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NEET PHYSICSMedium

A carnot engine having an efficiency of 110\frac{1}{10} as a heat engine, is used as a refrigerator. If the work done on the system is 10 J10\text{ J}, the amount of energy absorbed from the reservoir at lower temperature is:

A

1 J1\text{ J}

B

90 J90\text{ J}

C

99 J99\text{ J}

D

100 J100\text{ J}

Step-by-Step Solution

The efficiency of the Carnot engine is η=110\eta = \frac{1}{10}. When the same engine is used as a refrigerator, its coefficient of performance (β\beta) is given by: β=1ηη=11/101/10=9/101/10=9\beta = \frac{1 - \eta}{\eta} = \frac{1 - 1/10}{1/10} = \frac{9/10}{1/10} = 9 The coefficient of performance is also defined as the ratio of the heat absorbed from the cold reservoir (Q2Q_2) to the work done on the system (WW): β=Q2W\beta = \frac{Q_2}{W} Given that the work done on the system is W=10 JW = 10\text{ J}: 9=Q2109 = \frac{Q_2}{10} Q2=9×10=90 JQ_2 = 9 \times 10 = 90\text{ J} Therefore, the amount of energy absorbed from the reservoir at the lower temperature is 90 J90\text{ J}.

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