康涅狄格州大学：《普通物理》课程PPT教学课件（英文版）Lecture 23 Thermodynamics

Physics 201 Lecture 22 Thermal Physics Temperature Thermal Expansion Ideal gas law Atoms molecules and moles Kinetic Theory Reeder-05-06 Physics 201: Lecture 22, Pg 1

Reeder - 05-06 Physics 201: Lecture 22, Pg 1 Physics 201 Lecture 22 Thermal Physics Temperature Thermal Expansion Ideal Gas Law Atoms, Molecules and Moles Kinetic Theory

Thermodynamics A practical"blue-collar"science initially concerned with economics industry, real life problems DYNAMICS --Concerned with the concepts of energy transfers between a system and its environment and the resulting temperature variations Concerns itself with the physical and chemical transformations of matter in all of its forms: solid liquid, and gas Concerns the processes the "violate conservation of mechanical energy -friction Reeder-05-06 Physics 201: Lecture 22, Pg 2

Reeder - 05-06 Physics 201: Lecture 22, Pg 2 Thermodynamics A practical “blue-collar” science initially concerned with economics, industry, real life problems. DYNAMICS -- Concerned with the concepts of energy transfers between a system and its environment and the resulting temperature variations Concerns itself with the physical and chemical transformations of matter in all of its forms: solid, liquid, and gas Concerns the processes the “violate” conservation of mechanical energy -- friction ……

Temperature Zeroth Law of Thermodynamics Two objects in thermal equilibrium with each other are at the same temperature emperature is the property that determines whether or not an object is in thermal equilibrium with other objects 100°C Celsius Scale emperature of an ice-water mixture is defined as0°C This is the freezing point of water Temperature of a water-steam mixture is defined as100°c This is the boiling point of water Distance between these points is divided into 100 segments 2003 Thomson. Brooks/cole Reeder-05-06 Physics 201: Lecture 22, Pg 4

Reeder - 05-06 Physics 201: Lecture 22, Pg 4 Temperature : Zeroth Law of Thermodynamics Two objects in thermal equilibrium with each other are at the same temperature Temperature is the property that determines whether or not an object is in thermal equilibrium with other objects Celsius Scale Temperature of an ice-water mixture is defined as 0º C This is the freezing point of water Temperature of a water-steam mixture is defined as 100º C This is the boiling point of water Distance between these points is divided into 100 segments

Pressure-Temperature Graph All gases extrapolate to the same temperature at 0 pressure This temperature is absolute zero Temperature readings are nearly Kelvin Scale independent of the gas Pressure varies with temperature When the pressure of a gas when maintaining a constant volume goes to zero, its temperature is -273.15°C Trial I This temperature is called absolute zero This is the zero point of the Trial 2 Kelvin scale 273.15°C=0K Trial 3 To convert: T= Tx-27315 273.15-200-1000100200T(°C Reeder-05-06 Physics 201: Lecture 22, Pg 6

Reeder - 05-06 Physics 201: Lecture 22, Pg 6 Pressure-Temperature Graph All gases extrapolate to the same temperature at 0 pressure This temperature is absolute zero Kelvin Scale When the pressure of a gas goes to zero, its temperature is –273.15º C This temperature is called absolute zero This is the zero point of the Kelvin scale –273.15º C = 0 K To convert: TC = TK – 273.15 Temperature readings are nearly independent of the gas Pressure varies with temperature when maintaining a constant volume

Question You measure your body temperature with a thermometer calibrated in degrees Kelvin. What do you hope the reading is(assuming you are not trying to fake some sort of illness)? 1.307K 2.310K 98~37C~310k 3.313K 4.317K Reeder-05-06 Physics 201: Lecture 22, Pg 10

Reeder - 05-06 Physics 201: Lecture 22, Pg 10 Question You measure your body temperature with a thermometer calibrated in degrees Kelvin. What do you hope the reading is (assuming you are not trying to fake some sort of illness)? 1. 307 K 2. 310 K 3. 313 K 4. 317 K 98oF ~ 37oC ~ 310oK

Thermal Expansion The thermal expansion of an object is a consequence of the change in the average separation between its constituent atoms or molecules At ordinary temperatures, molecules vibrate with a small amplitude As temperature increases the amplitude increases This causes the overall object as a whole to expand Reeder-05-06 Physics 201: Lecture 22, Pg 11

Reeder - 05-06 Physics 201: Lecture 22, Pg 11 Thermal Expansion The thermal expansion of an object is a consequence of the change in the average separation between its constituent atoms or molecules At ordinary temperatures, molecules vibrate with a small amplitude As temperature increases, the amplitude increases This causes the overall object as a whole to expand

Linear Expansion For small changes in temperature The coefficient of linear expansion, a, depends on the material See table in text These are average coefficients, they can vary somewhat with temperature Reeder-05-06 Physics 201: Lecture 22, Pg 12

Reeder - 05-06 Physics 201: Lecture 22, Pg 12 Linear Expansion For small changes in temperature The coefficient of linear expansion,  , depends on the material See table in text These are average coefficients, they can vary somewhat with temperature

Area Expansion Two dimensions expand Reeder-05-06 Physics 201: Lecture 22, Pg 13

Reeder - 05-06 Physics 201: Lecture 22, Pg 13 Area Expansion Two dimensions expand

Question You are given a 4.000-cm diameter steel ball bearing and a brass plate with a 3. 994-cm diameter hole at room temperature(20C).you are asked to squeeze the steel ball through the brass plate You are allowed to increase or decrease the temperature of the two objects. However, they should both be at equal temperature at all times What can you do to succeed 2x105/°C, 1×105/°C) A. Cool the ball and the plate B. Heat the ball and the plate C. You can never succeed Reeder-05-06 Physics 201: Lecture 22, Pg 14

Reeder - 05-06 Physics 201: Lecture 22, Pg 14 Question You are given a 4.000-cm diameter steel ball bearing and a brass plate with a 3.994-cm diameter hole at room temperature (20oC). You are asked to squeeze the steel ball through the brass plate. You are allowed to increase or decrease the temperature of the two objects. However, they should both be at equal temperature at all times. What can you do to succeed? (brass = 2 x 10-5 / oC, steel = 1 x 10-5 / oC) A. Cool the ball and the plate. B. Heat the ball and the plate. C. You can never succeed

Volume Expansion Three dimensions expand For liquids only coefficient of volume expansion exists Reeder-05-06 Physics 201: Lecture 22, Pg 15

Reeder - 05-06 Physics 201: Lecture 22, Pg 15 Volume Expansion Three dimensions expand For liquids, only coefficient of volume expansion exists