If $\Delta U$ and $\Delta W$ represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?

The internal energy of the gas increases In

In the following $P-V$ diagram two adiabatics cut two isothermals at temperatures $T_1$ and $T_2$ (fig.). The value of $\frac{{{V_a}}}{{{V_d}}}$ will be

For adiabatic processes $\left( {\gamma = \frac{{{C_p}}}{{{C_v}}}} \right)$