If the sink and source temperatures of a refrigerator are $4^{\circ} C$ and $15^{\circ} C$ respectively,then the efficiency of the refrigerator is:

If a refrigerator of coefficient of performance of $5$ has a freezer at a temperature of $-13^{\circ} C$,then the room temperature is (in $^{\circ} C$)

The coefficient of performance of a refrigerator working at a temperature of $27^{\circ} C$ is $5$. Find the temperature inside the refrigerator. (in $K$)

Explain the working of refrigerators/heat pumps and their coefficient of performance.

$A$ Carnot heat engine has an efficiency of $10 \%$. If the same engine is worked backward to obtain a refrigerator,then the coefficient of performance of the refrigerator is

$A$ Carnot engine having an efficiency of $1/5$ as a heat engine is used as a refrigerator. If the work done on the system is $50 \ J$,then the amount of energy absorbed from the reservoir at the lower temperature is (in $J$)