HeatLectures

HeatLectures - Lectures on Heat and Thermodynamics Physics...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Lectures on Heat and Thermodynamics Physics 152 Michael Fowler, University of Virginia 8/30/08 Contents HEAT. .......................................................................................................................................................... 3 Feeling and seeing temperature changes. .................................................................................... 3 Classic Dramatic Uses of Temperature-Dependent Effects. ......................................................... 4 The First Thermometer. ....................................................................................................................... 5 Newton’s Anonymous Table of Temperatures . .............................................................................. 7 Fahrenheit’s Excellent Thermometer . .............................................................................................. 7 Amontons’ Air Thermometer: Pressure Increases Linearly with Temperature . ............................ 7 Thermal Equilibrium and the Zeroth Law of Thermodynamics. ..................................................... 8 Measuring Heat Flow: a Unit of Heat. .............................................................................................. 8 Specific Heats and Calorimetry . ...................................................................................................... 9 A Connection With Atomic Theory . ............................................................................................... 10 Latent Heat. ...................................................................................................................................... 11 THERMAL EXPANSION AND THE GAS LAW. ............................................................................................ 12 Coefficients of Expansion. ............................................................................................................... 12 Gas Pressure Increase with Temperature. ..................................................................................... 13 Finding a Natural Temperature Scale. ........................................................................................... 13 The Gas Law . .................................................................................................................................... 14 Avogadro’s Hypothesis. ................................................................................................................... 15 EARLY ATTEMPTS TO UNDERSTAND THE NATURE OF HEAT . .................................................................... 16 When Heat Flows, What, Exactly is Flowing? . ............................................................................... 16 Lavoisier’s Caloric Fluid Theory . ...................................................................................................... 16 The Industrial Revolution and the Water Wheel . .......................................................................... 17 Measuring Power by Lifting. ............................................................................................................ 18 Carnot’s Caloric Water Wheel . ...................................................................................................... 18 How Efficient are these Machines? . .............................................................................................. 19 Count Rumford. ................................................................................................................................ 20 Rumford’s Theory of Heat. ............................................................................................................... 22 THE DISCOVERY OF ENERGY CONSERVATION: MAYER AND JOULE . ................................................... 24 Robert Mayer and the Color of Blood. .......................................................................................... 24 James Joule. ..................................................................................................................................... 26 But Who Was First: Mayer or Joule? . .............................................................................................. 27 The Emergence of Energy Conservation . ..................................................................................... 27 KINETIC THEORY OF GASES: A BRIEF REVIEW. ........................................................................................ 28
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Bernoulli's Picture. ............................................................................................................................. 28 The Link between Molecular Energy and Pressure . ..................................................................... 29 Maxwell finds the Velocity Distribution . ......................................................................................... 30 Velocity Space. ................................................................................................................................ 31 Maxwell’s Symmetry Argument. ..................................................................................................... 32 What about Potential Energy?. ...................................................................................................... 37 Degrees of Freedom and Equipartition of Energy . ...................................................................... 39 Brownian Motion . ............................................................................................................................. 39 IDEAL GAS THERMODYNAMICS: SPECIFIC HEATS, ISOTHERMS, ADIABATS. ......................................... 39 Introduction: the Ideal Gas Model, Heat, Work and Thermodynamics. ................................... 39 The Gas Specific Heats C V and C P ................................................................................................. 40 Tracking a Gas in the (P, V) Plane: Isotherms and Adiabats . ..................................................... 42 Equation for an Adiabat . ................................................................................................................ 44 HEAT ENGINES: THE CARNOT CYCLE . .................................................................................................... 46 The Ultimate in Fuel Efficiency . ....................................................................................................... 46 Step 1: Isothermal Expansion . ......................................................................................................... 47 Step 2: Adiabatic Expansion. .......................................................................................................... 48 Steps 3 and 4: Completing the Cycle . .......................................................................................... 49 Efficiency of the Carnot Engine . .................................................................................................... 51 THE LAWS OF THERMODYNAMICS AND LIMITS ON ENGINE EFFICIENCY. ............................................ 53 The Laws of Thermodynamics. ........................................................................................................ 53 How the Second Law Limits Engine Efficiency . ............................................................................ 55 A NEW THERMODYNAMIC VARIABLE: ENTROPY . .................................................................................. 57 Introduction . ..................................................................................................................................... 57 Heat Changes along Different Paths from a to c are Different! . ............................................... 57 But Something Heat Related is the Same: Introducing Entropy. ................................................ 59 Finding the Entropy Difference for an Ideal Gas. ......................................................................... 61 Entropy in Irreversible Change: Heat Flow Without Work. ........................................................... 62 Entropy Change without Heat Flow: Opening a Divided Box. ................................................... 62 The Third Law of Thermodynamics. ................................................................................................ 64 ENTROPY AND THE KINETIC THEORY: THE MOLECULAR PICTURE . ......................................................... 64 Searching for a Molecular Description of Entropy. ...................................................................... 64 Enter the Demon. ............................................................................................................................. 65 Boltzmann Makes the Breakthrough. ............................................................................................. 66 Epitaph: S = k ln W. ........................................................................................................................... 68 But What Are the Units for Measuring W ? . ................................................................................... 68 A More Dynamic Picture. ................................................................................................................ 68 The Removed Partition: What Are the Chances of the Gas Going Back?. .............................. 69 Demon Fluctuations. ........................................................................................................................ 70 Entropy and “Disorder”. ................................................................................................................... 71 Summary: Entropy, Irreversibility and the Meaning of Never. ..................................................... 71 Everyday Examples of Irreversible Processes. ............................................................................... 72 MOLECULAR COLLISIONS. ...................................................................................................................... 73 Difficulties Getting the Kinetic Theory Moving.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/07/2011 for the course PHYSICS 152 taught by Professor Michaelfowler during the Fall '07 term at UVA.

Page1 / 89

HeatLectures - Lectures on Heat and Thermodynamics Physics...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online