When the absolute temperature of the source of a Carnot heat engine is increased by $25 \%$,its efficiency increases by $80 \%$. The new efficiency of the engine is (in $\%$)

$A$ Carnot engine operating between temperatures $600 \,K$ and $300 \,K$ absorbs $800 \,J$ of heat from the source. The mechanical work done per cycle is (in $\,J$)

$A$ Carnot engine operates between $627^{\circ}C$ and $227^{\circ}C$. The efficiency of the Carnot engine is ....... $\%$

The temperature of food material in a refrigerator is $4^{\circ} C$ and the temperature of the environment is $15^{\circ} C$. If a Carnot cycle is used in its working gas,find its Carnot efficiency.

$A$ Carnot engine with efficiency $50 \%$ takes heat from a source at $600 \ K$. To increase the efficiency to $70 \%$,keeping the temperature of the sink same,the new temperature of the source will be (in $K$)

$A$ heat engine receives $200 \, cal$ of heat and rejects $150 \, cal$ of heat. If the temperature of the source is $400 \, K$,what is the temperature of the sink in $K$ (in $, K$)?