A monatomic gas of n moles undergoes a cyclic process ABCDA as shown in figure. Process AB is isobaric, BC is adiabatic, CD is isochoric and DA is isothermal. The maximum and minimum temperature in the cycle are 4T0 and T0 respectively. Then
Process DA is isothermal
Further
From the graph we can see that
Further process BC is an adiabatic expansion. So, Therefore, maximum temperature is at B and minimum temperature at D or A. Hence,
In process CD:
Volume of the gas is constant and pressure is decreasing. Therefore, temperature and hence, internal energy will decrease ie., Q is negative or heat is released by the gas in the process CD.
In process AB:
Pressure is constant and volume is increasing. Therefore, temperature will also increase or Q is positive. Thus, heat is supplied to the gas only in process AB
and