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Mechanical Operations MCQ Questions & Answers

Mechanical Operations MCQs : This section focuses on the "Mechanical Operations". These Multiple Choice Questions (MCQs) should be practiced to improve the Mechanical Operations skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

Solid particles separation based on the difference in their flow velocities through fluids is termed as the

A. clarification
B. classification
C. elutriation
D. sedimentation

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Question 2

Size reduction of the __________ can be suitably done by ball mills, crushing rolls and rod mills.

A. metalliferrous ores
B. non-metallic ores
C. basic slags
D. asbestos & mica

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Question 3

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

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Question 4

Size reduction of __________ is accomplished in steam heated rollers and roll crushers.

A. resins
B. gums
C. hard rubber
D. waxes

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Question 5

For a non-spherical particle, the sphericity

A. is defined as the ratio of surface area of a sphere having the same volume as the particle to the actual surface area of the particle.
B. has the dimension of length.
C. is always less than 1.
D. is the ratio of volume of a sphere having the same surface area as the particle to the actual volume of the particle.

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Question 6

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

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Question 7

Range of compressibility co-efficient of the commercial compressible cake obtained in filtration operation is

A. 0.01 to 0.1
B. 0.1 to 0.3
C. 0.2 to 0.8
D. 0.2 to 0.4

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Question 8

__________ centrifuge is normally used in sugar mills.

A. Tubular bowl
B. Disc-bowl
C. Suspended batch basket
D. Perforated horizontal basket continuous

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Question 9

Which of the following mineral dressing operations is termed as 'comminution'?

A. Panning
B. Spiralling
C. Tabling
D. None of these

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Question 10

Which of the following is not an ultrafine grinder (colloid mill)?

A. Micronizers
B. Agitated mills and fluid energy mills
C. Toothed roll crusher
D. Hammer mills with internal classification

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Question 11

Which of the following relationships between co-efficinet 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

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Question 12

__________ is the most commonly used 'filter aid'.

A. Diatomaceous earth
B. Fuller's earth
C. Vermiculite
D. Semi-plastic clay

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Question 13

In washing type plate and frame filter press, the ratio of washing rate to the final filtrate rate is

A. 4
B. 01-Apr
C. 1
D. 01-Feb

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Question 14

Highly viscous liquids & pastes are agitated by

A. propellers
B. turbine agitators
C. multiple blade paddles
D. none of these

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Question 15

Equivalent diameter of a particle is the diameter of the sphere having the same

A. ratio of surface to volume as the actual volume.
B. ratio of volume to surface as the particle.
C. volume as the particle.
D. none of these.

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Question 16

Ball mills and tube mills with flint or porcelain balls are used for size reduction of

A. asbestos
B. rubber
C. non-metallic ores
D. limestone

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Question 17

The capacity of a pneumatic conveying system depends upon the

A. bulk density of materials.
B. pressure of the conveying air.
C. diameter of the conveying line.
D. all (a), (b) and (c).

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Question 18

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.

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Question 19

The distribution given by microscopic analysis of powder is

A. number
B. length
C. area
D. volume

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Question 20

If dp is the equivalent diameter of a non-spherical particle, Vp its volume and sp its surface area, then its sphericity is Φs is defined by

A. Φs = 6 Vp/dp sp
B. Φs = Vp/dp sp
C. Φs = 6 dp Sp/Vp
D. Φs = dp Sp/Vp

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Question 21

Pebble mills are tumbling mills widely used for grinding in the manufacture of paints & pigments and cosmetic industries, where iron contamination in the product is highly objectionable. Pebbles used in pebble mill are made of

A. bronze
B. stainless steel
C. flint or porcelain
D. concrete

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Question 22

Which of the following is a pressure filter ?

A. Leaf filter (Moore filter).
B. Plate and flame filter.
C. Rotary drum filter.
D. Sand filter.

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Question 23

The capacity of a belt conveyor depends upon two factors. If one is the cross-section of the load, the other is the __________ of the belt.

A. speed
B. thickness
C. length
D. none of these

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Question 24

Pick out the wrong statement.

A. Recycled coarse material to the grinder by a classifier is termed as circulating load.
B. Wear and tear in wet crushing is more than that in dry crushing of materials.
C. Size enlargement (opposite of size reduction) is not a mechanical operation.
D. A 'dust catcher' is simply an enlargement in a pipeline which permits the solids to settle down due to reduction in velocity of the dust laden gas.

