Engineering Questions with Answers - Multiple Choice Questions

Mechanical Operations MCQ’s – Ball Mill

1 - Question

What is the average particle size of ultra-fine grinders?
a) 1 to 20 µm
b) 4 to 10 µm
c) 5 to 200 µm
d) 50 to 100 µm

View Answer

Answer: a
Explanation: The particle averaging 1 to 2 µm in size with substantially all particles through a standard 325 mesh screen.

2 - Question

Which of the following uses impact and attrition?
a) Ball mill
b) Tumbling mill
c) Ultra-fine grinders
d) Hammer mill

View Answer

Answer: c
Explanation: Grinding takes place due to impact and attrition, it consists set of swing hammers, rotor, classifier wheels and fan wheels.

3 - Question

What is the feed size for a Ultra-Fine grinder?
a) > 34 inches
b) < 34 inches
c) > 12 inches
d) < 12 inches

View Answer

Answer: b
Explanation: The feed size of ultra-fine grinder is less than 34 inches and the product sizes between 1 to 20 micro meter passing through 100 mesh.

4 - Question

The fluid energy mill involves __________
a) Pressure
b) Temperature
c) Fluid
d) Density

View Answer

Answer: a
Explanation: The fluid energy mill usually uses compressed air and super-heated steam admitted at a pressure of 7 atm through nozzles

5 - Question

At what speed stirred mill operates?
a) 50 to 500 rpm
b) 5 to 10 rpm
c) 10 to 500 rpm
d) 100 to 1500 rpm

View Answer

Answer: d
Explanation: In a stirred mill, a central paddle wheel or impellor armature stirs the media at speed from 100 to 1500 rpm.

6 - Question

What does colloid mill produces?
a) Emulsions and Solid dispersions
b) Wet and dry products
c) Coarse and fine particles
d) Broad particles

View Answer

Answer: a
Explanation: Colloidal suspensions, emulsions and solid dispersions are produced by means of colloid mills or dispersions mills.

7 - Question

The clearance between rotor and stator is ______
a) 5 to 10 mm
b) 1 to 2.5 mm
c) 0 to 1.25 mm
d) 5 to 15 mm

View Answer

Answer: c
Explanation: The mill consists of a flat rotor and stator, the clearance between the rotor and stator is generally 1 to 1.25 mm.

8 - Question

The power consumption of colloid mill is _______
a) Very low
b) Optimum
c) Critical
d) Very high

View Answer

Answer: d
Explanation: The power consumption is very high and the material should therefore be ground as fine as possible before it is fed to mill.

9 - Question

The speed of a rotary knife cutter is ___
a) 100 to 500 rev/min
b) 200 to 900 rev/min
c) 400 to 600 rev/min
d) 50 to 60 rev/min

View Answer

Answer: c
Explanation: A rotary knife cutter contains a horizontal rotor turning at 200 to 900 revolutions per minute, which is cylindrical chamber

10 - Question

______ indicates the impact of resistance.
a) Toughness
b) Rigidity
c) Brittleness
d) Fatigue

View Answer

Answer: a
Explanation: Toughness indicates the impact of resistance. It is the inverse of friability and brittleness, it is also a deciding factor for commutation.

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