$A$ Carnot engine with sink's temperature at $17\,^{\circ}C$ has $50\%$ efficiency. By how much should its source temperature be changed to increase its efficiency to $60\%$? (in $K$)

$A$ Carnot engine $C_1$ operates between temperatures $T_1$ and $T_2$ $(T_1 > T_2)$. $A$ second Carnot engine $C_2$ uses all the heat rejected by the engine $C_1$ and operates between temperatures $T_2$ and $T_3$ (where $T_2 > T_3$). The efficiency of this combined ($C_1$ and $C_2$ together) engine is

An engine has an efficiency of $1/6$. When the temperature of the sink is reduced by $62^{\circ}C$,its efficiency is doubled. The temperature of the source is ....... $^{\circ}C$.

$A$ Carnot engine working between $400\, K$ and $800\, K$ has a work output of $1200\, J$ per cycle. The amount of heat energy supplied to the engine from the source in each cycle is ........... $J$

In a Carnot engine,if the absolute temperature of the source is $25 \%$ more than the absolute temperature of the sink,then the efficiency of the engine is (in $\%$)

The efficiency of a Carnot engine operating between reservoirs maintained at temperatures $27^{\circ}C$ and $-123^{\circ}C$ is ...... $\%$