Critical Speed (Nc) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively) ?
Correct answer: B. Nc = (1/2π). √(g/R1 - R2)
- A. Nc = (1/4π). √(g/R1 - R2)
- B. Nc = (1/2π). √(g/R1 - R2)
- C. Nc = (1/π). √(g/R1 - R2)
- D. Nc = (1/2π). √(R1 - R2/g)
Explanation
At critical speed, a ball just remains in contact with the mill wall at the top, giving Nc = (1/2π)√[g/(R1 − R2)]. Option b matches this standard formula, with the denominator understood as R1 − R2.
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