mechanical engineering MCQs – Page 83

Practise multiple-choice questions from mechanical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

4101. In axial flow fans and turbines, fluid enters and leaves as follows________________?
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A. axially, axially

B. axially, radially

C. combination of axial and radial

D. radially, radially

E. radially, axially

4102. In reaction turbine, draft tube is used_____________________?
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A. none of the above

B. to transport water downstream without eddies

C. to increase flow rate

D. for safety of turbine

E. to convert the kinetic energy to flow energy by a gradual expansion of the flow cross-section
4103. Reciprocating pumps are no more to be seen in industrial applications (in comparison to centrifugal pumps) because of____________________?
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A. necessity of air vessel

B. all of the above

C. lower discharge

D. lower speed of operation

E. high initial and maintenance cost
4104. In a centrifugal pump casing, the flow of water leaving the impeller, is___________________?
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A. forced vortex

B. free vortex motion

C. none of the above

D. rectilinear flow

E. radial flow

4105. In centrifugal pumps, maximum efficiency is obtained when the blades are_________________?
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A. straight

B. bent forward

C. radial

D. given aerofoil section

E. bent backward
4106. High specific speed of turbine implies it is__________________?
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A. any one of the above

B. impulse turbine

C. Francis turbine

D. propeller turbine

E. none of the above

4107. Axial flow pump is started with its delivery valve________________?
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A. none of the above

B. kept 50% open

C. irrespective of any position

D. kept fully open

E. kept fully closed

4108. Pressure intensifier increases the pressure in proportion to____________________?
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A. fourth power of ratio of diameters

B. ratio of diameters

C. inverse ratio of diameters

D. square of inverse ratio of diameters

E. square of ratio of diameters
4109. For small discharge at high pressure, following pump is preferred_____________________?
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A. reciprocating

B. mixed flow

C. centrifugal

D. propeller

E. axial flow

4110. When a piping system is made up primarily of friction head and very little of vertical lift, then pump characteristics should be__________________?
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A. steep

B. first rise and then fall

C. none of the above

D. nearly horizontal

E. horizontal

4111. High specific speed of a pump implies it is_____________________?
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A. centrifugal pump

B. any one of the above

C. axial flow pump

D. mixed flow pump

E. none of the above

4112. Multistage centrifugal pumps are used to obtain___________________?
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A. pumping of viscous fluids

B. high head

C. high discharge

D. high head and high discharge

E. high efficiency

4113. Indicator diagram of a reciprocating pump is a graph between________________?
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A. flow vs swept volume

B. pressure in cylinder vs swept volume

C. swept volume vs speed

D. flow vs speed

E. pressure vs speed

4114. When a piping system is made up primarily of vertical lift and very little pipe friction, the pump characteristics should be _________________?
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A. horizontal

B. first rise and then fall

C. steep

D. nearly horizontal

E. none of the above

4115. Puck up the wrong statement about centrifugal pump_______________?
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A. Power a speed3

B. none of the above is wrong

C. head a speed2

D. discharge a diameter

E. head a diameter

4116. According to fan laws, at constant weight of air or gas, the speed, capacity and pressure vary________________?
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A. as square root of density

B. as square of density

C. directly as the air or gas density

D. inversely as square root of density

E. inversely as density
4117. Which place in hydraulic turbine is most susceptible for cavitation __________________?
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A. draft tube exit

B. penstock

C. inlet of draft rube

D. blade inlet

E. guide blade

4118. According to fan laws, for the fans having constant wheel diameters, the power demand varies_______________?
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A. square root of fan speed

B. directly as fan speed

C. none of the above

D. cube of fan speed

E. square of fan speed

4119. Maximum impulse will be developed in hydraulic ram when ___________________?
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A. waste valve closes suddenly

B. supply pipe is long

C. supply pipe has critical diameter

D. ram chamber is large

E. supply pipe is short

4120. Centrifugal pump is started with its delivery valve __________________?
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A. kept fully closed

B. kept 50% open

C. kept fully open

D. irrespective of any position

E. none of the above

4121. Head developed by a centrifugal pump depends on___________________?
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A. A. and B. above

B. fluid density

C. impeller diameter

D. speed

E. type of casing

4122. Specific speed for reaction turbines ranges from___________________?
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A. 250 to 300

B. 10 to 100

C. none of the above

D. 80 to 200

E. 0 to 4.5

4123. In a centrifugal pump casing, the flow of water leaving the_______________?
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A. centrifugal

B. radial

C. rectilinear

D. vortex

E. radial

4124. A hydraulic accumulator normally consists of________________?
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A. special type of pump with storage device and a pressure regulator

B. two cylinders, two rams and a storage device

C. a cylinder, a piston, storage tank and control valve

D. a cylinder and a ram

E. two co-axial rams and two cylinders

4125. The optimum value of vane exit angle for a centrifugal pump impeller is_________________?
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A. 10-15

B. 30-40

C. 50-60

D. 20-25

E. 80-90.

4126. According to fan laws, at constant pressure, the speed capacity and power vary_________________?
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A. as square of density

