Energy requirement (per unit mass of material crushed/ground) is highest for__________________?

Related Mcqs:

1. Rittinger’s number designates the new surface created per unit mechanical energy absorbed by the material being crushed. Larger value of Rittinger’s number of a material indicates its________________?

   A. Easier grindability
   B. Poor grindability
   C. High power consumption in grinding
   D. None of these

2. Rittinger number which designates the new surface produced per unit of mechanical energy absorbed by the material being crushed, depends on the ______________________?

   A. State or manner of application of the crushing force
   B. Ultimate strength of the material
   C. Elastic constant of the material
   D. All A., B. and C.

3. The energy required per unit mass to grind limestone particles of very large size to 100 μm is 12.7 kWh/ton. An estimate (using Bond’s law) of the energy to grind the particles from a very large size to 50 μm is________________?

   A. 6.35 kWh/ton
   B. 9.0 kWh/ton
   C. 18 kWh/ton
   D. 25.4 kWh/ton

4. Theoretical capacity of crushing rolls in tons/hr is given by (where, V = peripheral velocity, m/sec. W = width of rolls, m Dr = distance between rolls ρ = density of material to be crushed, kg/m3 here, V =πND where, N = speed of the rolls in rotation per second (rps) D = diameter of rolls, m) ?

   A. 3.6 V.W.Dr.ρ
   B. 3.6 V.W. ρ
   C. 3.6 W.Dr.ρ
   D. 3.6 V.W.Dr/ρ

5. The optimum moisture content in solids to be crushed/ground ranges from _______________ percent?

   A. 3 to 4
   B. 8 to 10
   C. 10 to 15
   D. 15 to 20

6. Number of particles in a crushed solid sample is given by (where, m = mass of particles in a sample, Vp = volume of one particle, ρ= density of particles) ?

   A. m/ρ . Vp
   B. m . ρ/Vp
   C. m . Vp/ρ
   D. Vp/m . ρ

7. The crushed material received for separation is called feed or_________________?

   A. Tailing
   B. Heading
   C. Concentrate
   D. Middling

8. The material is crushed in a gyratory crusher by the action of__________________?

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

9. Which of the following relationships between co-efficient of friction (μ) between rock & roll and a (half of the angle of nip) of the particle to be crushed is correct ?

   A. μ > tan α
   B. μ ≥ tan α
   C. μ > tan 2α
   D. μ ≤ tan α

10. Limestone is normally crushed in a _____________________?

    A. Roll crusher
    B. Hammer crusher
    C. Ball mill
    D. Tube mill