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Physics of Technology PHYS 1800 Lecture 22 Introduction Section 0 Temperature Lecture 1 Slide 1 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 1 PHYSICS OF TOF ECHNOLOGY - PHYS 1800 PHYSICS TECHNOLOGY ASSIGNMENT SHEET Spring 2009Spring Assignment Sheet 2009 Date Day Lecture Chapter Feb 16 M Presidents Day 17 Tu Angular Momentum (Virtual Monday) 18 W Review 19 H Test 2 20 F* Static Fluids, Pressure Feb 23 M Flotation 25 W Fluids in Motion 27 F* Temperature and Heat Mar 2 M First Law of Thermodynamics 4 W Heat flow and Greenhouse Effect 6 F* Climate Change Mar 9-13 M-F Spring Break Mar 16 M Heat Engines 18 W Power and Refrigeration 20 F* Electric Charge Mar 23 M Electric Fields and Electric Potential 25 W Review 26 H Test 3 27 F* Electric Circuits Mar 30 M Magnetic Force Review Apr 1 W Electromagnets 3 F Motors and Generators Apr 6 M Making Waves 8 W Sound Waves 10 F* E-M Waves, Light and Color Apr 13 M Mirrors and Reflections Introduction Section 0 Lecture 1 Slide 2 15 W Refraction and Lenses 17 F* Telescopes and Microscopes Apr 20 M Review 22 W Seeing Atoms 24 F The really BIG & the really small INTRODUCTION TO Modern Physics PHYX 2710 May 1 F Final Exam: 09:30-11:20am No Class 8 5-8 5-8 9 9 9 10 10 10 No Classes 11 11 12 12 13 9-12 13 14 9-12 14 15 15 16 17 17 17 1-17 18 (not on test) 21 (not on test) Homework Due - 6 7 8 - 9 10 11 No test week 12 Fall 2004 * = Homework Handout *Homework Handout Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 2 Physics of Technology PHYS 1800 Lecture 19 Temperature Section 0 Lecture 1 Slide 3 Temperature on an Atomic Scale Introduction INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 3 Describing Motion and Interactions Position—where you are in space (L or meter) Velocity—how fast position is changing with time (LT-1 or m/s) Acceleration—how fast velocity is changing with time (LT-2 or m/s2) Force— what is required to change to motion of a body (MLT-2 or kg-m/s2 or N) Inertia (mass)— a measure of the force needed to change the motion of a body (M) Energy—the potential for an object to do work. (ML2T-2 or kg m2/s2 or N-m or J) Work is equal to the force applied times the distance moved. W = F d Kinetic Energy is the energy associated with an object’s motion. KE=½ mv2 Potential Energy is the energy associated with an objects position. Gravitational potential energy PEgravity=mgh Spring potential energy PEapring= -kx Momentum— the potential of an object to induce motion in another object (MLT-1 or kg-m/s) Introduction Section 0 Lecture 1 Slide 4 Angular Momentum and Rotational Energy— the equivalent constants of motion for rotation (MT-1 or kg/s) and (MLT-2 or kg m/s2 or N) Modern Physics PHYX 2710 Pressure— forceINTRODUCTION dividedTOby the area over which the force is applied (ML-1T-1 or kg/m-s or N/m2 or Pa) Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 4 Dennison’s Laws Thermal Poker (or How to Get a Hot Hand in Physics) • 0th Law: Full House beats Two Pairs • 1st Law: We’re playing the same game (but with a wild card) • 2nd Law: You can’t win in Vegas. • 3rd Law: In fact, you always loose. • 0th Law: Defines Temperature • 1st Law: Conservation of Energy (with heat) • 2nd Introduction Section 0 Lecture 1 Slide 5 Law: You can’t recover all heat losses (or defining entropy) INTRODUCTION TO Modern Physics PHYX 2710 • Fall 2004 3rd Law: You can never get to absolute 0. Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 5 Heat • What is heat? • What is the relationship between quantity of heat and temperature? • What happens to a body (solid, liquid, gas) when thermal energy is added or removed? Thermal Energy Solid: Atoms vibrating in all directions about their fixed equilibrium (lattice) positions. Atoms constantly colliding with each other. Liquid: Atoms still oscillating and colliding with each other but they are free to move so that the long range order (shape) of body is lost. Introduction Section 0 Lecture 1 Slide 6 Gas: No equilibrium position, no oscillations, atoms are free and move in perpetual high-speed “zig-zag” dance punctuated by collisions. solid liquid INTRODUCTION TO Modern Physics PHYX 2710 gas Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 6 Heat k BT 12 mv 2 kB is Boltzmann’s constant + + + + Lecture 1 + + Section 0 + Introduction + + =1.38 10-23 J/K Slide 7 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 7 Physics of Technology PHYS 1800 Lecture 19 Temperature Introduction Lecture 1 Slide 8 Measuring Temperature (0th Law of Thermodynamics) Section 0 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 8 What is Temperature? • If two objects are in contact with one another long enough, the two objects have the same temperature. • This begins to define temperature, by defining when two objects have the same temperature. – When the physical properties are no longer changing, the objects are said to be in thermal equilibrium. – Two or more objects in thermal equilibrium have the same temperature. – This is the zeroth law of thermodynamics. Introduction Section 0 Lecture 1 Slide 9 – Corollary: Heat flows from hot to cold (DUH!!!) INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 9 Temperature and Heat • When two objects at different temperatures are placed in contact, heat will flow from the object with the higher temperature to the object with the lower temperature. • Heat added increases temperature, and heat removed decreases temperature. • Heat and temperature are not the same. • Temperature is a quantity that tells us which direction the heat will flow. Introduction Section 0 Lecture Heat is a form of energy. (Here comes conservation of energy!!!) 1 Slide 10 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 10 • The first widely used temperature scale was devised by Gabriel Fahrenheit. • Another widely used scale was devised by Anders Celsius. • The Celsius degree is larger than the Fahrenheit degree: the ratio of Fahrenheit degrees to Celsius degrees is 180/100, or 9/5. 5 TC TF 32 9 9 TF TC 32 5 • They are both Section equal -40. Introduction 0 at Lecture 1 Slide 11 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 11 Temperature Ranges 0K Absolute zero -273.15 ºC 4.25 Liquid He boils -268.9 20.4 Liquid H boils -253 77 Liquid N2 boils -196 90 Liquid O2 boils -183 194 CO2 (dry ice) freezes -79 273 Water freezes 0 310 Body temperature ~ 37 1336 Gold melts 1063 Carbon arc 5500 Sun’s photosphere 6000 Iron Welding arc 6020 5773 Introduction Section 0 6273 6293 Lecture 1 Slide 12 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 12 Introduction Section 0 Lecture 1 Slide 13 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 13 • The zero point on the Fahrenheit scale was based on the temperature of a mixture of salt and ice in a saturated salt solution. • The zero point on the Celsius scale is the freezing point of water. • Both scales go below zero. • Is there such a thing as absolute zero? Introduction Section 0 Lecture 1 Slide 14 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 14 What is absolute zero? • • • • If the volume of a gas is kept constant while the temperature is increased, the pressure will increase. This can be used as a means of measuring temperature. A constant-volume gas thermometer allows the pressure to change with temperature while the volume is held constant. The difference in height of the two mercury columns is proportional to the pressure. Introduction Section 0 Lecture 1 Slide 15 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 15 Absolute zero • We can then plot the pressure of a gas as a function of the temperature. • The curves for different gases or amounts are all straight lines. • When these lines are extended backward to zero pressure, they all intersect at the same temperature, -273.2C. • Since negative pressure has no meaning, this suggests that the temperature can never get lower than -273.2C, or 0 K (kelvin). TK TC 273.2 Introduction Section 0 Lecture 1 Slide 16 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 16 Absolute zero and the 3rd Law of Thermodynamics • Can anything ever get colder than 0 K? • No. • Can absolute zero ever be reached? • No. TK TC 273.2 Introduction Section 0 Lecture 1 Slide 17 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 17 Physics of Technology Next Lab/Demo: Fluid Dynamics Temperature Thursday 1:30-2:45 ESLC 46 Ch 9 and 10 Next Class: Wednesday 10:30-11:20 BUS Slide 18318 room Review Ch 10 Introduction Section 0 Lecture 1 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Temperature Lecture 22 Slide 18