Hydraulic Machines MCQ Questions and Answers in Civil Engineering

Question. The cavitation in reaction turbines is avoided, to a great extent by ?
a) installing the turbine below the tail race level
b) using stainless steel runner of the turbine
c) providing highly polished blades to the runner
d) all of the above

Answer : D

Question. The width of the bucket for a Pelton wheel is generally .......... the diameter of jet. ?
a) double
b) three times
c) four times
d) five times

Answer : D

Question. The number of buckets on the periphery of a Pelton wheel is given by ?
a) (D / 2d) + 5
b) (D / 2d) + 10
c) (D / 2d) + 15
d) (D / 2d) + 20

Answer : C

Question. In a reaction turbine, the draft tube is used ?
a) to run the turbine full
b) to prevent air to enter the turbine
c) to increase the head of water by an amount equal to the height of the runner outlet above the tail race
d) to transport water to downstream

Answer : C

Question. The flow ratio of Francis turbine is defined as the ratio of the ?
a) velocity of flow at inlet to the theoretical jet velocity
b) theoretical velocity of jet to the velocity of flow at inlet
c) velocity of runner at inlet to the velocity of flow at inlet
d) none of the above

Answer : C

Question. Which of the following statement is correct ?
a) The centrifugal pump is suitable for large discharge and smaller heads
b) The centrifugal pump requires less floor area and simple foundation as compared to reciprocating pump
c) The efficiency of centrifugal pump is less as compared to reciprocating pump
d) all of the above

Answer : D

Question. In an outward flow reaction turbine ?
a) the water flows parallel to the axis of the wheel
b) the water enters at the centre of the wheel and then flows towards the outer periphery of the wheel
c) the water enters the wheel at the outer periphery and then flows towards the centre of the wheel
d) the flow of water is partly radial and partly axial

Answer : B

Question. Multi-stage centrifugal pumps are used to ?
a) give high discharge
b) produce high heads
c) pump viscous fluids
d) all of these

Answer : B

Question. In order to avoid cavitation in centrifugal pumps ?
a) the suction pressure should be high
b) the delivery pressure should be high
c) the suction pressure should be low
d) the delivery pressure should be low

Answer : C

Question. The speed ratio in case of Francis turbine varies from ?
a) 0.15 to 0.3
b) 0.4 to 0.5
c) 0.6 to 0.9
d) 1 to 1.5

Answer : C

Question. For 450 m head of water.............. shall be used ?
a) Pelton wheel
b) Kaplan turbine
c) Francis turbine
d) none of these

Answer : A

Question. Slip of a reciprocating pump is negative, when ?
a) suction pipe is short and pump is running at low speeds
b) delivery pipe is long and pump is running at high speeds
c) suction pipe is short and delivery pipe is long and the pump is running at low speeds
d) suction pipe is long and delivery pipe is short and the pump is running at high speeds

Answer : D

Question. A centrifugal pump will start delivering liquid only when the pressure rise in the impeller is equal to the ?
a) kinetic head
b) velocity head
c) manometric head
d) static head

Answer : C

Question. A Pelton wheel develops 1750 kW under a head of 100 metres while running at 200 r.p.m. and discharging 2500 litres of water per second. The unit power of the wheel is ?
a) 0.25 kW
b) 0.75 kW
c) 1.75 kW
d) 3.75 kW

Answer : C

Question. Discharge of a centrifugal pump ?
a) directly proportional to diameter of its impeller
b) inversely proportional to diameter of its impeller
c) directly proportional to (diameter)2 of its impeller
d) inversely proportional to (diameter)2 of its impeller

Answer : D

Question. Overall efficiency of a centrifugal pump is the ratio of ?
a) energy available at the impeller to the energy supplied to the pump by the prime mover
b) actual workdone by the pump to the energy supplied to the pump by the prime mover
c) energy supplied to the pump to the energy available at the impeller
d) manometric head to the energy supplied by the impeller per kN of water

Answer : B

Question. The centrifugal pump preferred for a specific speed between 80 to 160 r.p.m. is
a) slow speed with radial flow at outlet
b) medium speed with radial flow at outlet
c) high speed with radial flow at outlet
d) high speed with mixed flow at outlet

Answer : D

Question. In the above question, the saving in case of a double acting reciprocating pump is ?
a) 39.2 %
b) 48.8 %
c) 84.8 %
d) 88.4 %

