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

$A$ Carnot engine has an efficiency of $50 \%$. If the temperature of the sink is reduced by $40 \, K$,its efficiency increases by $30 \%$. The temperature of the source will be $.... \, K$.

In the $1^{\text{st}}$ case,a Carnot engine operates between temperatures $300 \, K$ and $100 \, K$. In the $2^{\text{nd}}$ case,as shown in the figure,a combination of two engines is used. The efficiency of this combination (in the $2^{\text{nd}}$ case) will be:

For which of the following options will the efficiency of a Carnot engine be the highest?

Consider a reversible engine of efficiency $\frac{1}{6}$. When the temperature of the sink is reduced by $62^{\circ} C$, its efficiency gets doubled. The temperature of the source and sink respectively are

$A$ reversible engine and an irreversible engine are working between the same temperatures. The efficiency of the ...........