Hydraulics & Fluid Machineries 1000+ MCQ with answer for UPSC CDS

1. Casting of a centrifugal pump is designed so as to minimize
A. Friction loss
B. Cavitations
C. Static head
D. Loss of kinetic energy
Answer : D

2. 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

3. 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

4. According to fan laws, at constant speed and capacity, the pressure and power vary
A. Directly as the air or gas density
B. Inversely as square root of density
C. Inversely as density
D. As square of density
Answer : A

5. Discharge (Q) of a centrifugal pump is given by (where D = Diameter of impeller at inlet, b = Width of impeller at inlet, and Vf = Velocity of flow at inlet)
A. Q = ?.D.Vf
B. Q = ?.b.Vf
C. Q = ?.D.bf.V
D. Q = D.b.Vf
Answer : C

6. According to fan laws, for the fans having constant wheel diameters, the power demand varies
A. Directly as fan speed
B. Square of fan speed
C. Cube of fan speed
D. Square root of fan speed
Answer : C

7. The unit power developed by a turbine is (where P = Power developed by the turbine under a head of water (H).
A. P/ ?H
B. P/ H
C. P/ H^3/2
D. P/ H²
Answer : C

8. 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

9. Discharge of a centrifugal pump is
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

10. The maximum hydraulic efficiency of an impulse turbine is (where ? = Angle of blade tip at outlet)
A. (1 + cos ?)/2
B. (1 - cos ?)/2
C. (1 + sin ?)/2
D. (1 - sin ?)/2
Answer : A

11. 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

12. Power required (in watts) to drive a centrifugal pump is (where H_m = Manometric head in metres, w = Specific weight in N/m³, Q = Discharge of the pump in m³/s, and ?_o = Overall efficiency of the pump)
A. (w H_m) / (Q × ?_o)
B. (w H_m Q) / ?_o
C. (w Q) / (H_m × ?_o)
D. (w Q ?_o) / H_m
Answer : B

13. 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

14. 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

15. In centrifugal pumps, maximum efficiency is obtained when the blades are
A. Straight
B. Bent forward
C. Bent backward
D. Radial
Answer : C

16. A hydraulic accumulator normally consists of
A. Two cylinders, two rams and a storage device
B. A cylinder and a ram
C. Two coaxial rams and two cylinders
D. A cylinder, a piston, storage tank and control valve
Answer : B

17. A hydraulic intensifier normally consists of
A. Two cylinders, two rams and a storage device
B. A cylinder and a ram
C. Two coaxial rams and two cylinders
D. A cylinder, a piston, storage tank and control valve
Answer : C

18. Pressure intensifier increases the pressure in proportion to
A. Ratio of diameters
B. Square of ratio of diameters
C. Inverse ratio of diameters
D. Square of inverse ratio of diameters
Answer : B

19. 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

20. For 450 m head of water, _________ shall be used.
A. Pelton wheel
B. Kaplan turbine
C. Francis turbine
D. None of these
Answer : A

21. 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

22. If the ratios 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

23. 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

24. 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

25. A turbine is required to develop 1500 kW at 300 r.p.m. under a head of 150 m. Which of the following turbine should be used?
A. Pelton wheel with one nozzle
B. Pelton wheel with two or more nozzles
C. Kaplan turbine
D. Francis turbine
Answer : A

26. Any change in load is adjusted by adjusting following parameter on turbine
A. Net head
B. Absolute velocity
C. Blade velocity
D. Flow
Answer : D

27. The specific speed (Ns) of a centrifugal pump is given by
A. (N?Q)/H^2/3
B. (N?Q)/H^3/4
C. (N?Q)/H
D. (N?Q)/H^5/4
Answer : B

28. Saving of work done and power by fitting an air vessel to single acting reciprocating pump is of the order of
A. 39.2 %
B. 49.2 %
C. 68.8 %
D. 84.8 %
Answer : D

29. In a centrifugal pump casing, the flow of water leaving the impeller, is
A. Rectilinear flow
B. Radial flow
C. Free vortex motion
D. Forced vortex
Answer : C

30. 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 speed of the wheel is
A. 10 r.p.m.
B. 20 r.p.m.
C. 40 r.p.m.
D. 80 r.p.m.
Answer : B

31. The force exerted (in Newton) by a jet of water impinging normally on a fixed plate is (where w = Specific weight of water in N/m3, a = Crosssectional area of jet in m², and V = Velocity of jet in m/s)
A. waV / 2g
B. waV / g
C. waV² / 2g
D. waV² / g
Answer : D

32. 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

33. 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

34. 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

35. Saving of work done and power by fitting an air vessel to double acting reciprocating pump is of the order of
A. 39.2 %
B. 49.2 %
C. 68.8 %
D. 84.8 %
Answer : A

36. 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

37. 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

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 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

40. Guide angle as per the aerofoil theory of Kaplan turbine blade design is defined as the angle between
A. Lift and resultant force
B. Drag and resultant force
C. Lift and tangential force
D. Lift and drag
Answer : A

41. The flow rate in gear pump
A. Increases with increase in pressure
B. Decreases with increase in pressure
C. More or less remains constant with increase in pressure
D. Unpredictable
Answer : C

42. Puck up the wrong statement about centrifugal pump
A. Discharge a diameter
B. Head a speed²
C. Head a diameter
D. Power a speed?
Answer : A

43. 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

44. 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

45. 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

46. 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

47. 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

48. 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

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

50. Maximum impulse will be developed in hydraulic ram when
A. Waste valve closes suddenly
B. Supply pipe is long
C. Supply pipe is short
D. Ram chamber is large
Answer : A