Answer : A

Question. The initial setting time of rapid hardening cement should not be less than ?
a) 30 min
b) 1 hour
c) 4 hours
d) 8 hours

Answer : A

Question. A Pelton wheel is ?
a) tangential flow impulse turbine
b) inward flow impulse turbine
c) outward flow impulse turbine
d) inward flow reaction turbine

Answer : A

Question. The hydraulic efficiency of an impulse turbine is maximum when velocity of wheel is ......... of the jet velocity ?
a) one-fourth
b) one-half
c) three-fourth
d) double

Answer : B

Question. The hydraulic efficiency of an impulse turbine is the ?
a) ratio of the actual power produced by the turbine to the energy actually supplied by the turbine
b) ratio of the actual work available at the turbine to the energy imparted to the wheel
c) ratio of the work done on the wheel to the energy of the jet
d) none of the above

Answer : C

Question. Mechanical efficiency of a centrifugal pump is the ratio of ?
a) energy available at the impeller to the energy supplied to the pump by the prime mover
b) actual work done by the pump to the energy supplied to the pump by the prime mover
c) energy supplied to the pump to the energy available at the impeller
d) manometric head to the energy supplied by the impeller per kN of water

Answer : A

Question. Which of the following is not a reaction turbine ?
a) Furneyron turbine
b) Jonval turbine
c) Thomson's turbine
d) Pelton wheel

Answer : D

Question. The maximum efficiency of jet propulsion of a ship with inlet orifices at right angles to the direction of motion of ship, is ?
a) 40 %
b) 50 %
c) 60 %
d) 80 %

Answer : B

Question. The hydraulic efficiency of a reaction turbine, is the ratio of ?
a) power produced by the turbine to the energy actually supplied by the turbine
b) actual work available at the turbine to energy imparted to the wheel
c) work done on the wheel to the energy (or head of water) actually supplied to the turbine
d) none of the above

Answer : C

Question. Which of the following statement is correct as regard to water wheels ?
a) They have slow speeds
b) They are suitable even for low water heads
c) They give constant efficiency, even if the discharge is not constant
d) all of the above

Answer : D

Question. Discharge of a centrifugal pump is ?
a) directly proportional to N
b) inversely proportional to N
c) directly proportional to N²
d) inversely proportional to N²

Answer : A

Question. If the ratio of all the corresponding linear dimensions are equal, then the model and the prototype are said to have ?
a) geometric similarity
b) kinematic similarity
c) dynamic similarity
d) none of these

Answer : A

Question. A hydraulic coupling belongs to the category of ?
a) power absorbing machines
b) power developing machines
c) energy transfer machines
d) energy generating machines

Answer : C

Question. The function of guide vanes in a reaction turbine is to ?
a) allow the water to enter the runner without shock
b) allow the water to flow over them, without forming eddies
c) allow the required quantity of water to enter the turbine
d) all of the above

Answer : D

Question. An impulse turbine is used for ?
a) low head of water
b) high head of water
c) medium head of water
d) high discharge

Answer : B

Question. Geometric similarity is said to exist between the model and the prototype, if both of them ?
a) have identical velocities
b) are equal in size and shape
c) are identical in shape, but differ only in size
d) have identical forces

Answer : C

Question. The cavitation in a hydraulic machine is mainly due to ?
a) low velocity
b) high velocity
c) low pressure
d) high pressure

Answer : C

Question. For centrifugal pump impeller, the maximum value of the vane exit angle is ?
a) 10° to 15°
b) 15° to 20°
c) 20° to 25°
d) 25° to 30°

Answer : C

Question. The undershot water wheels are those in which ?
a) the wheel runs entirely by the weight of water
b) the wheel runs entirely by the impulse of water
c) the wheel runs partly by the weight of water and partly by the impulse of water
d) none of the above

Answer : B

Question. Which of the following pump is suitable for small discharge and high heads ?
a) Centrifugal pump
b) Axial flow pump
c) Mixed flow pump
d) Reciprocating pump

Answer : D

Question. Which of the following turbine is preferred for 0 to 25 m head of water ?
a) Pelton wheel
b) Kaplan turbine
c) Francis turbine
d) none of these

Answer : B

Question. Which of the following statement is wrong ?
a) The reaction turbines are used for low head and high discharge
b) The angle of taper on draft tube is less than 8°
c) An impulse turbine is generally fitted slightly above the tail race
d) A Francis turbine is an impulse turbine

