Critical speed of rotation, N (in rps – rotation per second) of a trammel is equal to (where, g = acceleration due to gravity = 9.81 m/sec2 and, r = radius of trammel, metre.) ?

Related Mcqs:

1. 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

2. Capacity of flight conveyor in tons/hr is given by (where, W & D = width and depth of flight respectively in metre V = speed of the conveyor, metre/second ρ = bulk density of material, kg/m3) ?

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

3. What is the critical rotation speed in revolutions per second, for a ball mill of 1.2 m diameter charged with 70 mm dia balls ?

   A. 0.5
   B. 1.0
   C. 2.76
   D. 0.66

4. Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed ?

   A. Wet grinding in low viscous suspension
   B. Wet grinding in high viscous suspension
   C. Dry grinding of large particles (upto 1.25 cms)
   D. Dry grinding of large particles in un-baffed mills

5. Optimum ratio of operating speed to critical speed of a trommel is_____________________?

   A. 0.33-0.45
   B. 1.33-1.45
   C. 0.5-2
   D. 1.5-2.5

6. The operating speed of a ball mill should be ______________ the critical speed?

   A. Less than
   B. Much more than
   C. At least equal to
   D. Slightly more than

7. A centrifugal filtration unit operating at a rotational speed of w has inner surface of the liquid (density ρL) located at a radial distance R from the axis of rotation. The thickness of the liquid film is δ and no cake is formed. The initial pressure drop during filtration is ___________________?

   A. ½w2 . R2 . ρL
   B. ½w2 . δ2 . ρL
   C. ½w2 . δρL (2R + δ)
   D. ½w2 . R . ρL(R + 2δ)

8. The critical speed of a trommel (N) is related to its dia D. as _____________________?

   A. N ∝ 1/√D
   B. N ∝ √D
   C. N ∝ D
   D. N ∝ 1/D

9. Critical Speed (Nc) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively) ?

   A. Nc = (1/4π). √(g/R1 – R2)
   B. Nc = (1/2π). √(g/R1 – R2)
   C. Nc = (1/π). √(g/R1 – R2)
   D. Nc = (1/2π). √(R1 – R2/g)

10. Velocity of a small particle of diameter ‘Dp’ at a distance ‘r’ from the rotational axis of a cyclone rotating at an angular speed ‘ω’ is given by (the other symbols are as per standard notation) ?

    A. [(DP/18). (ρs – ρ/μ)] ω2r
    B. [(DP2/18). (ρs – ρ/μ)] ω2r
    C. [(DP/18). (ρs – ρ/μ)] ω2r2
    D. [(DP2/18). (ρs – ρ/μ)] ω2r