Practice Test: Question Set - 18
1. Specific surface area is the surface area of a unit __________ of materials.
- (A) Weight
- (B) Volume
- (C) Either (a) or (b)
- (D) Neither (a) nor (b)
2. The cumulative mass fraction of particles smaller than size dj for a collection of Ni particles of diameter di and mass mi (i = 1, 2, 3, ...... ∞) is given by
3. Ultrafine grinders operate principally by
- (A) Slow compression
- (B) Impact
- (C) Attrition
- (D) Cutting action
4. Separation of a suspension or slurry into a supernatant clear liquid (free from particles) and a thick sludge containing a high concentration of solid is called
- (A) Classification
- (B) Sedimentation
- (C) Clarification
- (D) Decantation
5. Sauter mean diameter is the same as the __________ mean diameter.
- (A) Mass
- (B) Arithmetic
- (C) Volume-surface
- (D) Geometric
6. If a force greater than that of gravity is used to separate solids & fluids of different densities, the process is termed as the
- (A) Sedimentation
- (B) Flocculation
- (C) Dispersion
- (D) Centrifugation
7. Rod mills employed for grinding
- (A) Employ a steel shell having L/D ratio of 1.5 to 3.0
- (B) Is useful for handling sticky materials
- (C) Employ steel rods of 2-12 cms diameter extending over full length of the mill
- (D) All 'a', 'b' & 'c'
8. In ball mill operation, the feed size (Df in meters) and the ball diameter (Db in metres) are related as (where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hardness))
- (A) Db2 = K.Df
- (B) Db = K.Df
- (C) Db3 = K.Df
- (D) Db2 = K.Df2
9. The ratio of the actual mesh dimension of Taylor series to that of the next smaller screen is
- (A) 2
- (B) √2
- (C) 1.5
- (D) √3
10. Crushing efficiency of a machine ranges between __________ percent.
- (A) 0.1 to 2
- (B) 5 to 10
- (C) 20 to 25
- (D) 50 to 70
11. The energy consumed by a ball mill depends on
- (A) Its speed
- (B) Its ball load
- (C) The density of the material being ground
- (D) All (a), (b) and (c)
12. Pick out the correct statement:
- (A) Removal of iron from ceramic material is necessitated (by magnetic separation method) so as to avoid discolouration of ceramic products
- (B) The operating cost of shaking screen is more than that of a vibrating screen
- (C) Screen capacity does not depend upon the specific gravity of the minerals
- (D) Asphalt is best crushed using toothed roll crusher
13. Size reduction of asbestos and mica is done by
- (A) Hammer mills
- (B) Rod mills
- (C) Gyratory crushers
- (D) Crushing rolls
14. __________ baffles are provided in ball mills.
- (A) Horizontal
- (B) No
- (C) Only two
- (D) None of these
15. In case of a hammer crusher, the final product size depends on the
- (A) Feed rate
- (B) Rotor speed
- (C) Clearance between hammer & grinding plates
- (D) All (a), (b) and (c)