Engineering Questions with Answers - Multiple Choice Questions
Mechanical Operations MCQ’s – Open and Closed Circuit Operation
1 - Question
When this interface approaches the layer of sediment, its rate of fall decreases until the _____
a) Final settling point
b) Critical settling point
c) Primer settling point
d) Kynch velocity
View Answer
Answer: b
Explanation: The critical settling point is reached when a direct interface is formed between the sediment and the clear liquid.
2 - Question
What does the following equation represents?
μc = μ(1 + k’’C)
a) Einstein formula
b) Newton’s formula
c) Kynch formula
d) Neymar formula
View Answer
Answer: a
Explanation: The above equation represents the Einstein formula for critical viscosity, where μ is the viscosity of fluid and k’’ is constant for a given shape.
Explanation: The above equation represents the Einstein formula for critical viscosity, where μ is the viscosity of fluid and k’’ is constant for a given shape.
3 - Question
The above below equation is used to calculate the _____
a) Rate of filtration
b) Rate of flotation
c) Rate of sedimentation
d) Rate of evaporation
View Answer
Answer: c
Explanation: The above equation approximately gives the rate of sedimentation, where H is the height of the sludge line at time t and b is constant for a given separation.
4 - Question
The plot of ln (H-H∞) against t, remits ___
a) A straight line
b) An elliptical curve
c) A hyperbolic curve
d) A parabolic curve
View Answer
Answer: a
Explanation: If ln (H − H∞) is plotted against t, a straight line of slope −b is obtained, the values of H∞ are determined largely by the surface film of liquid adhering to the particles.
5 - Question
The aggregation of colloids is known as ____
a) Coagulation
b) Fluctuation
c) Sedimentation
d) Precipitation
View Answer
Answer: a
Explanation: The aggregation of colloids is known as coagulation, or flocculation, particles dispersed in liquid media collide due to their relative motion.
6 - Question
Gravity thickening requires much higher torques than clarification.
a) True
b) False
View Answer
Answer: a
Explanation: Yes, it requires much higher torques than clarification, while clarifiers frequently require the inclusion of special flocculating devices.
7 - Question
At what distance the plates are kept?
a) 10 – 50 mm
b) 5 – 40 mm
c) 20 – 50 mm
d) 1 – 4 mm
View Answer
Answer: b
Explanation: Plates are placed at a distance of 5 to 40 mm, depending up on the conductivity of the liquid in use.
8 - Question
There will be no effect on rate of sedimentation, if ratio of diameter of vessel to particle is ___
a) <100
b) =100
c) >100
d) No effect
View Answer
Answer: c
Explanation: If ratio of diameter of vessel to particle is greater than 100, then there is no wall effect to the rate of sedimentation but can affect for smaller values.
9 - Question
The higher the concentration, the lower the ____
a) Density
b) Rate of escaping
c) Speed
d) Rate of fall
View Answer
Answer: d
Explanation: The higher the concentration, the lower will be the rate of fall of sludge line because the greater is upward velocity steeper the gradient.
10 - Question
The final consolidation is the ______ part.
a) Fastest
b) Slowest
c) Toughest
d) Extract
View Answer
Answer: b
Explanation: The final consolidation is the slowest part of the process because the displaced fluid has to flow through small spaces between particles.