()学+(m)∫孥<0 #<(m d T SB-SA> I B0A do R&R FIGURE 20-12 The integral, ds, of the entropy for a reversible cycle is zero. Hence the difference in entropy between states a and b, SB-SA2 r dQ b- Sa= jads, is the same for path I as for path Il For isolated system:△s≥0 −  B A B A T dQ S S ( ) + ( )  0   a b T dQ b a T dQ I II    b a T dQ b a T dQ (I) (II)  −  B A B A T dQ S S R&IR For isolated system: S  0