An engineer claims to have made an engine delivering $10 \, kW$ power with fuel consumption of $1 \, g \, s^{-1}$. The calorific value of the fuel is $2 \, kcal \, g^{-1}$. His claim:

Which of the following statements is correct?

Two cylinders $A$ and $B$ fitted with pistons contain equal amounts of an ideal diatomic gas at $300 \ K$. The piston of $A$ is free to move,while that of $B$ is held fixed. The same amount of heat is given to the gas in each cylinder. If the rise in temperature of the gas in $A$ is $30 \ K$,then the rise in temperature of the gas in $B$ is ..... $K$.

The figure shows the $P-V$ plot of an ideal gas taken through a cycle $ABCDA$. The part $ABC$ is a semi-circle and $CDA$ is half of an ellipse. Then,
$(A)$ the process during the path $A \rightarrow B$ is isothermal
$(B)$ heat flows out of the gas during the path $B \rightarrow C \rightarrow D$
$(C)$ work done during the path $A \rightarrow B \rightarrow C$ is zero
$(D)$ positive work is done by the gas in the cycle $ABCDA$

One mole of diatomic ideal gas undergoes a cyclic process $ABC$ as shown in the figure. The process $BC$ is adiabatic. The temperatures at $A, B$,and $C$ are $400\,K, 800\,K$,and $600\,K$ respectively. Choose the correct statement.

$A$ gas undergoes a change of state during which $100 \ J$ of heat is supplied to it and it does $20 \ J$ of work. The system is brought back to its original state through a process during which $20 \ J$ of heat is released by the gas. The work done by the gas in the second process is ....... $J$