An ideal gas undergoes four different processes from the same initial state as shown in the figure below. Those processes are adiabatic,isothermal,isobaric and isochoric. The curve which represents the adiabatic process among $1, 2, 3$ and $4$ is

Helium gas undergoes a cycle $ABCDA$ (consisting of two isochoric and two isobaric lines) as shown in the figure. The efficiency of this cycle is nearly ....... $\%$ (Assume the gas to be an ideal gas).

Consider an engine that absorbs $130 \text{ cal}$ of heat from a hot reservoir and delivers $30 \text{ cal}$ of heat to a cold reservoir in each cycle. The engine also consumes $2 \text{ J}$ of energy in each cycle to overcome friction. If the engine works at $90 \text{ cycles per minute}$, what will be the maximum power delivered to the load (in $\text{ W}$)? [Assume the thermal equivalent of heat is $4.2 \text{ J/cal}$]

Write one process where work is converted into heat and heat is converted into work.

Suppose an ideal gas ($n$ moles) undergoes an expansion process $P = f(V)$ which passes through the point $(V_0, P_0)$. If the slope of the curve $P = f(V)$ is greater than the slope of the adiabatic curve passing through $(V_0, P_0)$,show that the gas absorbs heat at $(V_0, P_0)$.

When $Q_1$ amount of heat is supplied to a monatomic gas,the work done by the gas is $W$. When $Q_2$ amount of heat is supplied to a diatomic gas,the work done by the gas is $2W$. Then $Q_1: Q_2=$