⚙️ 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

One kg of carbon requires 4/3 kg of oxygen and produces __________ kg of carbon monoxide gas.Answer: 7/3 The behaviour of a perfect gas, undergoing any change in the variables which control physical properties, is governed byAnswer: all of these The universal gas constant of a gas is the product of molecular mass of the gas and the gas constant.Answer: Correct The object of producing draught in a boiler isAnswer: All of the above In a glass tube type water indicator for a boiler, one end of the tube is connected to water space and the other end is connected toAnswer: steam space In water tube boilersAnswer: water passes through the tubes which are surrounded by flames and hot gases Which of the following statement is wrong ?Answer: All of the above A grate, in a boiler, is a place in the combustion chamber upon which fuel (wood or coal) is burnt.Answer: True The wet bulb temperature during sensible heating of airAnswer: increases Loeffler boiler is a water tube boiler using a forced circulation of water.Answer: True In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of theAnswer: Prandtl number, Grashoff's number La-mont boiler, is a high pressure water tube steam boiler working on forced circulation.Answer: Agree The function of a connecting rod is not to convert reciprocating motion of the piston into rotary motion.Answer: False In a refrigerating machine, heat rejected is __________ heat absorbed.Answer: greater than Which of the following statement is correct for a compound steam engine ?Answer: The ratio of expansion is reduced, thus reducing the length of stroke. When the speed of the crankshaft is between 100 r.p.m. and 250 r.p.m., the engine said to be aAnswer: medium speed steam engine The humidity ratio or specific humidity is the mass of water vapour present inAnswer: 1 kg of dry air The formation of frost on cooling coils in a refrigeratorAnswer: increases power consumption The natural draught is produced byAnswer: chimney Willian's line for the steam engine is a straight line relationship between the steam consumption per hour andAnswer: indicated power The by-pass factor for a cooling coilAnswer: increases with increase in velocity of air passing through it The temperature of condensate is __________ on leaving the condenser than that of circulating water at inlet.Answer: higher The difference between dry bulb temperature and wet bulb temperature, is calledAnswer: wet bulb depression A draught produced by a chimney due to the difference of densities between the hot gases inside the chimney and cold atmospheric air outside it, is called natural draught.Answer: Yes Which of the following statement is correct ?Answer: A simple vertical boiler has one fire tube. Defrosting of a refrigerator may be done by stopping the compressor for a short period.Answer: Correct A device used to increase the temperature of saturated steam without raising its pressure, is calledAnswer: superheater According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)Answer: Pb = pa + pv The diameter of flue tube in a Cornish boiler is __________ that of the shell.Answer: three-fifth An economiser __________ the steam raising capacity of a boiler.Answer: increases