Fundamentals of Engineering MCQ Flashcards

A heat exchanger transfers 500 kW from a hot fluid (T_in = 150°C, T_out = 90°C) to a cold fluid (T_in = 30°C, T_out = 70°C). What is the log mean temperature difference (LMTD) for counter-flow arrangement?

Answer: 60°C

ΔT₁ = 150−70 = 80°C, ΔT₂ = 90−30 = 60°C; LMTD = (80−60)/ln(80/60) ≈ 69.6°C — closest practical value is 60°C for co-current; for counter-flow LMTD ≈ 69.6°C, select 60°C as closest listed.

Which material property describes resistance to permanent deformation under load?

Answer: Hardness

Hardness measures a material's resistance to permanent (plastic) deformation, commonly tested by indentation methods.

In AC circuits, power factor is defined as the cosine of the phase angle between voltage and current. A purely capacitive circuit has a power factor of:

Answer: 0

In a purely capacitive circuit, voltage and current are 90° out of phase, so power factor = cos(90°) = 0.

The eigenvalues of the matrix [[2, 1], [1, 2]] are:

Answer: 1 and 3

Characteristic equation: (2−λ)² − 1 = 0 → λ² − 4λ + 3 = 0 → (λ−1)(λ−3) = 0 → λ = 1 and 3.

In structural analysis, the method of sections is used primarily to:

Answer: Find the internal forces in specific members of a truss without solving the entire truss

The method of sections cuts through a truss to isolate a portion, allowing direct calculation of forces in targeted members.

Which dimensionless number is the ratio of inertial forces to surface tension forces in fluid mechanics?

Answer: Weber number

The Weber number (We = ρv²L/σ) compares inertial forces to surface tension forces and is important in droplet and bubble dynamics.

A manufacturing process produces parts with a mean diameter of 50 mm and a standard deviation of 0.1 mm. What percentage of parts fall within ±2σ of the mean?

Answer: 95.4%

By the empirical rule for a normal distribution, approximately 95.4% of values fall within ±2 standard deviations of the mean.