A motor operating on 100 V draws a current of 1 A. If its efficiency is 91.6%, the source paper gives the loss of power in units of cal/s as:
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Question

A motor operating on 100 V draws a current of 1 A. If its efficiency is 91.6%, the source paper gives the loss of power in units of cal/s as:

G1 Physics · Accepted Answer

Electrical input power is P i n P_in P i ​ n = VI = 100×1 = 100 W. With efficiency 91.6%, P o u t P_out P o ​ u t = 0.916×100 = 91.6 W. Therefore the power loss is P l o s s P_loss P l ​ oss = 100-91.6 = 8.4 W. The source paper reports this numerical value as 8.4 cal/s and marks option B, without converting joule per second to calorie per second. A strict SI-to-calorie conversion would give approximately 8.4/4.2 ≈ 2 cal/s. To preserve the original paper, the Correct Answer field is kept as opti…