A cyclic process $ABCD$ is shown in the figure $P-V$ diagram. Which of the following curves represent the same process

In a cyclic process, work done by the system is

A gas takes part in two processes in which it is heated from the same initial state $1$ to the same final temperature. The processes are shown on the $P-V$ diagram by the straight line $1-2$ and $1-3$. $2$ and $3$ are the points on the same isothermal curve. $Q_1$ and $Q_2$ are the heat transfer along the two processes. Then

What is the nature of change in internal energy in the following three thermodynamical processes shown in figure

A thermodynamic process is the pressure and volumes corresponding to some points in the figure are, $P_A = 3 \times 10^4 Pa$, $V_A = 2 \times 10^{-3}\, m^3$, $P_B = 8 \times 10^4 Pa$, $V_D = 5 \times 10^{-3}\,m^3$. In process $AB, 600\, J$ of heat and in process $BC, 200\, J$ of heat is added to the system. The change in the internal energy in process $AC$ would be  …. $J$