Orifice Meter MCQ | Orifice and Mouthpiece MCQ – Fluid Mechanics

1. The flow rate through a circular pipe is measured by

  1. pitot-tube
  2. venturimeter
  3. orifice meter
  4. none of the above


  1. i
  2. i, ii and iii
  3. ii and iii
  4. all of the above
Answer. c

2. The head loss is more in a

  1. venturimeter
  2. nozzle meter
  3. inclined venturimeter
  4. orifice meter
Answer. d

3. The loss of energy in orifice meter is more than in the case of venturimeter because of

  1. Sudden obstruction
  2. Turbulence
  3. pressure variation
  4. More friction
Answer. a

4. Orifices are used to measure

  1. rate of flow
  2. velocity
  3. pressure
  4. none of three mentioned here
Answer. a

5. In a standard orifice meter,

  1. the level edge is on the upstream
  2. the coefficient of discharge does not depend upon the location of taps
  3. the loss of head is less than that in a venturimeter
  4. the level angle is usually 30° to 45°
Answer. d

6. An orifice is called a large orifice if water head, is

  1. twice the diameter of the orifice
  2. thrice the diameter of the orifice
  3. four times the diameter of the orifice
  4. five times the diameter of the orifice
Answer. d

7. Two small orifices A and B of diameter 1 cm and 2 cm respectively, are placed on sides of a tank at depths of h1 and h2 below the open liquid surface. If discharges through A and B are equal, then ratio of h1 and h2 (assuming equal cd values) will be

  1. 16 : 1
  2. 8 : 1
  3. 4 : 1
  4. 2 : 1
Answer. b

8. In a short cylindrical external mouthpiece, the vena-contracta occurs at a distance from the outlet of orifice equal to

  1. Diameter of the orifice
  2. One-fourth the diameter of the orifice
  3. One-third the diameter of the orifice
  4. Two-third the diameter of the orifice
  5. Two times the diameter of the orifice
Answer. b

9. Coefficient of discharge in terms of orifice is, actual discharge ‘a’ and ideal discharge ‘d’ is

  1. a/d
  2. d/a
  3. (a + d)/d
  4. (a – d)/d
Answer. a

10. The coefficient of discharge for an external mouthpiece depends upon

  1. Velocity of liquid
  2. Pressure of liquid
  3. Area of mouthpiece
  4. Length of mouthpiece
Answer. d

11. Which mouthpiece has the maximum coefficient of discharge?

  1. External mouthpiece
  2. Convergent divergent mouthpiece
  3. Internal mouthpiece
  4. None of the above
Answer. b

12. A convergent mouth piece has the maximum value of coefficient of discharge (C) is about

  1. 0.60
  2. 0.95
  3. 0.50
  4. 0.80
Answer. b

13. The average value of coefficient of velocity is

  1. 0.76
  2. 0.84
  3. 0.62
  4. 0.97
Answer. d

14. Consider the following devices:

  1. Orifice
  2. Borda’s mouthpiece running free
  3. Bell-mouthed orifice
  4. External mouthpiece

What is the correct sequence of these devices in decreasing magnitude of coefficient of discharge?

  1. ii, iii, i, iv
  2. iv, iii, i, ii
  3. iv, i, iii, ii
  4. ii, i, iii, iv
Answer. b

15. Mouthpiece has increased net head when compared to small orifice due to

  1. turbulence in the tube
  2. vena contracta occurred within the tube
  3. smaller length of the tube
  4. smooth boundary of the tube
Answer. b

16. A mouthpiece and an orifice, both of the same diameter ‘d’, are discharging under the same head ‘H’. The discharge through the mouthpiece will be

  1. the same as that of the orifice
  2. less than that of the orifice
  3. more than that of the orifice
  4. no relationship
Answer. c

17. At vena contracta, the area of the water jet is minimum and the velocity of emerging water is

  1. minimum
  2. average
  3. maximum
  4. zero
Answer. c

18. An orifice discharges under a head of 1.25m of water. A pitot tube kept at its centre line at the vena contracta indicates a head of 1.20 m of water. The coefficient of velocity of the orifice is

  1. 0.980
  2. 0.990
  3. 0.965
  4. 0.9565
Answer. a

19. A vertical cylindrical tank, 2 m diameter has, at the bottom, a 5 cm diameter, sharp-edged orifice, for which Cd = 0.6. Water enters the tank at a constant rate of 9 l/sec. At what depth above the orifice will the level in the tank become steady?

  1. 2.95 m
  2. 2.75 m
  3. 2.60 m
  4. 2.50 m
Answer. a

20. The ratio of velocity of flow at exit to theoretical velocity of jet corresponding to manometric head is known as

  1. Specific speed
  2. Flow ratio
  3. Speed ratio
  4. Hydraulic ratio
Answer. b

21. The coefficient of discharge, Cd in terms of Cv and Cc is given (Notations have their usual meaning)

  1. Cv = Cd × Cc
  2. Cc = Cd × Cv
  3. Cd = Cc × Cv
  4. Cd = Cc – Cv
Answer. c

22. The height of water level in a tank above the centre of a circular hole 2.5 cm in diameter is 50m. The velocity of water flowing through the hole is (neglect friction between jet and wall)

  1. 25.85 m/sec
  2. 20.53 m/sec
  3. 40.40 m/sec
  4. 31.32 m/sec
Answer. d
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