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  • Question

  • Reduction ratio of crushers is the


  • Options
  • A. ratio of feed opening to discharge opening.
  • B. ratio of discharge opening to feed opening.
  • C. determining factor for minimum dia of the feed and the product.
  • D. none of these.

  • Correct Answer
  • ratio of feed opening to discharge opening. 

    • Mechanical Operations problems

    Search Results

    • 1. Ore concentration by jigging is based on the difference in the __________ of the particles.

    • Options
    • A. specific gravities
    • B. wettability
    • C. shape
    • D. none of these
      • Discuss
    • 2. As the product becomes finer, the energy required for grinding

    • Options
    • A. decreases
    • B. increases
    • C. is same as for coarser grinding
    • D. is 1.5 times that for coarser grinding
      • Discuss
    • 3. Pick out the wrong statement.

    • Options
    • A. Cummulative analysis for determining surface area is preferred over differential analysis, because of the assumption that "all particles in a simple fraction equal in size" is not needed for cummulative anslysis unlike differential anlaysis.
    • B. A gate diagram is a plot of cummulative percent by weight undersize vs. the reciprocal of diameter, in which the area beneath the curve represents the surface.
    • C. Capacity of crusher in choke feeding is increased.
    • D. Rolling of pebbles/balls from top to bottom of the heap in tumbling mills is called 'cascading and throwing of the balls through the air to the toe of the heap is called 'cataracting'.
      • Discuss
    • 4. Reciprocating screens are normally inclined at an angle of 5° with the horizontal and employ gyratory motion at feed end & reciprocating motion at the discharge end. They are not suitable for the screening of the

    • Options
    • A. light metal powder down upto 4 meshsize.
    • B. dry chemicals.
    • C. heavy tonnages of rocks or gravel.
    • D. powdered food & granular materials.
      • Discuss
    • 5. In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill.

    • Options
    • A. 35
    • B. 50
    • C. 70
    • D. 85
      • Discuss
    • 6. Which of the following equations is Rittinger's crushing law? (where P = power required by the machine, m = feed rate, k = a constant = volume surface mean diameter of feed & product respectively.)

    • Options
    • A. P/m = K/Dp
    • B. P/m = K . ln
    • C. P/m = K .
    • D. none of these.
      • Discuss
    • 7. General mechanism of size reduction in intermediate and fine grinder is by

    • Options
    • A. cutting action.
    • B. compression.
    • C. compression and tearing.
    • D. impact and attrition.
      • Discuss
    • 8. Which of the following gives the crushing energy required to create new surface?

    • Options
    • A. Taggarts rule
    • B. Fick's law
    • C. Rittinger's law
    • D. none of these
      • Discuss
    • 9. In bag filters, filter fabrics are never made of

    • Options
    • A. metallic wire woven mesh
    • B. polyester fibres
    • C. cotton fibres
    • D. nylon fibres
      • Discuss
    • 10. Separation of isotopes is generally done using a/an __________ centrifuge.

    • Options
    • A. ultra
    • B. disk-bowl
    • C. both (a) & (b)
    • D. neither (a) nor (b)
      • Discuss

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