Answer : D

Question. If the ratios of the corresponding forces acting at corresponding points are equal, then model and the prototype are said to have ?
a) geometric similarity
b) kinematic similarity
c) dynamic similarity
d) none of these

Answer : C

Question. The cavitation in a hydraulic machine ?
a) causes noise and vibration of various parts
b) reduces the discharge of a turbine
c) causes sudden drop in power output and efficiency
d) all of the above

Answer : D

Question. The specific speed from 160 to 500 r.p.m. of a centrifugal pump indicates that the pump is ?
a) slow speed with radial flow at outlet
b) medium speed with radial flow at outlet
c) high speed with radial flow at outlet
d) high speed with axial flow at outlet

Answer : C

Question. The specific speed of a hydraulic turbine depends upon ?
a) speed and power developed
b) discharge and power developed
c) speed and head of water
d) speed, power developed and head of water

Answer : D

Question. Which of the following pump is successfully used for lifting water from deep wells? ?
a) Centrifugal pump
b) Reciprocating pump
c) Jet pump
d) Air lift pump

Answer : D

Question. If the net positive suction head (NPSH) requirement for the pump is not satisfied, then ?
a) no flow will take place
b) cavitation will be formed
c) efficiency will be low
d) excessive power will be consumed

Answer : B

Question. Delivery head of a centrifugal pump is ?
a) directly proportional to N
b) inversely proportional to N
c) directly proportional to N²
d) inversely proportional to N²

Answer : C

Question. Kinematic similarity is said to exist between the model and the prototype, if both of them ?
a) have identical velocities
b) are equal in size and shape
c) are identical in shape, but differ only in size
d) have identical forces

Answer : A

Question. Which of the following is not an impulse turbine ?
a) Girad turbine
b) Turgo turbine
c) Pelton wheel
d) Kaplan turbine

Answer : D

Question. Power required to drive a centrifugal pump is directly proportional to ......... of its impeller ?
a) diameter
b) square of diameter
c) cube of diameter
d) fourth power of diameter

Answer : D

Question. The jet ratio is defined as the ratio of the ?
a) diameter of jet to the diameter of Pelton wheel
b) velocity of jet to the velocity of Pelton wheel
c) diameter of Pelton wheel to the diameter of jet
d) velocity of Pelton wheel to the velocity of jet

Answer : C

Question. Slip of a reciprocating pump is defined as the ?
a) ratio of actual discharge to the theoretical discharge
b) sum of actual discharge and the theoretical discharge
c) difference of theoretical discharge and the actual discharge
d) product of theoretical discharge and the actual discharge

Answer : D

Question. The impeller of a centrifugal pump may have ?
a) volute casing
b) volute casing with guide blades
c) vortex casing
d) any one of these

Answer : D

Question. Which type of the pump is different from others in the same group ?
a) Screw pump
b) Gear pump
c) Cam and piston pump
d) Plunger pump

Answer : D

Question. The maximum number of jets, generally, employed in an impulse turbine without jet interference are ?
a) two
b) four
c) six
d) eight

Answer : C

Question. A Francis turbine is used when the available head of water is ?
a) 0 to 25 m
b) 25 m to 250 m
c) above 250 m
d) none of these

Answer : B

Question. Dynamic similarity is said to exist between the model and the prototype, if both of them ?
a) have identical velocities
b) are equal in size and shape
c) are identical in shape, but differ only in size
d) none of the above

Answer : D

Question. The speed of an imaginary turbine, identical with the given turbine, which will develop a unit power under a unit head, is known as ?
a) normal speed
b) unit speed
c) specific speed
d) none of these

Answer : C

Question. Which of the following pump is preferred for flood control and irrigation applications ?
a) Centrifugal pump
b) Axial flow pump
c) Mixed flow pump
d) Reciprocating pump

Answer : B

Question. Which of the following pump is generally used to pump highly viscous fluid ?
a) Centrifugal pump
b) Reciprocating pump
c) Air lift pump
d) Screw pump

Answer : D

Question. Braking jet in an impulse turbine is used ?
a) to break the jet of water
b) to bring the runner to rest in a short time
c) to change the direction of runner
d) none of these

Answer : B

Question. A double overhung Pelton wheel has ?
a) two jets
b) two runners
c) four jets
d) four runners

