Mechanical Operations

51. AD5itives used for promoting the flocculation of particles is a/an

  1. Electrolyte
  2. Surface active agent
  3. Both (A) & (B)
  4. Neither (A) nor (B)

Correct answer: (C)
Both (A) & (B)

52. Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are

  1. Carbonates
  2. Sulphates
  3. Silicates & phosphates
  4. Bi-carbonates

Correct answer: (C)
Silicates & phosphates

53. All resistances during washing of cake

  1. Increases
  2. Decreases
  3. Remain constant
  4. None of these

Correct answer: (C)
Remain constant

54. Angle of nip of the crushing rolls does not depend upon the

  1. Diameter of the rolls
  2. Speed of the rolls
  3. Product size
  4. Feed size

Correct answer: (B)
Speed of the rolls

55. Apron conveyors are used for

  1. Heavy loads & short runs
  2. Small loads & long runs
  3. Heavy loads & long runs
  4. None of these

Correct answer: (A)
Heavy loads & short runs

56. Arrange the following size reduction equipment in the decreasing order of the average particle size produced by each of them.

  1. Jaw crusher, Ball mill, Fluid energy mill
  2. Ball mill, Jaw crusher, Fluid energy mill
  3. Fluid energy mill, Jaw crusher, Ball mill
  4. Fluid energy mill, Ball mill, Jaw crusher

Correct answer: (A)
Jaw crusher, Ball mill, Fluid energy mill

57. As particle size is reduced

  1. Screening becomes progressively more difficult
  2. Screening becomes progressively easier
  3. Capacity and effectiveness of the screen is increased
  4. None of these

Correct answer: (A)
Screening becomes progressively more difficult

58. As per Taggart's formula, the capacity (kg/hr) of Jaw & Gyratory crushers (for gapes of 10 to 60 cms) is equal to (where, L = Length of feed opening, cms S = Maximum width of discharge opening, cms).

  1. LS
  2. 93 LS
  3. 250 LS
  4. √(LS)

Correct answer: (B)
93 LS

59. As the product becomes finer, the energy required for grinding

  1. Decreases
  2. Increases
  3. Is same as for coarser grinding
  4. Is 1.5 times that for coarser grinding

Correct answer: (B)
Increases

60. At low Reynold's number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied:
Po = ρ/ρN3 D5: Power number
Re = ρ N D2/μ: Reynold's number
N is the impeller rotational speed, and D is the impeller diameter.

  1. Po ∝ Re-1.0
  2. Po ∝ Re0.0
  3. Po ∝ Re0.5
  4. Po ∝ Re1.0

Correct answer: (B)
Po ∝ Re0.0

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