The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is -20°C, the temperature of the…

29 2015 AIPMT-II ThermodynamicsRefrigerators Easy
The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is $-20^\circ C$, the temperature of the surroundings to which it rejects heat is:
A $21^\circ C$
B $31^\circ C$
C $41^\circ C$
D $11^\circ C$

Detailed Solution

$COP = \frac{T_L}{T_H - T_L}$, with $T_L = 253$ K
$5 = \frac{253}{T_H - 253} \Rightarrow T_H = \frac{6}{5}\times 253 = 303.6$ K
$T_H \approx 31^\circ C$

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