This set of Mechanical Operations Assessment Questions and Answers focuses on “Filtration in a Centrifuge”.
1. If the settling is carried out with high concentrations of solids to liquid so that particles close together, the condition is called as _______
a) Hindered settling
b) Terminal settling
c) Gross settling
d) Fundamental settling
View Answer
Explanation: When particle are close together that collision between the particles is continuous and relative fall of particles occur, it is called as hindered settling.
2. The selection of material handling system depends upon the constituents particles.
a) True
b) False
View Answer
Explanation: The selection of particles for a certain product depends upon the nature of characteristics of the material.
3. ______ is the percentage of total volume not occupied by the particles.
a) Free space
b) Void age
c) Open volume
d) Gross volume
View Answer
Explanation: A bulk solid is a combination of particles and space and the percentage of total volume not occupied by the particles is referred as void age.
4. What does the below equation represent?
a) Void density
b) Bulk density
c) Weight fraction
d) Mole fraction
View Answer
Explanation: The apparent or bulk density of granular material is defined as the mass of the material divided by its total volume of particles and voids.
5. ______ is defined as the mass of the solids divided by volume occupied by the solids.
a) True density
b) Bulk density
c) Void density
d) Mole fraction
View Answer
Explanation: True density is defined as the mass of the solids divided by volume occupied by the solid i.e (Mass of solid/Volume) and its unit is Kg/m3.
6. What does the following represents?
ρb=ρa(1- ϵ)
a) Relation of particle a and b
b) Relation of bulk and true densities
c) Relation of two void age
d) Can’t be specified
View Answer
Explanation: The relation between the apparent and true densities is given by the following relation, where ε is the void age of the particles.
7. Bulk density of a mixture depends upon ______
a) Weight of particles
b) Density of particles
c) Size of particles
d) Shape of particles
View Answer
Explanation: Bulk density of a mixture of particles different sizes will depend upon the extent to which particles are able to fit into the space among them.
8. What are the sizes of a coarse solid?
a) 5 – 100 mm
b) 0.3 – 5 mm
c) 10 -100 micrometer
d) < 1 micrometer
View Answer
Explanation: The coarse solid are in the range of particle size between 5 to 100 millimeter, whereas fine particles are of range in micrometer, common examples are coal.
9. What are the sizes of a coarse powder?
a) 5 – 100 mm
b) 0.3 – 5 mm
c) 100 – 300 micrometer
d) 5 to 100 micrometer
View Answer
Explanation: The best example of a coarse powder is the table salt and the wheat flour that we use, particles at range of 0.3 to 5 mm are granular in nature.
10. If the angle of repose is said to be 260, then it is ____
a) Very free flowing
b) Free flowing
c) Cohesive
d) Very cohesive
View Answer
Explanation: When a quantity of solid is allowed to form a heap, the surface angle is angle of repose, if at 260 then has a very free flowing type of nature while free flowing in 350.
Sanfoundry Global Education & Learning Series – Mechanical Operations.
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