Mechanical Operations Solved Questions with Answers - Set 19 - ObjectiveBooks

# Practice Test: Question Set - 19

1. To remove very small amount of tiny solid impurities from liquid, we use a
(A) Pressure filter
(B) Vacuum filter
(C) Centrifugal filter
(D) Coagulant

2. Tube mill compared to ball mill
(A) Produces finer products
(B) Is long in comparison with its diameter
(C) Uses smaller balls
(D) All (a), (b) & (c)

3. In case of a hammer crusher,
(A) Crushing takes place by impact breaking
(B) Maximum acceptable feed size is 30 cms
(C) Reduction ratio can be varied by adjusting the distance from cage to hammers
(D) All (a), (b) and (c)

4. Tabling process used for separating two materials of different densities by passing the dilute pulp over a table/deck, which is inclined from the horizontal surface at an angle of about
(A) 1 to 2°
(B) 2 to 5°
(C) 5 to 10°
(D) 10 to 15°

5. Screen efficiency is
(A) Recovery/rejection
(B) Recovery
(C) Rejection
(D) None of these

6. To get ultrafine particles, the equipment used is a
(A) Ball mill
(B) Rod mill
(C) Hammer crusher
(D) Fluid energy mill

7. Short distance transportation of grain, gravel, sand, ash, asphalt etc. is done by using a __________ conveyor.
(A) Flight
(B) Slat or drag
(C) Ribbon
(D) Screw

8. Kick's law assumes that the energy required for size reduction is proportional to the logarithm of the ratio between the initial and the final diameters. The unit of Kick's constant is
(A) kW. sec/kg
(B) kWh/kg
(C) kWh/sec. kg
(D) kg/sec

9. For a turbine agitated and baffled tank, operating at low Reynold's number (based on impeller diameter), the power number (Np) varies with NRe as
(A) Np  NRe
(B) Np  √NRe
(C) Np → constant
(D) Np  1/NRe

10. Filtration rate through a filter cake is proportional to (where, S = filtering surface = specific cake resistance μ = viscosity of the filtrate)
(A) S
(B) 1/R
(C) 1/μ
(D) All (a), (b) & (c)

11. The capacity of a classifier in 'tons of solid/hr' is given by (where, A = cross-sectional area in m2, V = rising velocity of fluid in m/sec, S = percentage of solids in the suspension by volume, ρ = density of solids in kg/m3)
(A) 3.6 AVS.ρ
(B) 3.6 A.V.ρ
(C) 3.6 A.S. ρ
(D) 3.6 AVS/ρ

12. In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as the
(A) Square root of the velocity
(B) Square of the viscosity
(C) Filtration time only
(D) Washing time only

13. Out of the following size reduction equipments, the maximum feed size can be accepted by the
(A) Tube mill
(B) Ball mill
(C) Jaw crusher
(D) Jet pulveriser

14. The sphericity of a solid particle of cubical shape is
(A) π
(B) (π/6)1/3
(C) (π/6)1/2
(D) π/3

15. During size reduction by a jaw crusher, the energy consumed decreases with the
(A) Decreasing size of product at constant size of feed
(B) Decreasing machine capacity
(C) Increasing size of feed at constant reduction ratio
(D) None of these

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