Hydraulics & Fluid Machineries 1000+ MCQ with answer for LIC AAO

1. By fitting an air vessel to the reciprocating pump, there is always a saving of work done and subsequently saving of power. This saving in case of a single acting reciprocating pump is
A. 39.2 %
B. 48.8 %
C. 84.8 %
D. 88.4 %
Answer : C

2. In reaction turbine, draft tube is used
A. To transport water downstream without eddies
B. To convert the kinetic energy to flow energy by a gradual expansion of the flow cross-section
C. For safety of turbine
D. To increase flow rate
Answer : B

3. The efficiency of a hydraulic press is given by (where W = Weight lifted by ram, P = Force applied on plunger, A = Area of ram, and a = Area of plunger)
A. (W/p) × (A/a)
B. (p/W) × (a/A)
C. (W/p) × (a/A)
D. (p/W) × (A/a)
Answer : C

4. Axial flow pump is started with its delivery valve
A. Kept fully closed
B. Kept fully open
C. Irrespective of any position
D. Kept 50% open
Answer : B

5. The discharge through a reaction turbine ________ with the increase in unit speed.
A. Decreases
B. Increases
C. Remain same
D. None of these
Answer : A

6. The specific speed of a turbine is given by the equation
A. N?P / H^3/2
B. N?P / H²
C. N?P / H^5/4
D. N?P / H³
Answer : C

7. Medium specific speed of a pump implies it is
A. Centrifugal pump
B. Mixed flow pump
C. Axial flow pump
D. Any one of the above
Answer : B

8. If the ratio's of the corresponding forces acting at corresponding points 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 : C

9. 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

10. The specific speed of turbine is defined as the speed of a unit
A. Of such a size that it delivers unit discharge at unit head
B. Of such a size that it delivers unit discharge at unit power
C. Of such a size that it requires unit power per unit head
D. Of such a size that it produces unit horse power with unit head
Answer : D

11. 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

12. Low specific speed of a pump implies it is
A. Centrifugal pump
B. Mixed flow pump
C. Axial flow pump
D. None of the above
Answer : A

13. 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 : A

14. A hydraulic ram is a device used to
A. Store the energy of water
B. Increase the pressure of water
C. To lift water from deep wells
D. To lift small quantity of water to a greater height when a large quantity of water is available at a smaller height
Answer : D

15. 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

16. The discharge of a double acting reciprocating pump is (where L = Length of stroke, A = Cross-sectional area of piston, and N = Speed of crank in r.p.m.)
A. L.A.N
B. 2 L.A.N
C. (L.A.N)/60
D. (2 L.A.N)/60
Answer : D

17. A jet of water is striking at the centre of a curved vane moving with a uniform velocity in the direction of jet. For the maximum efficiency, the vane velocity is ________ of the jet velocity
A. One-half
B. One-third
C. Two-third
D. Three-fourth
Answer : B

18. The power developed by a turbine is (where H = Head of water under which the turbine is working)
A. Directly proportional to H^1/2
B. Inversely proportional to H^1/2
C. Directly proportional to H^3/2
D. Inversely proportional to H^3/2
Answer : C

19. Impulse turbine is generally fitted
A. At the level of tail race
B. Little above the tail race
C. Slightly below the tail race
D. About 2.5 m above the tail race to avoid cavitations.
Answer : B

20. 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

21. In a centrifugal pump casing, the flow of water leaving the
A. Radial
B. Axial
C. Centrifugal
D. Vortex
Answer : D

22. 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

23. 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

24. A double overhung Pelton wheel has
A. Two jets
B. Two runners
C. Four jets
D. Four runners
Answer : B

25. 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

26. Which of the following turbine is preferred for a specific speed of 60 to 300 r.p.m.?
A. Pelton wheel
B. Francis turbine
C. Kaplan turbine
D. None of these
Answer : B

27. Hydraulic accumulator is used for
A. Accumulating oil
B. Supplying large quantities of oil for very short duration
C. Generally high pressures to operate hydraulic machines
D. Supplying energy when main supply fails
Answer : D

28. 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 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 : A

29. Head developed by a centrifugal pump depends on
A. Impeller diameter
B. Speed
C. Fluid density
D. Both (A) and (B) above
Answer : D

30. 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

31. 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 : D

32. By fitting an air vessel to the reciprocating pump, there is always a saving of work done and subsequently saving of power. 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

33. The force exerted by a jet of water (in a direction normal to flow) impinging on a fixed plate inclined at an angle ? with the jet is
A. waV/2g × sin?
B. waV/g × sin?
C. waV²/2g × sin2?
D. waV²/g × sin?
Answer : C

34. Multistage centrifugal pumps are used to obtain
A. High discharge
B. High head
C. Pumping of viscous fluids
D. High head and high discharge
Answer : B

35. The unit discharge through the turbine is
A. Q/?H
B. Q/H
C. Q/H^3/2
D. Q/H²
Answer : A

36. Which of the following is not a reaction turbine?
A. Fourneyron turbine
B. Journal turbine
C. Thomson's turbine
D. Pelton wheel
Answer : D

37. Reciprocating pumps are no more to be seen in industrial applications (in comparison to centrifugal pumps) because of
A. High initial and maintenance cost
B. Lower discharge
C. Lower speed of operation
D. Necessity of air vessel
Answer : A

38. Discharge of a centrifugal pump is (where N = Speed of the pump impeller)
A. Directly proportional to N
B. Inversely proportional to N
C. Directly proportional to N²
D. Inversely proportional to N²
Answer : A

39. The depth of the bucket for a Pelton wheel is generally ________ the diameter of jet.
A. Equal to
B. 1.2 times
C. 1.8 times
D. Double
Answer : B

40. 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

41. 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

42. 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

43. 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 : C

44. 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

45. Indicator diagram of a reciprocating pump is a graph between
A. Flow vs. swept volume
B. Pressure in cylinder vs. swept volume
C. Flow vs. speed
D. Pressure vs. speed
Answer : B

46. The maximum number of jets generally employed in impulse turbine without jet interference is
A. 4
B. 6
C. 8
D. 12
Answer : B

47. In a Francis turbine runner, the numbers of blades are generally between
A. 2 to 4
B. 4 to 8
C. 8 to 16
D. 16 to 24
Answer : D

48. The force exerted by a jet of water impinging normally on a plate which due to the impact of jet, moves in the direction of jet with a velocity v is
A. [wa (V - v)]/2g
B. [wa (V - v)]/g
C. [wa (V - v)²]/2g
D. [wa (V - v²)]/g
Answer : D

49. The Fourneyron turbine is _________ reaction turbine.
A. An axial flow
B. An inward flow
C. An outward flow
D. A mixed flow
Answer : C

50. 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