Engineering Questions with Answers - Multiple Choice Questions
Environmental Engineering MCQ’s – Hydraulic Elements of Circular Sewers
1 - Question
Which of the following is incorrect regarding circular sewer?
a) It is easily manufactured
b) It offers more opportunities for deposits
c) It is the most economical section
d) It has uniform curvature
View Answer
Answer: b
Explanation: The circular section has uniform curvature, so it offers less opportunities for deposits.
2 - Question
A circular section of sewer gives _______ area for a given perimeter.
a) Small
b) Large
c) Minimum
d) Maximum
View Answer
Answer: d
Explanation: A circular section of sewer gives a maximum area for a given perimeter and gives the greatest hydraulic mean depth when running full or half.
3 - Question
What is the wetted perimeter of a circular section of sewer?
a) (22/7) *D2
b) (22/7) *D
c) (22/7) *D2
d) (22/7)2 *D
View Answer
Answer: b
Explanation: The wetted perimeter of a circular section of sewer running full is (22/7) *D where D is the internal diameter of circular sewer.
4 - Question
The hydraulic mean depth of a circular section running full is __________
a)`D
b) D/2
c) D2
d) D/4
View Answer
Answer: d
Explanation: The hydraulic mean depth, R = Area of cross section / Wetted perimeter
= ((22/7) *D2/4) / (22/7) *D
= D/4.
5 - Question
The proportional depth of a circular sewer running partially half is __________
a) (1-cosK/2)
b) (1/2) * (1-sinK/2)
c) (1/2) * (1-cosK/2)
d) (1-cosK/2)2
View Answer
Answer: c
Explanation: Depth of flow d = (D/2) * (1-cosK/2)
Proportional depth = Depth of flow d / Diameter of section D = (D/2) * (1-cosK/2) / D
= (1/2) * (1-cosK/2).
6 - Question
The proportional perimeter of a circular sewer running partially half where K is the central angle subtended at a circular section of sewer is __________
a) K/360o
b) K/90o
c) K/270o
d) K/180o
View Answer
Answer: a
Explanation: Proportional perimeter of a circular sewer running partially half =
(22/7) *D*K/360o / ((22/7) *D) = K/360o.
7 - Question
The diameter of the circular sewer is 0.2m. The desired depth of flow is __________
a) 2/3 of the circular section of sewer
b) 1/3 of the circular section of sewer
c) 1/2 of the circular section of sewer
d) 1/4 of the circular section of sewer
View Answer
Answer: c
Explanation: When the diameter of the sewer is up to 0.4m, they are designed to flow at 1/2 depth.
8 - Question
The diameter of a circular sewer is 0.8m. The desired depth of flow is __________
a) 2/3 of the circular section of sewer
b) 1/3 of the circular section of sewer
c) 1/2 of the circular section of sewer
d) 1/4 of the circular section of sewer
View Answer
Answer: a
Explanation: When the diameter of the sewer is between 0.4m and 0.8m, they are designed to flow at 2/3 depth.
9 - Question
A circular sewer having 0.4m diameter is flowing with velocity 2m/Sec. If the gradient of sewer is 1 in 90. Find the value of Chezy’s coefficient?
a) 10
b) 30
c) 60
d) 40
View Answer
Answer: d
Explanation: Hydraulic mean depth, R = D/4 = 0.4/4 = 0.1m
Slope of sewer S = 1/100, velocity V = 1m/Sec
According to Chezy’s formula, V = C (RS) 1/2 = C* (0.1/90) 1/2 = C/30
C = V*30 = 2*30 = 60.