Hydraulics & Fluid Machineries MCQ Solved Paper for LSAT

1. 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

2. The discharge through a reaction turbine with increase in unit speed
A. Increases
B. Decreases
C. Remain unaffected
D. First increases and then decreases
Answer : B

3. 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

4. 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

5. High 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 : C

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

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

13. In a single casing, multistage pump running at constant speed, the capacity rating is to be slightly lowered. It can be done by
A. Designing new impeller
B. Trimming the impeller size to the required size by machining
C. Not possible
D. Some other alterations in the impeller
Answer : B

14. For small discharge at high pressure, following pump is preferred
A. Centrifugal
B. Axial flow
C. Mixed flow
D. Reciprocating
Answer : D

15. 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

16. 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

17. 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

18. 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

19. 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

20. For starting an axial flow pump, its delivery valve should be
A. Closed
B. Open
C. Depends on starting condition and flow desired
D. Could be either open or closed
Answer : B

21. The efficiency of jet propulsion for a ship with inlet orifices at right angles to the direction of motion of ship is given by
A. [2(V_r - v) v]/ V_r²
B. 2(V_r + v) v]/ V_r²
C. [(V_r - v) v]/ V_r
D. [(V_r + v) v]/ V_r
Answer : A

22. In an inward 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 : C

23. The efficiency of a Pelton wheel working under constant head ________ with the increase in power.
A. Remain same
B. Increases
C. Decreases
D. None of these
Answer : B

24. 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

25. 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

26. The speed of a turbine runner is
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 : A

27. 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

28. 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

29. In impulse Turbine, energy available at the inlet is in the form of
A. Potential Energy
B. Strain Energy
C. Kinetic energy
D. None of these
Answer : C

30. 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

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

32. 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

33. 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

34. 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, the horse power required will be
A. Same
B. 0.75 B.H.P.
C. B.H.P./0.75
D. 1.5 B.H.P.
Answer : B

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

36. Which of the following pump is successfully used for lifting water to the boilers?
A. Centrifugal pump
B. Reciprocating pump
C. Jet pump
D. Airlift pump
Answer : C

37. 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

38. 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

39. 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

40. 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

41. For very high discharge at low pressure such as for flood control and irrigation applications, following type of pump is preferred
A. Centrifugal
B. Axial flow
C. Reciprocating
D. Mixed flow
Answer : B

42. 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

43. 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

44. 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

45. 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

46. The static head of a centrifugal pump is equal to the ________ of suction head and delivery head.
A. Product
B. Difference
C. Sum
D. None of these
Answer : C

47. 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

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

49. 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

50. 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