Figure 34.6 temprature heat of normal and conducting aluminum. The normal phase is produced below T, by application of a weak (300-gauss) magnetic tick which d superconducting but has otherwise negligible fect on the specific heat, The Debye temperature is quite high in aluminum. so the specilic hcat is dominated by the clectronic contribution throughout thi range (as can be seen from the fact that the normal-state curve is quite close to be linear). 'The discontinuity at T agrees well with the theo 34.22) ⊥h1」11 Ies-cn/c,=1,43. Well be 1.07 2.0 low T c, drops far belot resting the existence gy gap. (N, E. Phillips, Phys. Rer. 114. 676 1959)
PVEC Isothermal B PVEC Adiabatic . C FIGURE 19-8 PV diagram for adiabatic(AC) and isothermal (AB) processes on an ideal gas
PV=C PV =C
Two uses for a heat engine: a modern coal-burning power plant, and an old steam locomotive. Both produce steam which does work-on turbines to generate electricity, and on a piston that moves linkage to turn locomotive wheels The efficiency of any engine--no matter how carefully engineered-is limited by nature as described in the second law of thermodynamics. This great law is best stated in terms of a quantity called entropy, which is unlike any other. Entropy is not conserved, but instead is constrained always to increase in any real process. Entropy is a measure of disorder. The second 17 law of thermodynamics tells us that as time moves forward. the disorder in the universe increases. We also discuss many practical matters such as heat engines, heat pumps, and refrigeration CHAPTER 20
4+186丁=ca e ca Weight FIGURE 19-1 Joule's experiment on the mechanical equivalent of heat H204s→(S.Sc
瓦特 J. Watt 蒸汽机 James Watt (1736-1819)(Courtesy the E. F. Smith Collection, Van-Pelt-Dietrich Library, University of Pennsylvania)
瓦特 J. Watt 蒸汽机