B. as square root of density

C. inversely as density

D. inversely as square root of density

E. directly as the air or gas density

4127. Casting of a centrifugal pump is designed so as to minimize________________?
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A. loss of kinetic energy

B. cavitation

C. friction loss

D. starting time

E. static head

4128. Impulse turbine is generally fitted______________________?
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A. about 2.5 m above the tail race to avoid cavitation

B. about 2.5 m below the tail race to avoid cavitation

C. at the level of tail race

D. slightly below the tail race

E. little above the tail race
4129. According to fan laws, at constant speed and capacity, the pressure and power vary_____________________?
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A. as square of density

B. inversely as density

C. as square root of density

D. directly as the air or gas density

E. inversely as square root of density

4130. According to fan laws, for fans having constant wheel diameter, the air or gas capacity varies______________________?
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A. directly as fan speed

B. cube of fan speed

C. square of fan speed

D. none of the above

E. square root of fan speed

4131. The discharge through a reaction turbine with increase in unit speed____________________?
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A. first increases and then decreases

B. remains unaffected

C. increases

D. first decreases and then increases

E. decreases
4132. The hydraulic turbines are also known as : ___________?
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A. steam turbines

B. combustion turbines

C. water turbines

D. Gas turbines

4133. For very high discharge at low pressure such as for flood control and irrigation applications, following type of pump is preferred_________________?
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A. reciprocating

B. none of the above

C. centrifugal

D. mixed flow

E. axial flow
4134. Guide angle as per the aerofoil theory of Kaplan turbine blade design is defined as the angle between_________________?
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A. lift and tangential force

B. drag and resultant force

C. lift and resultant force

D. resultant force and tangential force

E. lift and drag

4135. Francis turbine is best suited for_____________________?
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A. medium head application from 24 to 180 m

B. all types of heads

C. low head installation up to 30 m

D. none of the above

E. high head installation above 180 m

4136. A turbine pump is basically a centrifugal pump equipped additionally with_________________?
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A. totally submerged operation facility

B. inlet guide blades

C. vaned diffusion casing

D. adjustable blades

E. backward curved blades

4137. Low specific speed of turbine implies it is__________________?
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A. propeller turbine

B. none of the above

C. any one of the above

D. Francis turbine

E. impulse turbine
4138. The maximum number of jets generally employed in impulse turbine without jet interference is________________?
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A. 16

B. 4

C. 6

D. 8

E. 12

4139. If a pump is handling water and is discharging a certain flow Q at a constant total dynamic head requiring a definite B.H.P., the same pump when handling a liquid of specific gravity 0.75 and viscosity nearly same as of water would discharge_____________________?
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A. same quantity of liquid

B. none of the above

C. 1.5 Q

D. 0.75 Q

E. Q/0.75

4140. Medium specific speea of turbine implies it is___________________?
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A. none of the above

B. propeller turbine

C. Francis turbine

D. any one of the above

E. impulse turbine

4141. Any change in load is adjusted by adjusting following parameter on turbine______________?
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A. net head

B. relative velocity of flow at inlet

C. absolute velocity

D. flow

E. blade velocity

4142. Saving of work done and power by fitting an air vessel to double acting reciprocating pump is of the order of_______________?
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A. 39.2%

B. 68.80%

C. 91.6%.

D. 84.80%

E. 49.20%

4143. Air vessels in reciprocating pump are used to__________________?
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A. reduce acceleration to minimum

B. save pump from cavitation

C. increase pump efficiency

D. smoothen flow

E. increase pump head

4144. Motion of a liquid in a volute casing of a centrifugal pump is an example of____________________?
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A. spiral vortex flow

B. forced cylindrical vortex flow

C. rotational flow

D. radial

E. forced spiral vortex flow

4145. The efficiency of a centrifugal pump is maximum when its blades are__________________?
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A. bent backward first and then forward

B. bent backward

C. bent forward

D. straight

E. bent forward first and then backward

4146. One horsepower is equal to_________________?
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A. 33000 watts

B. 736 watts

C. 102 watts

D. 550 watts

E. 75 watts

4147. A hydraulic intensifier normally consists of __________________?
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A. special type of pump with storage device and a pressure regulator

B. a cylinder and a ram

C. two co-axial rams and two cylinders

D. a cylinder, a piston, storage tank and control valve

E. two cylinders, two rams and a storage device

4148. Low specific speed of a pump implies it is____________________?
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A. centrifugal pump

B. none of the above

C. any one of the above

D. mixed flow pump

E. axial flow pump

4149. Reaction turbines are used for____________________?
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A. high head

B. low head and high discharge

C. low head

D. high head and high discharge

E. high head and low discharge

4150. The angle of taper on draft tube is A. greater than 15 B. greater than 8 C. greater than 5 D. less than 8 E. less than 3.___________________?
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A. greater than 5

B. less than 3.

C. angle of taper on draft tube is

D. less than 8

E. greater than 8

F. greater than 15