For a refrigerator,heat absorbed from the cold reservoir (sink) is $500\, J$ and heat rejected to the hot reservoir (source) is $800\, J$. The coefficient of performance is:

$A$ refrigerator works between $4^{\circ}C$ and $30^{\circ}C$. It is required to remove $600 \, cal$ of heat every second in order to keep the temperature of the refrigerated space constant. The power required is ....... $W$ (Take $1 \, cal = 4.2 \, J$)

$A$ Carnot engine,having an efficiency of $\eta = 1/10$ as a heat engine,is used as a refrigerator. If the work done on the system is $10 \ J$,the amount of energy absorbed from the reservoir at a lower temperature is ....... $J$.

$A$ refrigerator of coefficient of performance $5$ that extracts heat from the cooling compartment at the rate of $250 \ J$ per cycle is placed in a room. The heat released per cycle to the room by the refrigerator is (in $J$)

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:

What is the coefficient of performance of a refrigerator operating between $30^{\circ}C$ and $0^{\circ}C$?