GATE 2026 AG – Question 44
For black-pepper grinding,80% of feed passes a 6 mm screen and 80% of product passes 0.5 mm. Gross energy is 10 kWh/t. Under Bond’s law, with the same feed, find the nearest energy for an 80%-passing product size of 0.2 mm, in kWh/t.
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Correct answer: (A) 18.17
Explanation
Bond’s law gives $E=K(1/\sqrt{P_{80}}-1/\sqrt{F_{80}})$. Divide the two grinding cases to cancel the constant and consistent size units:$E_2=10[(1/\sqrt{.2}-1/\sqrt6)/(1/\sqrt{.5}-1/\sqrt6)]\approx18.17$ kWh/t. The smaller product requires more energy. **A**.