Particle Technology

Question 1

Increasing the capacity of screen
a. decreases the screen effectiveness
b. does not affect the screen effectiveness c. increases the screen effectiveness
d. none of these

Answer 1

A

Question 2

Screen efficiency is

Answer 2

Recovery x Rejection

Question 3

As particle size is reduced
a. screening becomes progressively more difficult
b. screening becomes progressively easier
c. capacity and effectiveness of the screen is increased
d. none of these

Answer 3

A

Question 4

A screen is said to be blinded when
a. oversizes are present in undersize fraction
b. undersizes are retained in oversize fraction
c. the screen is plugged with solid particles
d. its capacity is abruptly increased

Answer 4

C

Question 5

The material passing one screening surface and retained on a subsequent surface is called

Answer 5

Intermediate Material

Question 6

In screen analysis, notation + 5 mm/ -10 mm means passing through
a. 10 mm screen and retained on 5 mm screen
b. 5 mm screen and retained on 10 mm screen
c. both 5 mm and 13 mm screens
d. neither 5 mm nor 10 mm screens

Answer 6

A

Question 7

Mesh number indicates the number of holes per

Answer 7

Linear Inch

Question 8

Size measurement of ultrafine particles can be best expressed in terms o

Answer 8

Surface area per unit mass

Question 9

The hardness of a mineral is a criterion of its resistance to crushing. Which of the following is an example of a hard material?

a. talc c. sapphire
b. calcite d. feldspar

Answer 9

C

Question 10

For the preliminary breaking of hard rock, we use

Answer 10

Gyratory crusher

Question 11

Size reduction mechanism used in jaw crushers is

Answer 11

Compression

Question 12

To get ultrafine particles, the equipment used is

Answer 12

Fluid energy mill

Question 13

Maximum size reduction in a ball mill is done by

Answer 13

Impact

Question 14

The operating speed of a ball mill should be
a. less than the critical speed
b. at least equal to the critical speed
c. much more than the critical speed
d. none of these

Answer 14

A

Question 15

As the product becomes finer, the energy required for grinding
a. decreases
b. is same as for coarser grinding
c. increases
d. is 1.5 times than for coarser grinding

Answer 15

C

Question 16

The operation by which solids are separated from liquids due to difference in the respective densities is

Answer 16

Sedimentation

Question 17

Forces acting on a particle settling in fluid are
a. gravitational and buoyant forces
b. centrifugal and drag forces
c. gravitational or centrifugal, buoyant and drag forces
d. external, drag and viscous forces

Answer 17

C

Question 18

Drag is defined as the force exerted by the
a. fluid on the solid in a direction opposite to flow
b. the fluid on the solid in the direction of flow
c. the solid on the fluid
d. none of these

Answer 18

A

Question 19

Stoke’s law is valid when the particle Reynolds number is

Answer 19

<1

Question 20

The terminal velocity of a small sphere settling in a viscous fluid varies as the
a. first power of its diameter
b. inverse of the fluid viscosity
c. inverse square of the diameter
d. square of the difference in specific weights of solid and fluid

Answer 20

B

Question 21

Buoyant force
a. for non-symmetrical bodies is not vertical
b. depends on the depth of the submergence of the floating body
c. depends on the weight of the floating body
d. none of these

Answer 21

C

Question 22

Terminal velocity is
a. constant velocity with no acceleration
b. a fluctuating velocity
c. attained after moving one-half of total distance
d. none of these

Answer 22

A

Question 23

If the radius of a basket centrifuge is halved and the rpm is doubled, then
a. linear speed of the basket is doubled
b. linear speed of the basket is halved
c. centrifugal force is doubled
d. capacity of centrifuge is increased

Answer 23

C

Question 24

Filter aid is used
a. to increase the rate of filtration
b. to decrease the pressure drop
c. to increase the porosity of the cake
d. as a support base for the septum

Answer 24

C

Question 25

The porosity of a compressible cake is
a. minimum at the filter medium
b. minimum at the upstream face
c. maximum at the filter medium
d. same throughout the thickness

Answer 25

A

Question 26

Which of the following may prove unsuitable for filtering volatile liquids?

Answer 26

Vaccum Filter