Physics · Oct / Nov 2020 · Paper 42 · Question 3
0625
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The question as text
The kinetic energy of air passing through a wind turbine every minute is 720 000 J. The electrical output of the turbine is 9.0 A at a potential difference (p.d.) of 240 V. Calculate the efficiency (%) of the wind turbine. efficiency = % [5]
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(output) P = VI OR E = VIt OR E = Pt in any form words, symbols or numbers
OR (P =) VI OR (P =) 240 × 9 OR (P =) 2160 (W)
OR (E =) 240 × 9 × 60 = 129 600 (J)
(rate of energy input = 720 000 / 60 =) 12 000 (J / s)
OR energy input = 720 000 (J)
(efficiency =) (100 ×) output power / input power
OR (100 ×) output energy / input energy
words, symbols or numbers
(efficiency =) 100 × {2160 / 12 000}
(efficiency =) 18(%)
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