0th law S.J.T.U. Phase Transformation and Applications Two systems in thermal equilibrium with a third system are also in thermal equilibrium with each other. Principle of measuring Temperature! Thermometer->the third system SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 1 First law IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 1 First law I 0th law • Two systems in thermal equilibrium with a third system are also in thermal equilibrium with each other. Principle of measuring Temperature! Thermometer -> the third system