Mechanical Engineering - MCQ Practice Questions

During throttling of a real gas through an expansion valve, which thermodynamic property remains constant?

In a turbocharger application, compressed air enters a turbine. If the isentropic efficiency of the turbine is 0.85, what does this indicate?

For an ideal gas in a constant pressure (isobaric) process from state 1 to state 2, the change in specific entropy is:

A heat pump operating between 280 K and 350 K has a coefficient of performance (COP) of 5. How much work input is required to transfer 1000 J of heat to the hot reservoir?

Steam at 80 kPa with enthalpy 2660 kJ/kg and entropy 7.31 kJ/kg·K. What is the thermodynamic state of this steam?

An ideal gas expands adiabatically from initial state (P₁=10 bar, V₁=0.5 m³) to final volume V₂=1.5 m³. If γ=1.4, find the final pressure approximately.

For a closed system undergoing a cyclic process, which statement is correct?

The dryness fraction (quality) of steam at a state where specific enthalpy is 2500 kJ/kg, given hf=417.36 kJ/kg and hfg=2257.9 kJ/kg, is approximately:

According to the First Law of Thermodynamics for a closed system: dU = δQ - δW. If a gas is compressed adiabatically, which is true?

A throttling process (Joule-Thomson expansion) through a valve is characterized by:

In a Otto cycle (spark ignition engine), which process is isochoric (constant volume)?

For a reversible process in an isolated system (adiabatic, no work), the entropy change is:

The van der Waals equation accounts for real gas behavior with correction terms. Which statement is correct?

A gas expands isothermally from 2 m³ to 4 m³ at 300 K. If the initial pressure is 200 kPa, what is the work done by the gas?

A Brayton cycle operates with pressure ratio of 8:1. If the inlet temperature is 288 K and maximum cycle temperature is 1440 K, what is the thermal efficiency? (Take γ = 1.4)

A refrigerator operates between -10°C and 40°C. If the compressor removes 100 kJ from the cold space, what is the minimum work required?

In a throttling process, which property remains constant?

The mean effective pressure (MEP) of a four-stroke engine is 8 bar. If the stroke length is 100 mm and bore diameter is 80 mm, what is the power output at 1500 RPM?

A heat pump operates with a coefficient of performance (COP) of 4. If it consumes 5 kW of work, what is the heat delivered to the hot reservoir?

In an adiabatic process of an ideal gas with γ = 1.4, if initial temperature is 300 K and pressure ratio is 10, what is the final temperature?