Mechanical Operations problems
- 1. Cyclones are used primarily for separating
Options- A. solids
- B. solids from fluids
- C. liquids
- D. solids from solids Discuss
Correct Answer: solids from fluids
- 2. Molten ammonium nitrate is mixed with ground limestone in fertilizer plant in a
Options- A. pug mill
- B. mixer-extruder
- C. banbury mixer
- D. muller mixer Discuss
Correct Answer: pug mill
- 3. 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
Correct Answer: 50
- 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
Correct Answer: heavy tonnages of rocks or gravel.
- 5. 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
Correct Answer: Capacity of crusher in choke feeding is increased.
- 6. 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
Correct Answer: increases
- 7. 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
Correct Answer: specific gravities
- 8. 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. Discuss
Correct Answer: ratio of feed opening to discharge opening.
- 9. 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
Correct Answer: P/m = K .
- 10. 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
Correct Answer: impact and attrition.
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