AB → • Isothermal expansion (i.e. TA=TB ) • On moving A to B, volume increases and P decreases so, entropy will increase. BC → • Adiabatic expansion, so cooling occur. So TB>TC • For adiabatic process, ∆S = 0, means entropy remains same. CD → • Isothermal compression (i.e. TC=TD ) • On moving C to D, volume decreases and P increases so, entropy will decrease. DA → • Adiabatic compression, so heating occur. So TA>TD • For adiabatic process, ∆S = 0 means entropy remains same