Q1: Colloid mills achieve size reduction mainly by

ANS:B - attrition

Colloid mills achieve size reduction mainly by attrition. Here's an explanation of each method:

1. Impact:
   • Size reduction by impact involves the particles colliding with each other or with the walls of the mill, resulting in fragmentation. This method is typical in hammer mills and impactors.
2. Attrition:
   • Size reduction by attrition involves the particles rubbing against each other or against the surfaces within the colloid mill. This frictional action causes the reduction in particle size. Colloid mills use this method extensively.
3. Cutting:
   • Cutting involves shearing or slicing of particles to reduce their size. Equipment like knife mills and granulators use cutting action for size reduction.
4. Compression:
   • Size reduction by compression involves applying pressure to crush or compact particles. This method is used in crushers and roll mills.