The first law of thermodynamics confirms the law of _____

One mole of an ideal diatomic gas undergoes a transition from $A$ to $B$ along a path $AB$ as shown in figure. The change in internal energy of the gas during the transition is

An ideal gas is taken from state-$1$ to state-$2$ through optional path $A, B, C$ and $D$ as shown in the $P-V$ diagram. Let $Q, W$ and $U$ represent the heat supplied, work done and change internal energy respectively, then

A system goes from $A$ to $B$ via two processes $I$ and $\mathrm{II}$ shown in the figure. If $\Delta U_1$ and $\Delta U_2$ are the changes in internal energies in the processes I and Il respectively