Subtopic: Calculation of performance parameters – field capacity, efficiency, performance index, application rate and losses
Question Statement:
During field evaluation of a combine harvester, total grain collected at the grain tank was 135 kg. Amount of threshed grain found over walker and shoe were 0.65 kg and 2.4 kg, respectively. Unthreshed grain lost with straw and chaff were 4.54 kg and 0.28 kg, respectively. Threshing efficiency of the combine harvester in percent is
Options:
(A) 94.37
(B) 94.49
(C) 96.50
(D) 96.63
Official Answer Key:
D
Step-by-Step Solution & Explanation
Threshing efficiency = (grain actually threshed) / (total grain fed) × 100.
Threshed grain = grain tank + threshed grain over walker + over shoe = 135 + 0.65 + 2.4 = 138.05 kg.
Unthreshed grain = 4.54 + 0.28 = 4.82 kg.
Total grain = 138.05 + 4.82 = 142.87 kg.
η_th = 138.05/142.87 × 100 = 96.63 %.
Distractor (A) 94.37 results from using only the grain-tank quantity (135/142.87) — i.e. confusing threshing efficiency with collection/cleaning efficiency.
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