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The coefficient of performance of a refrigerator is 55. If the temperature inside freezer is 20C-20^\circ\text{C}, the temperature of the surroundings to which it rejects heat is

A

31C31^\circ\text{C}

B

41C41^\circ\text{C}

C

11C11^\circ\text{C}

D

21C21^\circ\text{C}

Step-by-Step Solution

The coefficient of performance (β\beta) of a refrigerator is given by the formula: β=T2T1T2\beta = \frac{T_2}{T_1 - T_2} where T2T_2 is the absolute temperature of the cold reservoir (freezer) and T1T_1 is the absolute temperature of the hot reservoir (surroundings). Given: β=5\beta = 5 T2=20C=27320=253 KT_2 = -20^\circ\text{C} = 273 - 20 = 253\text{ K} Substituting these values into the formula: 5=253T12535 = \frac{253}{T_1 - 253} 5(T1253)=2535(T_1 - 253) = 253 5T11265=2535T_1 - 1265 = 253 5T1=15185T_1 = 1518 T1=15185=303.6 KT_1 = \frac{1518}{5} = 303.6\text{ K} Converting T1T_1 back to Celsius: T1(C)=303.6273=30.6C31CT_1 (^\circ\text{C}) = 303.6 - 273 = 30.6^\circ\text{C} \approx 31^\circ\text{C} Therefore, the temperature of the surroundings is nearly 31C31^\circ\text{C}.

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