复旦大学《大学物理-热学》课件_第13、14次课.pdf

2021/9/51大学物理（热学）1)Review2)Heat and Temperature3)Internal Energy4)Specific Heat5)Latent Heat6)First Law7)Applications2006-11-29热学的基本内容冷热的感觉伽利略伽利略Galileo Galilei温度计的发明温度计的发明热是什么？焦焦 耳耳James Prescott Joule能量瓦特瓦特J.Watt蒸汽机用热做功存在限制否？卡卡 诺诺Sadi Carnot卡诺循环熵的引入克劳修斯R.Clausius热的微观图象？麦克斯韦麦克斯韦James Clerk Maxwell分子速度分布律玻耳兹曼玻耳兹曼Ludwig Boltzmann统计物理Heatisenergythatistransferred from one bodytoanotherbecauseofadifference in temperature.dU=dQ+dW2021/9/51大学物理（热学）1)Review2)Applications2006-12-6Heatisenergythatistransferred from one bodytoanotherbecauseofadifference in temperature.dU=dQ+dWMolar Specific HeatsQ=nCvT (Cv=mcv/n)Q=nCpT (Cp=mcp/n)for the same T:Qv=U (dU=dQ-PdV)Qp=U+PVQp-Qv=PVnCpT-nCvT=P(nR T/P)Cp-Cv=Ran ideal monatomic gas:Qv=UBecause:U=3nRT/2Thus:U=3nRT/2=nCvTOr:Cv=3R/2Adiabatic expansion:dU=dQ-PdV=-PdV(since dQ=0)on the other hand:dU=nCvT so:nCvT+PdV=0From PV=nRT,we have:PdV+VdP=nRdTand:nCv(PdV+VdP)/nR+PdV=0or:(Cv+R)PdV+CvVdP=0Since Cp=Cv+RSo:CpPdV+CvVdP=0 Or:(Cp/Cv)PdV+VdP=0Define:=Cp/CvdP/P+dV/V=0lnP+lnV=CTherefore:PV=C