Mechanical Operations MCQs

Question 1

Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed?

Accepted Answer

Dry grindng of large particles in un-baffed mills

Answer

Wet grinding in low viscous suspension

Answer

Wet grinding in high viscous suspension

Answer

Dry grinding of large particles (upto 1.25 cms)

Question 2

The term 'angle of nip' is concerned with the operation of the __________ crushers.

Accepted Answer

Roll

Answer

Jaw

Answer

Gyratory

Answer

None of these

Question 3

Pick out the wrong statement.

Accepted Answer

The equipment used for the removal of traces of solids from a liquid is called a classifier

Answer

Close circuit grinding is more economical than open circuit grinding

Answer

Cod oil, beef tallow or aluminium stearates are used as grinding aids in cement 'industries'

Answer

Size enlargement is a mechanical operation exemplified by medicinal tablet making

Question 4

Angle of nip of the crushing rolls does not depend upon the

Accepted Answer

Speed of the rolls

Answer

Diameter of the rolls

Answer

Product size

Answer

Feed size

Question 5

Which of the following conveyors cannot be recommended for transportation of abrasive materials?

Accepted Answer

Flight conveyor

Answer

Belt conveyor

Answer

Apron conveyor

Answer

Chain conveyor

Question 6

To get ultrafine particles, the equipment used is a

Accepted Answer

Fluid energy mill

Answer

Ball mill

Answer

Rod mill

Answer

Hammer crusher

Question 7

For a turbine agitated and baffled tank, operating at low Reynold's number (based on impeller diameter), the power number (N p ) varies with N Re as

Accepted Answer

N p ∝ $$\frac{1}{{{{	ext{N}}_{{	ext{Re}}}}}}$$

Answer

N p ∝ N Re

Answer

N p ∝ $$\sqrt {{{	ext{N}}_{{	ext{Re}}}}} $$

Answer

N p → constant

Question 8

A cottrel precipitator makes use of the __________ for dusty air cleaning.

Accepted Answer

Corrona discharge

Answer

Electric spark

Answer

Alternating current

Answer

None of these

Question 9

The mechanism of size reduction by a hammer mill is by impact and attrition between the

Accepted Answer

Both A & B

Answer

Grinding element & the housing

Answer

Feed particles

Answer

Neither A nor B