Question

The uniformity of grind of a powdered sample is indicated by which of the following index?

(A) Fineness modulus

(B) Bond's index

(C) Work index

(D) Uniformity index

Choose the correct answer from the options given below:

• (A) only.
• (D) only.
• (B) and (D) only.
• (A) and (C) only.

Hint:

Separate the four terms into those that measure grinding energy and those that measure the resulting particle size distribution.

Answer 1

The Correct Option is A

Step 1: First separate the four terms by what they actually measure. Bond's index and work index both describe the same thing, the energy required, per unit mass, to reduce a material from a large size down to a specified smaller size. They are energy consumption measures for the grinding machine, not measures of the resulting powder's particle size distribution.

Step 2: Fineness modulus is obtained from a sieve (screen) analysis of the ground sample. The cumulative percentage of material retained on each sieve of a standard series is added up and divided by 100 to give a single number.

Step 3: This single number is specifically used, by definition, as the index of the uniformity of grind of the resultant product. A lower fineness modulus indicates a finer, more uniformly ground sample, and a higher value indicates a coarser grind with more size variation.

Step 4: "Uniformity index" as worded in option (D) is not the standard, textbook term used for this purpose in agricultural process engineering, it is a distractor term that sounds plausible but does not match the recognised definition.

Since Bond's index and work index measure energy, not grind uniformity, and fineness modulus is the term specifically defined for grind uniformity, the correct answer is option 1, (A) only.