A refrigerator has a coefficient of performance of 4.2.If the refrigerator absorbs 55 cal of heat from the cold reservoir (kept at 4 $\circ$ C)in each cycle,evaluate the heat expelled into the heat reservoir (kept at 21 $\circ$ C).

Question

Quizplus · Accepted Answer

Coefficient of performance (COP) = work done/heat absorbed from cold reservoir 
COP = Q2/(Q2-Q1)  (where Q2 =heat removed from cold reservoir, Q1 =heat removed to hot reservoir )
4.2 = Q2/(Q2-21)
4.2Q2 - 88.2 = Q2
Q2 = 68.57 cal
Therefore the heat expelled into the hot reservoir is approximately 68 cal (option D).

A Refrigerator Has a Coefficient of Performance of 4 ∘\circ∘ C)in Each Cycle,evaluate the Heat Expelled into the Heat Reservoir

A Refrigerator Has a Coefficient of Performance of 4 $\circ$ C)in Each Cycle,evaluate the Heat Expelled into the Heat Reservoir