This set of Mechanical Operations Multiple Choice Questions & Answers (MCQs) focuses on “Advantages Of Ball Mill”.

1. ____ is an open container usually cylindrical with uniform openings.
a) Bowel
b) Screen
c) Magnifier
d) Shredder

Explanation: A screen can be called as an open container usually cylindrical with uniform openings, it is normally made of wire mesh cloth.

2. What is the square opening between screens called?
a) Aperture
b) Abscissa
c) Ordinate
d) Footrope

Explanation: The size of square opening the length of clear of clear space between individual wires is called as aperture size of the screen.

3. How is screen effectiveness defined?
a) Maximum*Minimum
b) Retained*Captured
c) Recovery*Rejection
d) Retained* Rejection

Explanation: The one of the most general methods of defining classifying screens effectiveness EC is product of Recovery and Rejection.

4. In an open grinding operation, the material is passed through crusher only _____
a) Once
b) Twice
c) Not passed
d) Infinite

Explanation: Material is passed only once through the crusher in an open grinding operation, due to which less separation takes place.

5. Which of the following resides more energy?
a) Closed Circuit
b) Open circuit
c) Bi-lateral
d) By-pass

Explanation: As the material is passed only once through the crusher, the excessive formation of undersize product takes place resulting in more energy consumption.

6. In a closed grinding operation, the material is passed through crusher ____
a) Once
b) After recycle
c) After end
d) Twice

Explanation: Material is passed through the crusher several times after each and every product forms, it is send to crusher again to check the completeness of product.

7. Calculate the operating speed. If the critical speed is 35% of it and 1.05 rps?
a) 3.50
b) 10.6
c) 0.5
d) 0.36

Explanation: As operating speed = 35% of Nc = (35/100)*1.05 = 0.36 rps.

8. Given that R =400 mm and r = 0.03m, what is the critical speed?
a) 0.18
b) 0.81
c) 0.801
d) 8.1

Explanation: We know Nc = 1/2π (g/R-r)0.5 = ½*3.14 (9.81/0.4-0.03)0.5 = 0.81 rps.

9. What will be the angular velocity for a radius of 0.6 m?

Explanation: The angular velocity is wc = (g/r)1/2 = (9.81/0.6)1/2 = 4.04 rad/sec.

10. If critical speed is 55% more of operating speed and N is 0.81, what is critical speed?
a) 0.26
b) 0.81
c) 0.44
d) 1.25

Explanation: As critical = operating + 55% of operating = 0.81 + 55% of 0.81 = 1.25.

Sanfoundry Global Education & Learning Series – Mechanical Operations.

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