Mechanical Operations
Higher is the mesh number, smaller will be the aperture size of the screen. It means that the aperture size of a 200 mesh screen will be smaller than that of 20 mesh screen. This is valid for

British standard screens
German standard screens (DIN 1171) etc
American standard screens (ASTM and Tyler standard screens)
All of these

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Mechanical Operations
Pick out the wrong statement pertaining to the roll crushers.

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

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