⚙️ 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

A centrifugal pump will start delivering liquid only when the pressure rise in the impeller is equal to theAnswer: manometric head When the speed of the pump increases, its net positive suction head (NPSH) requirement decreases.Answer: Disagree A Francis turbine is used when the available head of water isAnswer: 25 m to 250 m The specific speed from 160 to 500 r.p.m. of a centrifugal pump indicates that the pump isAnswer: high speed with axial flow at outlet A hydraulic coupling belongs to the category ofAnswer: energy transfer machines The principle of jet propulsion is used in driving the ships and aeroplanes.Answer: Correct In the casing of a centrifugal pump, the kinetic energy of the water is converted into pressure energy before the water leaves the casing.Answer: True The speed of an imaginary turbine, identical with the given turbine, which will develop a unit power under a unit head, is known asAnswer: specific speed For centrifugal pump impeller, the maximum value of the vane exit angle isAnswer: 20° to 25° In a reaction turbine, the pressure head of water, while flowing over the vanes, is converted into kinetic head before leaving the wheel.Answer: Disagree Manometric head, in case of a centrifugal pump, is equal toAnswer: All of the above In an impulse turbine, the jet of water impinges on the bucket with a low velocity and after flowing over the vanes, leaves with a high velocity.Answer: False The capacity of a hydraulic accumulator is generally specified as the maximum amount of energy stored.Answer: True The maximum efficiency of jet propulsion of a ship with inlet orifices at right angles to the direction of motion of ship, isAnswer: 50% The breast water wheels are those in which the wheel runs partly by the weight of water and partly by the impulse of water.Answer: True The ratio of quantity of liquid discharged per second from the pump to the quantity of liquid passing per second through the impeller is known asAnswer: volumetric efficiency All the commercial liquid fuels are derived from natural petroleum (or crude oil).Answer: True A cycle consisting of one constant pressure, one constant volume and two isentropic processes is known asAnswer: Diesel cycle The efficiency and work ratio of a simple gas turbine cycle areAnswer: very low The amount of heat required to raise the temperature of the unit mass of gas through one degree at constant volume, is calledAnswer: specific heat at constant volume There is a loss of heat in an irreversible process.Answer: True An adiabatic process is one in whichAnswer: All of the above Water gas is obtained by passing air and a large amount of steam over waste coal at about 650°C.Answer: Incorrect When the gas is heated at constant volume, the heat supplied increases the internal energy of the gas.Answer: True Which of the following is the lightest and most volatile liquid fuel?Answer: Gasoline The processes occuring in open system which permit the transfer of mass to and from the system, are known asAnswer: flow processes Which of the following has the minimum atomic mass?Answer: Carbon Workdone in a free expansion process isAnswer: zero The pressure exerted by an ideal gas is __________ of the kinetic energy of all the molecules contained in a unit volume of gas.Answer: two-third The compression ratio for petrol engines isAnswer: 5 to 8