⚙️ 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

Parson's reaction turbine is a __________ reaction turbine.Answer: 50 percent The turbine blades areAnswer: curved The variation of steam pressure in the nozzle depends uponAnswer: all of these Steam turbines are used forAnswer: all of these Parson's turbine is aAnswer: simple reaction turbine The value of the reheat factor varies fromAnswer: 1.02 to 1.06 The steam enters the nozzle at aAnswer: high pressure and a low velocity During adiabatic saturation process on unsaturated air __________ remains constant.Answer: wet bulb temperature The difference of supersaturated temperature and saturation temperature at that pressure is calledAnswer: degree of undercooling The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number isAnswer: equal to one A perfect black body is one whichAnswer: absorbs heat radiations of all wave lengths falling on it A perfect black body is one whichAnswer: absorbs heat radiations of all wave lengths falling on it Degree of saturation or percentage humidity isAnswer: the ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure. The ratio of the useful heat drop to the isentropic heat drop is calledAnswer: nozzle efficiency The coefficient of performance of Heat Pump is always __________ one.Answer: greater than The efficiency of steam turbines may be improved byAnswer: any one of these During a refrigeration cycle, heat is rejected by the refrigerant in aAnswer: condenser A refrigeration systemAnswer: removes heat from a low temperature body and delivers it to a high temperature body The subcooling in a refrigeration cycleAnswer: increases C.O.P. In a reaction turbine, when steam flows through the fixed blades,Answer: pressure decreases while velocity increases During sensible cooling of air __________ decreases.Answer: dry bulb temperature The critical radius is the insulation radius at which the resistance to heat flow isAnswer: minimum In case of solids, the heat transfer takes place according to radiation.Answer: Incorrect A water cooled condenser operates at a __________ condensing temperature than an air-cooled condenser.Answer: lower The relative humidity decreases as air gets wet.Answer: True The temperature of ammonia after compression in a vapour compression system isAnswer: 70 to 110° C The ratio of the actual damping coefficient to the critical damping coefficient is called damping factor.Answer: Yes When a body moves with simple harmonic motion, the product of its periodic time and frequency is equal toAnswer: one In a vibrating system, if the actual damping coefficient is 40 N/m/s and critical damping coefficient is 420 N/m/s, then logarithmic decrement is equal toAnswer: 0.6 For high speed engines, the cam follower should move withAnswer: cycloidal motion