Question

A Carnot's engine works as a refrigerator between $250K$ and $300K$. It receives $500cal$ heat from the reservoir at the lower temperature.The amount of work done in each cycle to operate the refrigerator is:

• A. $420J$
• B. $2100J$
• C. $772J$
• D. $2520J$

Answer 1

Answer: (A)

$420J$

COP = $\frac{T_1}{T_2-T_1}=\frac{250}{300-250}=5$

$COP=5=\frac{Q_L}{W}$

$W=\frac{500\times 4.184}{5}=420J$