⚙️ Mechanical Eng Solved MCQs with Answers

Practice 934 approved ⚙️ Mechanical Eng questions with verified answers from the 🛠️ Engineering Essentials subject for Pakistan exams.

934 solved MCQs

The efficiency of Diesel cycle approaches to Otto cycle efficiency whenAnswer: cut-off is zero The entropy __________ in an irreversible cyclic process.Answer: increases The atomic mass of oxygen isAnswer: 16 The ratio of specific heat at constant pressure (cᵖ) and specific heat at constant volume (cᵛ) isAnswer: greater than one Carbonisation of coal consists ofAnswer: none of the above The efficiency of Stirling cycle is __________ Carnot cycle.Answer: equal to According to Gay-Lussac law for a perfect gas, p/T = constant, if v is kept constant.Answer: True There is no change in internal energy in an isothermal process.Answer: Correct If the value of n = 0 in the equation pvⁿ = C, then the process is calledAnswer: constant pressure process The value of specific heat at constant pressure (cᵖ) is __________ that of at constant volume (cᵛ).Answer: more than When coal is strongly heated continuously for 42 to 48 hours in the absence of air in a closed vessel, the process is known as __________ of fuel.Answer: carbonisation Which of the following is correct?Answer: Absolute pressure = Gauge pressure + Atmospheric pressure The distillation carried out in such a way that the liquid with the lowest boiling point is first evaporated and recondensed, then the liquid with the next higher boiling point is then evaporated and recondensed, and so on until all the available liquid fuels are separately recovered in the sequence of their boiling points. Such a process is calledAnswer: fractional distillation Which of the following statement is incorrect?Answer: The solid fuels have higher calorific value than liquid fuels. Which of the following gas is mostly used in town for street and domestic lighting and heating?Answer: Coal gas The value of gas constant (R) in S. I. units isAnswer: 287 J/kgK In the first law of thermodynamics, the total energy of the system remains constant.Answer: True The efficiency of Diesel cycle increases withAnswer: decrease in cut-off Coal gas is obtained by mixing coal and gas at ambient conditions.Answer: No According to Avogadro's law, the density of any two gases is __________ their molecular masses, if the gases are at the same temperature and pressure.Answer: directly proportional to The kinetic energy of molecules of a gas becomes zero at absolute zero temperature.Answer: Agree One kg of carbon monoxide requires __________ kg of oxygen to produce 11/7 kg of carbon dioxide gas.Answer: 4/7 The absolute zero temperature is taken asAnswer: -273°C The specific heat of water isAnswer: 4.187 The constant pressure, constant volume and constant pvn processes are regarded as irreversible process.Answer: True Stirling and Ericsson cycles areAnswer: reversible cycles When cut-off ratio is __________ the efficiency of Diesel cycle approaches to Otto cycle efficiency.Answer: zero A series of operations, which takes place in a certain order and restore the initial conditions at the end, is known asAnswer: thermodynamic cycle An isothermal process is governed byAnswer: Boyle's law The sum of internal energy (U) and the product of pressure and volume (p.v) is known asAnswer: enthalpy