# Flow Measuring Devices MCQs with Answers

### MODULE 4: FLOW MEASURING DEVICES

1. The discharge over a right angled notch is (where H = Height of liquid above the apex of notch)

Answer: Option D

2. A weir is said to be broad crested weir, if the width of the crest of the weir is __________ half the height of water above the weir crest.
A. equal to.
B. less than
C. more than
Answer: Option C

3. Coefficient of resistance is the ratio of
A. actual velocity of jet at vena contracta to the theoretical velocity
B. area of jet at vena contracta to the area of orifice
C. loss of head in the orifice to the head of water available at the exit of the orifice
D. actual discharge through an orifice to the dieoretical discharge
Answer: Option C

4. In order to measure the flow with a venturimeter, it is installed in
A. horizontal line
B. inclined line with flow upwards
C. inclined line with flow downwards
D. any direction and in any location
Answer: Option D

5. The discharge through a large rectangular orifice is given by (where H1 = Height of the liquid above the top of the orifice, H2 = Height of the liquid above the bottom of the orifice, b = Breadth of the orifice, and Cd = Coefficient of discharge)

Answer: Option C

6. The discharge over a rectangular notch is (where b = Width of notch, and H = Height of liquid, above the sill of the notch)

Answer: Option C

7. In a venturimeter, the velocity of liquid at throat is __________ than at inlet.
A. higher
B. lower
Answer: Option A

8. The coefficient of discharge for an external mouthpiece is
A. 0.375
B. 0.5
C. 0.707
D. 0.855

Answer: Option D
For External mouthpiece Cd = 0.855.
For internal mouthpiece (Running free) = 0.5.
For internal mouthpiece ( Running Full) = 0.707.
For convergent-divergent mouthpiece = 1.

9. The discharge over a rectangular weir, considering the velocity of approach, is (where H1 = Total height of water above the weir = H + Ha H = Height of water, over the crest of the weir, and Ha = Height of water, due to velocity of approach)

Answer: Option B

10. The discharge over a triangular notch is
A. inversely proportional to H3/2
B. directly proportional to H3/2
C. inversely proportional to H5/2
D. directly proportional to H5/2
Answer: Option D

11. A weir is usually made of masonry or concrete.
A. Yes
B. No
Answer: Option A

12. If a pitot tube is placed with its nose upstream, downstream or sideways, the reading will be the same in every case.
A. True

B. False
Answer: Option B

13. The length of the divergent cone in a venturimeter is __________ that of the convergent cone.
A. equal to
B. double
C. three to four times
D. five to six times
Answer: Option C

14. If a pitot tube is placed with its nose upstream, downstream or sideways, the reading will be the same in every case.
A. True
B. False
Answer: Option B

15. A flow in which each liquid particle does not have a definite path and the paths of individual
particles also cross each other, is called turbulent flow.
A. Agree
B. Disagree
Answer: Option A

16. In a short cylindrical external mouthpiece, the vena contracta occurs at a distance __________ the diameter of the orifice from the outlet of orifice.
A. equal to
B. one-fourth
C. one-third
D. one-half
Answer: Option B

17. The rise, in water level, which occurs during the transformation of the unstable shooting flow to the stable streaming flow is called hydraulic jump.
A. Yes
B. No
Answer: Option A

18. The most economical section of a trapezoidal channel is one which has hydraulic mean depth equal to
A. 1/2 depth
B. 1/2 breadth
C. 1/2 sloping side
D. 1/4 (depth + breadth)
Answer: Option A

19. Re-entrant or Borda’s mouthpiece is an __________ mouthpiece.
A. internal
B. external
Answer: Option A

20. In an internal mouthpiece, the absolute pressure head at vena contracta is __________ the
atmospheric pressure head by an amount equal to height of the liquid above the vena contracta.
A. less than
B. more than
Answer: Option A

21. The difference between the notch and weir is that the notch is of bigger size and the weir is of a smaller size.
A. Agree
B. Disagree
Answer: Option B

22. The most economical section of a rectangular channel is one which has hydraulic mean depth or hydraulic radius equal to
A. half the depth
B. half the breadth
C. twice the depth
D. twice the breadth
Answer: Option A

23. The viscosity of a liquid __________ its rate of flow through a hole in a vessel.
A. effects
B. does not effect
Answer: Option A

24. The discharge through a channel of trapezoidal section is maximum when
A. width of channel at the top is equal to twice the width at the bottom
B. depth of channel is equal to the width at the bottom
C. the sloping side is equal to half the width at the top
D. the sloping side is equal to the width at the bottom
Answer: Option C

25. The pressure of the liquid flowing through the divergent portion of a venturimeter
A. remains constant
B. increases
C. decreases
D. depends upon mass of liquid
Answer: Option C

26. An internal mouthpiece is said to be running free if the length of the mouthpiece is __________ the diameter of the orifice.
A. less than twice

B. more than twice
C. less than three times
D. more than three times
Answer: Option C

27. If the value of coefficient of discharge increases, the discharge through the orifice decreases.
A. True
B. False
Answer: Option B