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Question 25

The main size reduction operation in ultrafine grinders is

A. cutting
B. attrition
C. compression
D. impact

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Question 26

Power required to drive a ball mill with a particular ball load is proportional to (where, D = diameter of ball mill )

A. D
B. 1/D
C. D2.5
D. 1/D2.5

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Question 27

Gravity settling process is not involved in the working of a

A. hydrocyclone
B. classifier
C. dorr-thickener
D. sedimentation tank

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Question 28

Which of the following is the most suitable for handling fibrous and dense slurries ?

A. Propeller agitator
B. Cone type agitator
C. Turbine agitator
D. Radial propeller agitator

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Question 29

Diatomaceous earth is a/an

A. explosive
B. filter aid
C. filter medium
D. catalyst

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Question 30

Filter aids like asbestos, kieselguhr, diatomaceous earth etc. are used to increase the porosity of the final filter cake & reducing the cake resistance during filtration. Filter aid is

A. added to the feed slurry.
B. precoated on the filter medium prior to filtration.
C. separated from the cake by dissolving solids or by burning it off.
D. all 'a', 'b'&'c'.

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Question 31

For sizing of fine materials, the most suitable equipment is a

A. trommel
B. grizzly
C. shaking screen
D. vibrating screen

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Question 32

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).

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Question 33

200 mesh screen means 200 openings per

A. cm2
B. cm
C. inch
D. inch2

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Question 34

Froth floatation is the most suitable for treating

A. iron ores
B. sulphide ores
C. quartzite
D. none of these

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Question 35

Two particles are called to be equal settling, if they are having the same.

A. size.
B. specific gravity.
C. terminal velocities in the same fluid & in the same field of force.
D. none of these.

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Question 36

The energy required per unit mass to grind limestone particles of very large size to 100 μm is 12.7 kWh/ton. An estimate (using Bond's law) of the energy to grind the particles from a very large size to 50 μrn is

A. 6.35 kWh/ton
B. 9.0 kWh/ton
C. 18 kWh/ton
D. 25.4 kWh/ton

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Question 37

Which of the following is the most suitable for cleaning of fine coal dust (<0.5 mm) ?

A. Trough washer
B. Baum jig washer
C. Spiral separator
D. Froth floatation

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Question 38

Jigging is a technique by which different particles can be

A. separated by particle size.
B. separated by particle density.
C. separated by particle shape.
D. mixed.

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Question 39

Balls for ball mills are never made of

A. forged/cast steel
B. lead
C. cast iron
D. alloy steel

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Question 40

Crushing of mineral particles is accomplished in a 'cage mill', when one or more alloy steel bars are revolved in opposite directions. It is a type of __________ mill.

A. impact
B. roll
C. vibratory
D. none of these

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Question 41

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.

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Question 42

Which of the following is not a part of the Blake jaw crusher?

A. Hanger
B. Check plates
C. Toggles
D. Pitman

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Question 43

Pick out the wrong statement pertaining to the roll crushers.

A. Maximum feed size determines the required roll diameter.
B. For hard material's crushing, the reduction ratio should not exceed 4.
C. Both the rolls run necessarily at the same speed.
D. Reduction ratio and differential roll speed affect production rate & energy consumed per unit of surface produced.

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Question 44

Tabular bowl centrifuges as compared to disk bowl centrifuges

A. operate at higher speed.
B. employ bowl of larger diameter.
C. can not be operated under pressure/vacuum.
D. can't be used for separation of fine suspended solids from a liquid.

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Question 45

Filter aid is used to

A. increase the rate of filtration.
B. decrease the pressure drop.
C. increase the porosity of the cake.
D. act as a support base for the septum.

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Question 46

Number of particles in a crushed solid sample is given by (where, m = mass of particles in a sample, Vp = volume of one particle, ρ= density of particles)

A. m/ρ . Vp
B. m . ρ/Vp
C. m . Vp/ρ
D. Vp/m . ρ

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Question 47

The value of 'angle of nip' is generally about

A. 16°
B. 32°
C. 52°
D. 64°

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Question 48

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.

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Question 49

Sulphuric acid mist is arrested by using a __________ scrubber.

A. packed wet
B. hollow wet
C. venturi
D. co-current

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Question 50

Which of the following is not categorised as a "mechanical operation" ?

A. Agitation
B. Filtration
C. Size enlargement
D. Humidification

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