Mechanical Operations - Study Mode

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[#191] Work index is the gross energy (kWh/tonne of feed) necessary to reduce a very large feed to such a size that 80% of product particles will pass through a 0.1 mm screen. The value of work index determined for wet grinding should be multiplied with __________ to get the same for dry grinding.

(A) 1.0

(B) 0.5

(C) 1.34

(D) 4.34

Correct Answer

(C) 1.34

[#192] The value of 'angle of nip' is generally about

(A) 16°

(B) 32°

(C) 52°

(D) 64°

Correct Answer

(B) 32°

[#193] A. __________ mill is a revolving mill divided into two or more sections by perforated partitions in which preliminary grinding takes place at one end and the finishing grinding at the discharge end.

(A) Compartment

(B) Tube

(C) Rod

(D) Pebble

Correct Answer

(A) Compartment

[#194] What is the selectivity index, if the grade of tailings & concentrate is the same?

(A) 0

(B) ∞

(C) 1

(D) 0.5

Correct Answer

(C) 1

[#195] Sphericity of raschig ring (whose length and diameter are equal) is

(A) >1

(B) <1

(C) 1

(D) 2

Correct Answer

(C) 1