Mechanical Engineering - MCQ Practice Questions

In a Diesel cycle, which process represents constant pressure heat addition?

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?

In a constant volume process (isochoric), if temperature increases from 300 K to 600 K, the pressure ratio P₂/P₁ will be:

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)

Which law states that the total energy of an isolated system remains constant?

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?

Which process is represented when a gas is compressed without any heat transfer to or from surroundings?

For an ideal gas, if both pressure and volume are doubled, the temperature ratio T₂/T₁ will be:

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?

Entropy change for a reversible isothermal process where heat Q is absorbed is:

In a closed system, 50 kJ of heat is added and 30 kJ of work is done by the system. The change in internal energy is:

The dryness fraction of a wet steam sample is 0.8. If specific enthalpy of saturated liquid and vapor at a pressure are 500 kJ/kg and 2700 kJ/kg respectively, the specific enthalpy of the mixture is:

Which of the following processes follows the path PV^n = constant?

A steam turbine receives steam at 5 MPa, 400°C with an enthalpy of 3231 kJ/kg. It exits at 0.1 MPa with enthalpy 2675 kJ/kg. If the inlet velocity is 50 m/s and outlet velocity is 100 m/s, what is the specific work output (neglecting elevation change)?

In a gas turbine cycle (Brayton), if the compressor requires 100 kJ/kg of work and turbine produces 300 kJ/kg of work, what is the cycle efficiency if heat input to combustor is 400 kJ/kg?

According to the Second Law of Thermodynamics, for a spontaneous process in an isolated system, the entropy must:

A rigid tank contains 2 kg of nitrogen gas at 100 kPa and 25°C. Heat is added until the pressure reaches 500 kPa. Assuming constant specific heats (Cv = 0.745 kJ/kg·K for N₂), what is the final temperature of the gas?