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 the door of a refrigerator is kept open in a room,will it make the room warm or cool?

If a refrigerator's door is kept open,will the room become cool or hot? Explain.

If minimum possible work is done by a refrigerator in converting $100 \; g$ of water at $0^{\circ} C$ to ice,how much heat (in calories) is released to the surrounding at temperature $27^{\circ} C$ (Latent heat of ice $= 80 \; cal/g$)? Round to the nearest integer.

The efficiency of a Carnot engine acting as a heat engine is $\eta = 1/10$. If it is used as a refrigerator and the work done on the system is $10 \ J$,then the heat absorbed from the low-temperature reservoir is ...... $J$.

Assertion $(A)$: $A$ room can be cooled by opening the door of a refrigerator in it.
Reason $(R)$: Heat always flows from a body at higher temperature to a body at lower temperature.