Hydraulics & Fluid Machineries MCQ Solved Paper for CAT

1. The cavitation in a hydraulic machine is mainly due to
A. Low velocity
B. High velocity
C. Low pressure
D. High pressure
Answer : C

2. 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

3. 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

4. According to fan laws, at constant pressure, the speed capacity 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 : B

5. When a piping system is made up primarily of friction head and very little of vertical lift, then pump characteristics should be
A. Horizontal
B. Nearly horizontal
C. Steep
D. First rise and then fall
Answer : B

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

7. 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

8. 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

9. The relation between hydraulic efficiency (?_h), mechanical efficiency (?_m) and overall efficiency (?_o) is
A. ?_h = ?_o × ?_m
B. ?_m = ?_m × ?_h
C. ?_o = ?_h × ?_m
D. None of these
Answer : C

10. 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

11. Medium specific speed of turbine implies it is
A. Propeller turbine
B. Francis turbine
C. Impulse turbine
D. Any one of the above
Answer : B

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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 : D

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. High specific speed of turbine implies it is
A. Propeller turbine
B. Francis turbine
C. Impulse turbine
D. None of the above
Answer : A

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

29. 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

30. 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

31. The unit speed of the turbine runner is
A. N/?H
B. N/H
C. N/H^3/2
D. N/H²
Answer : A

32. Which of the following hydraulic unit is used for transmitting increased or decreased torque to the driven shaft?
A. Hydraulic ram
B. Hydraulic intensifier
C. Hydraulic torque converter
D. Hydraulic accumulator
Answer : C

33. 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

34. 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

35. 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

36. 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

37. Air vessels in reciprocating pump are used to
A. Smoothen flow
B. Reduce acceleration to minimum
C. Increase pump efficiency
D. Save pump from cavitations
Answer : B

38. 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 : A

39. 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. Workdone on the wheel to the energy (or head of water) actually supplied to the turbine
D. None of the above
Answer : A

40. 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

41. 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

42. Runaway speed of a hydraulic turbine is
A. Full load speed
B. The speed at which turbine runner will be damaged
C. The speed if the turbine runner is allowed to revolve freely without load and with the wicket gates wide open
D. The speed corresponding to maximum overload permissible
Answer : C

43. According to fan laws, at constant weight of air or gas, the speed, capacity and pressure 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 : C

44. 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

45. 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

46. Which place in hydraulic turbine is most susceptible for cavitations?
A. Inlet of draft rube
B. Blade inlet
C. Guide blade
D. Penstock
Answer : A

47. A turbine pump is basically a centrifugal pump equipped additionally with
A. Adjustable blades
B. Backward curved blades
C. Vaned diffusion casing
D. Inlet guide blades
Answer : C

48. 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

49. The power produced by the reaction turbine is ________ to the head of water.
A. Directly proportional
B. Inversely proportional
C. 4th power
D. None of these
Answer : A

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