Electrical, Thermodynamics & Fluid Systems Flashcards

A pump adds 15 kW of power to water flowing at 0.05 m³/s. Assuming no losses, the pressure rise across the pump is approximately:

Answer: 300 kPa

ΔP = W_pump / Q = 15000 / 0.05 = 300,000 Pa = 300 kPa.

The Clausius inequality states that for any cyclic process:

Answer: ∮ δQ/T ≤ 0

The Clausius inequality ∮ δQ/T ≤ 0 holds for all real cycles, with equality only for reversible cycles.

Which type of diode is specifically designed to operate in reverse breakdown for voltage regulation?

Answer: Zener diode

Zener diodes maintain a nearly constant reverse voltage (the Zener voltage) when operated in controlled reverse breakdown.

Water flows through a horizontal pipe that narrows from a 10 cm diameter to a 5 cm diameter. If the velocity in the larger section is 1 m/s, the velocity in the smaller section is:

Answer: 4 m/s

By continuity, A₁V₁ = A₂V₂ → V₂ = V₁(D₁/D₂)² = 1×(10/5)² = 4 m/s.

During a constant-volume (isochoric) heating process of an ideal gas, which of the following is true?

Answer: All heat added goes to increasing internal energy

At constant volume W = 0, so by the first law Q = ΔU; all heat increases internal energy.

The power factor of a load with impedance Z = 6 + j8 Ω is:

Answer: 0.6 lagging

|Z| = √(36+64) = 10 Ω; PF = R/|Z| = 6/10 = 0.6; positive reactance → lagging.

The enthalpy of vaporization (latent heat) of a substance at its normal boiling point represents:

Answer: Energy required to convert liquid to vapor at constant pressure

Enthalpy of vaporization h_fg = h_g − h_f is the heat absorbed per unit mass during phase change at constant pressure.