⚙️ 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

Fire tube boilers areAnswer: internally fired A safety valve usually employed with stationary boilers isAnswer: all of these The draught produced by a steam jet issuing from a nozzle placed in the ashpit under the fire grate of the furnace is calledAnswer: forced steam jet draught The relative humidity is defined asAnswer: the ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure Which of the following statement is wrong ?Answer: None of the above The function of a crosshead is to guide motion of the __________ and to prevent it from bending.Answer: piston rod The heat transfer by conduction through a thick sphere is same as through a thick cylinder.Answer: False The cylinder dimensions of a compound engine may be designed on the basis ofAnswer: All of the above In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants are respectivelyAnswer: ammonia and water The function of a piston rod isAnswer: to transfer motion from the piston to the cross head An air preheater is installedAnswer: between the economiser and chimney The length of shell of a Locomotive boiler isAnswer: 4 m The effect of wire drawing is to decrease the area of indicator diagram and thus work done by the engine is reduced.Answer: Agree As relative humidity decreases, the dew point temperature will be __________ wet bulb temperature.Answer: lower than As relative humidity decreases, the dew point temperature will be __________ wet bulb temperature.Answer: lower than In a uniflow engineAnswer: steam enters at one end and exhausts at the centre The shell diameter of a Locomotive boiler isAnswer: 1.5 m The process of heat transfer from a hot body to a cold body, in a straight line, without affecting the intervening medium, is called radiation.Answer: True The fire tubes in a Scotch marine boiler areAnswer: horizontal The optimum effective temperature for human comfort isAnswer: lower in winter than in summer In a reciprocating steam engine, the heat energy in the steam is converted into mechanical work by the to and fro motion of the piston.Answer: Agree The power of a boiler may be defined asAnswer: the amount of water evaporated or steam produced in kg per kg of fuel burnt The wet bulb temperature lines, on the psychrometric chart, are curved lines.Answer: False When the circulation of water, in a boiler, is by a centrifugal pump, then the boiler is known asAnswer: forced circulation boiler Thermal diffusivity is aAnswer: physical property of a substance The function of a safety valve isAnswer: to blow off steam when the pressure of steam inside the boiler exceeds the working pressure The condition of refrigerant after leaving the compressor and before entering the condenser is superheated vapour.Answer: Yes The fire tubes in a Cochran boiler areAnswer: horizontal The total radiation from a black body per second per unit area is __________ fourth power of the absolute temperature. This statement is known as Stefan-Boltzmann law.Answer: directly proportional to A double acting steam engine with a cylinder diameter of 190 mm and a stroke of 300 mm has a cut-off of 0.35. The expansion ratio for this engine is nearlyAnswer: 2.86