Light Bulb Problem - Solid State Physics - Solved Paper, Exams of Solid State Physics

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NAME: 3 May 2004 Physics 112 Spring 2004 Midterm 3 Salucfity . (50 minutes =50 points) 1. Thermodynamic Identity (5 points) Write down the thermodynamic identity for the enthalpy H=U+PV What are the natural variables for H? du= du+dp Vdp 4 di= Tdt —pdv ads = TAG + Velp FMAM - H=H(O pw) 2. Light bulb problem (10 points) LZ A LOOW light bulb is left burning inside a reversible refrigerator that draws 1o0W. a) (5 points) Can the refrigerator cool below room temperature? We hove a Sthetim Qe =b/, e Th—Te = 7, awl * ve We Co Qe Geet ee Yes. b) (5 points) Justify your answer by drawing the exchanges of energy and entropy and deriving the Carnot efficiency of the retrigerator. ewtropy Gz aya, Qk hoot Theve TF ne enhrepy genoretio WwiTde | [ “n= Op aD Qu=Qes ce . amd W= Qu—Qe (BA)&. | ESSE sone we PTF arm aac of fire WoW (-%. H. Te Qe, Do kaect Wo” THE L,