Application of Rittinger's Law for Comminution Energy:

• Formula: Rittinger's law states that energy required for size reduction is directly proportional to the newly created surface area, which is inversely proportional to particle diameter:
  $$E = K_R \left(\frac{1}{D_2} - \frac{1}{D_1}\right)$$
• Step 1: Find constant $K_R$ from the first reduction:
  $D_1 = 10\text{ mm}$, $D_2 = 5\text{ mm}$, $E = 1\text{ kJ/kg}$
  $$1 = K_R \left(\frac{1}{5} - \frac{1}{10}\right) = K_R (0.2 - 0.1) = 0.1 K_R \implies K_R = 10\text{ kJ}\cdot\text{mm/kg}$$
• Step 2: Compute energy $E_2$ for reduction from $D_1' = 1\text{ mm}$ to $D_2' = 0.5\text{ mm}$:
  $$E_2 = K_R \left(\frac{1}{0.5} - \frac{1}{1}\right) = 10 \times (2 - 1) = 10 \times 1 = 10\text{ kJ/kg}$$

Assertion (A) is true: excessive feeding overloads the rotating plates, causing power surges, motor stalling, and unevenly coarse ground product. Reason (R) is true: grinding fineness in burr/attrition mills is governed by the plate surface corrugations and the axial clearance gap between plates. However, (R) does not explain why overfeeding degrades performance (overfeeding degrades performance due to inadequate energy transfer and plate separation). Hence (R) is NOT the correct explanation of (A). Option analysis: (A) (R) does not explain the overfeeding mechanism. (B) Both (A) and (R) are true but (R) is NOT the correct explanation of (A). (C) (R) is true. (D) (A) is true.