ε; bending stress σ = My/I.
- Electrical: V = IR, P = VI; three-phase P = √3 V_L I_L cosφ.
- Instrumentation: accuracy versus precision; span and zero; calibration traceability.
Worked example
Water flows at ṁ = 2 kg/s and is heated from 20 °C to 80 °C. Take Cp = 4.18 kJ kg^-1 K^-1. Then Q = ṁCpΔT = 2 × 4.18 × 60 = 501.6 kW. The reasoning is steady flow with no shaft work and negligible kinetic and potential changes, so the enthalpy rise equals the heat input. If the answer is requested in watts, multiply by 1000: 5.016 × 10^5 W.
Traps
- Mixing gauge and absolute pressure.
- Using diameter where radius is needed (area = πd²/4).
- Forgetting unit conversions: kJ versus J, min versus s, bar versus Pa.
- Wrong sign for work done by versus on the system.
- Treating a transient process as steady state.