复旦大学：《大学物理——热学》课程教学资源（PPT课件）第14次课

大学物理(热学) 1) Review 2) Applications 2006-12-6 2021/9/5

2021/9/5 1 大学物理（热学） 1) Review 2) Applications 2006-12-6

4+186丁=ca e ca Weight FIGURE 19-1 Joule's experiment on the mechanical equivalent of heat H204s→(S.Sc

Heat is energy that is transferred from one bod to another because of a difference in temperature

• Heat is energy that is transferred from one body to another because of a difference in temperature

内为0 dU=dQ+dW

•dU=dQ+dW

FIGURE 19-10 The work done by a gas when its volume increases by dv A dl isdw p dk area dQ-pdv dw=F dp=-Fde =-padp=-Pdv

FIGURE 19-12 Process ADB consists of an isochoric (AD) and an isobaric(DB) process P A A nRT&(a y W=0到 Isobaric B B W=P(V3-Kk 6 =nRi(-乙 O v= Q+w

Q=0,W=0=>△(=O FIGURE 19-13 Free expansion

Molar specific heats Q=nCy AT(Cv=mc,/n) QnC∠T(CmcD/n

•Molar Specific Heats •Q=nCv⊿T (Cv=mcv/n) •Q=nCp⊿T (Cp=mcp/n)

TABLE 19-3 Specific heats of gases at 15.C Specific heats Molar specific heats cl/kg·K) (cal/mol K Cp -C y P Gas C C V P (cal/mol K) Monatomic He 0.751.15 2.98497 1.67 e 0.1480.246 2.98497 167 Diatomic 0.1770.248 4966.95 19 1.40 0.1550218503703 2.00 140 Triatomic CO 0.1530.199 680883 2.03 1.30 H2O(100C03500482 6.208.20 2.00 1.32 Polyatomic CH 0.3430.41210.301235 2.05 1.20

for the same∠T: Q=∠U(dU=dQ-PdV) Q=∠U+P∠V Q-Q=P∠V MCDAT-nCy AT=P(nR 4T/P) C=R R=1,99c4/m(K

for the same ⊿T: Qv =⊿U (dU=dQ-PdV) Qp =⊿U+P⊿V Qp -Qv=P⊿V nCp⊿T-nCv⊿T=P(nR ⊿T/P) Cp -Cv=R