The reduction ratio for grinders is defined as (where, Df and Dp are average diameters of feed and product respectively) ?

Related Mcqs:

1. According to Bond crushing law, the work required to form particle of size ‘D’ from very large feed is (where (S/V)p and (S/V)f are surface to volume ratio of the product and feed respectively) ?

   A. (S/V)p
   B. √(S/V)p
   C. (S/V)2p
   D. (S/V)f

2. The reduction ratio for fine grinders is_____________?

   A. 5-10
   B. 10-20
   C. 20-40
   D. As high as 100

3. Which of the following equations is Rittinger’s crushing law? (Where P = power required by the machine, m = feed rate, k = a constant, D̅ sa & D̅ sb = volume surface mean diameter of feed & product respectively) ?

   A. P/m = K/ √Dp
   B. P/m = K . ln D̅ sa/D̅ sb
   C. P/m = K . (1/ D̅ sb – 1/D̅ sa)
   D. None of these

4. Half the angle of nip, (α), for a roll crusher is given by (where, dr, dp and df are diameters of crushing rolls, feed particles and rolls gap respectively) ?

   A. cos α = (dr + dp)/(dr + df)
   B. cos α = (dr + df)/(dr + dp)
   C. tan α = (dr + dp)/(dr + df)
   D. sin α = (dr + dp)/(dr + df)

5. The main size reduction operation in ultrafine grinders is_____________?

   A. Cutting
   B. Attrition
   C. Compression
   D. Impact

6. What is the reduction ratio in a fine crushing operation having following feed and product sizes ?

   A. 0.5
   B. 2
   C. 5
   D. 10

7. Kick’s law assumes that the energy required for size reduction is proportional to the logarithm of the ratio between the initial and the final diameters. The unit of Kick’s constant is_________________?

   A. kW. sec/kg
   B. kWh/kg
   C. kWh/sec. kg
   D. kg/sec

8. 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

9. Which of the following achieves the least reduction ratio for a given feed size ?

   A. Jaw crusher
   B. Roll crusher
   C. Cone crusher
   D. Gyratory crusher

10. In a size reduction crushing operation, feed size is 100 to 300 mm. while the product size is 10 to 50 mm. This is a case of the _____________ crushing?

    A. Primary
    B. Secondary
    C. Fine
    D. Ultrafine