815.6 A new concept: entropy I. Entropy is a state variable For a Carnot cycle Or H OuO =0 For a arbitrary quasi-static cycle gc、 O =0 or T T=0 15.6 A new concept: entropy de ri@ 十 =0 Path 1 Path 2 T P Initial state fdo rf do Path 1 0 Path 1 Path 2 Path 2 dg rsde final state I Path Path 2 Define: the differential do d= change in the entropy T15 §15.6 A new concept: entropy 1. Entropy is a state variable For a Carnot cycle: C C H H C H C H T Q T Q T T Q Q = or = + = 0 C C H H T Q T Q For a arbitrary quasi-static cycle: 0 d 0 or cycle = reversible = ∑ ∫ T Q T Q i i Initial state final state Path 1 Path 2 V P 0 d d + = ∫ ∫ i f f i T Q T Q Path 1 Path 2 0 d d − = ∫ ∫ f i f i T Q T Q Path 1 Path 2 ∫ ∫ = f i f i T Q T dQ d Path 1 Path 2 T Q S d d = Define: the differential change in the entropy §15.6 A new concept: entropy