Answer : B

Question. In a Kaplan turbine runner, the number of blades are generally between ?
a) 2 to 4
b) 4 to 8
c) 8 to 16
d) 16 to 24

Answer : B

Question. In a reciprocating pump, air vessels are used to ?
a) smoothen the flow
b) reduce suction head
c) increase delivery head
d) reduce acceleration head

Answer : D

Question. The overall efficiency of a reaction turbine is the ratio of ?
a) power produced by the turbine to the energy actually supplied by the turbine
b) actual work available at the turbine to the energy imparted to the wheel
c) work done on the wheel to the energy (or head of water) actually supplied to the turbine
d) none of the above

Answer : A

Question. The flow ratio in case of Francis turbine varies from ?
a) 0.15 to 0.3
b) 0.4 to 0.5
c) 0.6 to 0.9
d) 1 to 1.5

Answer : A

Question. Which of the following pump is successfully used for lifting water to the turbines ?
a) Centrifugal pump
b) Reciprocating pump
c) Jet pump
d) Air lift pump

Answer : C

Question. The specific speed of a centrifugal pump, delivering 750 litres of water per second against a head of 15 metres at 725 r.p.m., is ?
a) 24.8 r.p.m
b) 48.2 r.p.m
c) 82.4 r.p.m
d) 248 r.p.m

Answer : C

Question. The working of which of the following hydraulic units is based on Pascal's law ?
a) Air lift pump
b) Jet pump
c) Hydraulic coupling
d) Hydraulic press

Answer : D

Question. Which of the following pump is successfully used for lifting water to the boilers ?
a) Centrifugal pump
b) Reciprocating pump
c) Jet pump
d) Air-lift pump

Answer : C

Question. Which of the following pump is preferred for flood control and irrigation applications ?
a) Centrifugal pump
b) Axial flow pump
c) Mixed flow pump
d) Reciprocating pump

Answer : B

Question. The runaway speed of a hydraulic turbine is the speed ?
a) at full load
b) at which there will be no damage to the runner
c) corresponding to maximum overload permissible
d) at which the turbine will run freely without load

Answer : B

Question. A Pelton wheel working under a constant head and discharge, has maximum efficiency when the speed ratio is ?
a) 0.26
b) 0.36
c) 0.46
d) 0.56

Answer : C

Question. The type of centrifugal pump preferred for a specific speed of 20 r.p.m. is ?
a) slow speed pump with radial flow at outlet
b) medium speed pump with radial flow at outlet
c) high speed pump with radial flow at outlet
d) high speed pump with axial flow at outlet

Answer : A

Question. The overall efficiency for a Pelton wheel lies between ?
a) 0.50 to 0.65
b) 0.65 to 0.75
c) 0.75 to 0.85
d) 0.85 to 0.90

Answer : D

Question. In a Francis turbine runner, the number of blades are generally between ?
a) 2 to 4
b) 4 to 8
c) 8 to 16
d) 16 to 24

Answer : D

Question. A hydraulic press is a device used ?
a) to store pressure energy which may be supplied to a machine later on
b) to increase the intensity of pressure of water by means of energy available from a large quantity of water at a low pressure
c) to lift larger load by the application of a comparatively much smaller force
d) all of the above

Answer : C

Question. The maximum hydraulic efficiency of an impulse turbine is ?
a) (1 + cos ?) / 2
b) (1 - cos ?) / 2
c) (1 + sin ?) / 2
d) (1 - sin ?) / 2

Answer : A

Question. Which of the following statement is correct ?
a) In an impulse turbine, the water impinges on the buckets with pressure energy
b) In a reaction turbine, the water glides over the moving vanes with kinetic energy
c) In an impulse turbine, the pressure of the flowing water remains unchanged and is equal to atmospheric pressure
d) In a reaction turbine, the pressure of the flowing water increases after gliding over the vanes

Answer : C

Question. The mechanical efficiency of an impulse turbine is ?
a) ratio of the actual power produced by the turbine to the energy actually supplied by the turbine
b) ratio of the actual work available at the turbine to the energy imparted to the wheel
c) ratio of the work done on the wheel to the energy of the jet
d) none of the above

Answer : B

Question. The specific speed of a turbine is the speed of an imaginary turbine, identical with the given turbine, which ?
a) delivers unit discharge under unit head
b) delivers unit discharge under unit speed
c) develops unit power under unit head
d) develops unit power under unit speed

Answer : C