同济大学：《大学物理》课程教学资源（电子教案，英文版）第十一章 热力学（下）

The second law ofthermodynamics

The second law of thermodynamics

Agenda Today The efficiency of heat machine The second law of thermodynamics The concept of entropy

Agenda Today • The efficiency of heat machine • The second law of thermodynamics • The concept of entropy

Reversible process and irreversible process(可逆过 程和不可逆过程) If a process is reversible: 1.No mechanical energy can be lost due to friction,or other dissipate forces that produce heat. 2.there is no heat conduction due to the temperature difference 3.the process is a quasi-static one

Reversible process and irreversible process（ 可逆过 程和不可逆过程） If a process is reversible: 1. No mechanical energy can be lost due to friction, or other dissipate forces that produce heat. 2.there is no heat conduction due to the temperature difference 3.the process is a quasi-static one

Diganta Saha Is perpetual motion machine possible?

Is perpetual motion machine possible?

Statistical interpretation of entropy 2 ②3 X◆X◆◆◆◆◆◆◆◆ 3 3 3 2 3

Statistical interpretation of entropy 2 1 3 3 2 1 1 2 3 3 1 2 1 2 3 3 1 2 2 3 1 2 1 3 1 8 1 8 3 8 3 8

Bolzmann's definition for entropy S=kIn Where k is Bolzmann's constant and is the number of microstates corresponding to the macrostate

Where k is Bolzmann’s constant and Ω is the number of microstates corresponding to the macrostate. Bolzmann’s definition for entropy

Natural process tend to move toward a state of greater disorder Maxwell's demon 巴9

Natural process tend to move toward a state of greater disorder Maxwell’s demon

The invenion of Heat machine She EXCINE r aifing Miterfookareer ly Fue piston cylin der mine s haft boiler weight cold water

The invenion of Heat machine

A useful engine exhibits two important features: 1 an engine must work in cycles 2 a cyeclic engine must include more than one thermal reservoir The efficiency of heat machine(热机效率) The ratio of the work done to the total positive heat W 9 flow provided by the 7 =1- thermal reservoir 2

A useful engine exhibits two important features: 1 an engine must work in cycles 2 a cyclic engine must include more than one thermal reservoir The efficiency of heat machine(热机效率） 1 2 1 1 Q Q Q W     The ratio of the work done to the total positive heat flow provided by the thermal reservoir