2.1 Entropy as a State Function(2) S.J.T.U. Phase Transformation and Applications First Law: dLU=&O+δW dU=or+oW =0+oW For a reversible path: du =ro+Wrer 0rer =80-8W +oW Lost work -lw The difference between the work that could have been done had the process been reversible and the actual work that was done. A measure of the irreversibilities involved in the transfers of energy between the system and surroundings. =80-8h Slw =oW-8W SJTU Thermodynamics of Materials Spring 2010 ©X.J.Jin Lecture 3 Second law IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2010 © X. J. Jin Lecture 3 Second law I 2.1 Entropy as a State Function(2) First Law: dU QW dU  Qrev Wrev For a reversible path: dU Qrev Wrev QW Qrev  QWrev W Lost work lw The difference between the work that could have been done had the process been reversible and the actual work that was done. A measure of the irreversibilities involved in the transfers of energy between the system and surroundings. Qrev  Q lw lw  Wrev W