Final answer:
The coefficient of performance of the refrigerator is calculated as the ratio of the heat removed from the cold reservoir to the work done, which gives a value of 1.0.
Step-by-step explanation:
The student has asked what the coefficient of performance of a refrigerator is when it takes in 20 joules of work and exhausts 40 joules of heat.
The coefficient of performance (COP) for a refrigerator is defined as the ratio of the heat removed from the cold reservoir (Qc) to the work (W) done:
COP = Qc / W
In this case, the heat removed from the cold reservoir (Qc) would be the difference between the heat exhausted to the hot reservoir (Qh) and the work input:
Qc = Qh - W = 40 J - 20 J = 20 J
Therefore:
COP = Qc / W = 20 J / 20 J = 1.0.
The refrigerator's coefficient of performance is 1.0.