物理与光电工程学院：《大学物理》课程PPT教学课件（讲稿，英文第三版）Chapter 17 Heat and the First Law of Thermodynamics

Chapter 17 Heat and the first law of Thermodynamics Chapter 1 7 Heat and the First Law of Thermodynamics 1. Heat and Energy Transfer, Internal Energy and Specific Heat 2. The First Law of Thermodynamics 3. Applying Ist Law of Thermodynamics 4. Molar Specific Heats for Gases, and the quipartition of energy 5. Adiabatic Expansion of a Gas

Chapter 17 Heat and the First Law of Thermodynamics Chapter 17 Heat and the First Law of Thermodynamics 1. Heat and Energy Transfer, Internal Energy and Specific Heat 2. The First Law of Thermodynamics 3. Applying 1 st Law of Thermodynamics 4. Molar Specific Heats for Gases, and the Equipartition of Energy 5. Adiabatic Expansion of a Gas

Chapter 17 Heat and the first law of Thermodynamics Heat 热量 Calorie(cal) 卡路里 Mechanical equivalent of heat热功当量 Internal energy 内能 Degrees of Freedom 自由度 diatomic molecules 双原子分子气体 monatomic molecules 单原子分子气体 polyatomic molecules 多原子分子气体 Quasi-Steady process 准静态过程

Chapter 17 Heat and the First Law of Thermodynamics Heat 热量 Calorie(Cal) 卡路里 Mechanical equivalent of heat 热功当量 Internal energy 内能 Degrees of Freedom 自由度 diatomic molecules 双原子分子气体 monatomic molecules 单原子分子气体 polyatomic molecules 多原子分子气体 Quasi-Steady Process 准静态过程

Chapter 17 Heat and the first law of Thermodynamics Isothermal( Constant-Temperature)等温 Isochoric(Constant-Volume) 等容 Isobaric( Constant-pressure 等压 Adiabatic process 绝热过程 Adiabatic Free Expansion 绝热自由膨胀 Specific heat and Molar Specific Heats 热容和摩尔热容

Chapter 17 Heat and the First Law of Thermodynamics Isothermal (Constant-Temperature) 等温 Isochoric (Constant-Volume) 等容 Isobaric (Constant-pressure) 等压 Adiabatic Process 绝热过程 Adiabatic Free Expansion 绝热自由膨胀 Specific heat and Molar Specific Heats 热容和摩尔热容

Chapter 17 Heat and the first law of Thermodynamics 817-1 Heat as Energy Transfer P404-405 I Energy and heat Heat refers to transfer of energy. Joule’ s Experiment ddl on the mechanical Falling Assess equivalent of heat weight Conclusion: a given amount of work done焦耳(Jo叫e实验 was always equivalent to a particular amount of heat input

Chapter 17 Heat and the First Law of Thermodynamics §17-1 Heat as Energy Transfer P404-405 1 Energy and heat Heat refers to a transfer of energy. Joule’s Experiment on the mechanical equivalent of heat. 焦耳(Joule)实验 1) Conclusion: A given amount of work done was always equivalent to a particular amount of heat input. Falling weight paddle

Chapter 17 Heat and the first law of Thermodynamics 2)Heat(热量Q): Heat is the energ. that is transferred between a system and its environment because of a temperature difference that exists between them. (its unit is J---Joules) O Absorbing heat: Q>0; Losing heat: Q<0 o Heat is path- dependent quantity(过程量) Heat and temperature are often confused

Chapter 17 Heat and the First Law of Thermodynamics Absorbing heat：Q>0；Losing heat：Q<0 Heat is path-dependent quantity（过程量）. 2) Heat（热量Q）： Heat is the energy that is transferred between a system and its environment because of a temperature difference that exists between them.（its unit is J---Joules） Heat and temperature are often confused

Chapter 17 Heat and the first law of Thermodynamics 3 Calorie The amount of heat necessary to raise the temperature of 1 gram of water by 1 Celsius degree. 4 Mechanical equivalent of heat In si units, the unit for heat is the joule 1 Calorie=4. 186J Example 17-1 page 405

Chapter 17 Heat and the First Law of Thermodynamics The amount of heat necessary to raise the temperature of 1 gram of water by 1 Celsius degree. 3 Calorie 1 Calorie=4.186 J In SI units, the unit for heat is the joule. 4 Mechanical equivalent of heat Example 17-1 page 405

Chapter 17 Heat and the first law of Thermodynamics 17-2817-3 Heat as Energy Transfer Internal Energy and specific Heat(404-407 在研究气体的能量时,需要确定其物理模型,这个 物理模型就是自由度。用自由度模型描写气体能量是有 局限性的,对少原子分子气体,在常温下理论值与实验 值符合得较好,但对多原子分子或在高温情况下,理论 值与实验值相差较大。这得用量子物理方法进行研究 本节我们使用自由度模型和能量均分的统计原理来研究 理想气体在常温下的气体能量

Chapter 17 Heat and the First Law of Thermodynamics 在研究气体的能量时，需要确定其物理模型，这个 物理模型就是自由度。用自由度模型描写气体能量是有 局限性的，对少原子分子气体，在常温下理论值与实验 值符合得较好，但对多原子分子或在高温情况下，理论 值与实验值相差较大。这得用量子物理方法进行研究。 本节我们使用自由度模型和能量均分的统计原理来研究 理想气体在常温下的气体能量。 17-2&17-3 Heat as Energy Transfer ; Internal Energy and Specific Heat (404-407)

Chapter 17 Heat and the first law of Thermodynamics Degrees of Freedon(自由度)p414 1自由度: 是描写物体在空间位置所需的独立坐标数 Degree of Freedom numbers of independently describing the motion of a molecule 例如:物体沿一维直线运动,最少只需一个坐标, 则自由度数为1

Chapter 17 Heat and the First Law of Thermodynamics Degrees of Freedom (自由度)p414 1自由度: 是描写物体在空间位置所需的独立坐标数。 Degree of Freedom —– numbers of independently describing the motion of a molecule. 例如：物体沿一维直线运动，最少只需一个坐标， 则自由度数为1

Chapter 17 Heat and the first law of Thermodynamics 2、自由度数目 i=t+r+y 平转振 动动动 飞机在天空中飞翔,要描写轮船在海平面上行驶,要 飞机的空间位置至少需要三描写轮船的位置至少需要 维坐标,则自由度为3。 两维坐标,则自由度为2

Chapter 17 Heat and the First Law of Thermodynamics 轮船在海平面上行驶，要 描写轮船的位置至少需要 两维坐标，则自由度为2。 飞机在天空中飞翔，要描写 飞机的空间位置至少需要三 维坐标,则自由度为 3。 2、自由度数目 i = t + r + v 平 动 转 动 振 动

Chapter 17 Heat and the first law of Thermodynamics 3质点的自由度 1)一个质点,描写它的空间位 o P(a,y, 2) 置,需要3个平动自由度=3 2)两个刚性质点 描写其质心位置需3个平动自 由度,t=3 描写其绕x、y轴转动需2个转动自 由度,绕之轴的转动能量可不计, 2 y 总自由度数 =t+r=3+2=5

Chapter 17 Heat and the First Law of Thermodynamics z y x P(x, y,z) o 2）两个刚性质点 3 质点的自由度 1） 一个质点，描写它的空间位 置，需要 3 个平动自由度， t = 3 t = 3 描写其质心位置需3个平动自 由度， 描写其绕x、y轴转动需2个转动自 由度，绕z轴的转动能量可不计， r = 2 总自由度数 i = t + r = 3 + 2 = 5 z y x o