Mechanical Operations Theory MCQ Practice Paper - Set 22

Practice Test: Question Set - 22

1. A cottrell precipitator makes use of the __________ for dusty air cleaning.
    (A) Electric spark
    (B) Corona discharge
    (C) Alternating current
    (D) None of these
2. The basic filtration equation is given as dt/dV = (µ/A ∆P). [(α .CV/A) + Rm], where, V is volume of the filtrate; A is the filtration area, a is specific cake resistance, μ is viscosity of the filtrate, and C is the concentration of the solids in the feed slurry.
In a 20 minutes constant rate filtration, 5 m3 of filtrate was obtained. If this is followed by a constant pressure filtration, how much more time in minutes, it will take for another 5 m3 of filtrate to be produced? Neglect filter medium resistance, Rm; assume incompressible cake.
    (A) 10
    (B) 20
    (C) 25
    (D) 30
3. Which of the following relationships between co-efficient of friction (μ) between rock & roll and a (half of the angle of nip) of the particle to be crushed is correct?
    (A) μ > tan α
    (B) μ ≥ tan α
    (C) μ > tan 2α
    (D) μ ≤ tan α
4. Colloid mills achieve size reduction mainly by
    (A) Impact
    (B) Attrition
    (C) Cutting
    (D) Compression
5. For raschig rings, the sphericity is
    (A) 0.5
    (B) 1
    (C) < 1
    (D) √3
6. Cake resistance is
    (A) Important in the beginning of filtration
    (B) Decreased with the time of filtration
    (C) Independent of pressure drop
    (D) None of these
7. In washing type plate and frame filter press, the ratio of washing rate to the final filtrate rate is
    (A) 4
    (B) 1/4
    (C) 1
    (D) 1/2
8. A  __________ mill is a revolving mill divided into two or more sections by perforated partitions in which preliminary grinding takes place at one end and the finishing grinding at the discharge end.
    (A) Compartment
    (B) Tube
    (C) Rod
    (D) Pebble
9. Pine oil and Cresylic acid are used as __________ in the froth floatation process.
    (A) Frother
    (B) Collector
    (C) Depressor
    (D) Conditioner
10. For the preliminary breaking of hard rock, we use a
    (A) Gyratory crusher
    (B) Ball mill
    (C) Tube mill
    (D) Squirrel-cage disintegrator
11. Energy requirement (per unit mass of material crushed/ground) is highest for
    (A) Jaw crusher
    (B) Rod mill
    (C) Ball mill
    (D) Fluid energy mill
12. Pick out the wrong statement.
    (A) Close circuit grinding is more economical than open circuit grinding
    (B) Cod oil, beef tallow or aluminium stearates are used as grinding aids in cement 'industries'
    (C) The equipment used for the removal of traces of solids from a liquid is called a classifier
    (D) Size enlargement is a mechanical operation exemplified by medicinal tablet making
13. Gold ore concentration is mostly done using
    (A) Jigging
    (B) Tabling
    (C) Froth floatation
    (D) Elutriation
14. For spheres, the specific surface shape factor is given by
    (A) AD/V
    (B) D/V
    (C) A/V
    (D) √(AD/V)
15. Screw conveyors are
    (A) Run at very high rpm
    (B) Suitable for sticky materials
    (C) Suitable for highly abrasive materials
    (D) All (a), (b) and (c)
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