Temperature Introduction Section 0 Lecture 1 Slide 1 Lecture 22 Slide 1 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Physics of Technology PHYS 1800 Lecture 22 Temperature

Introduction Section 0 Lecture 1 Slide 2 Lecture 22 Slide 2 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 PHYSICS OF TECHNOLOGY Spring 2009 Assignment Sheet *Homework Handout

Temperature Introduction Section 0 Lecture 1 Slide 3 Lecture 22 Slide 3 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Physics of Technology PHYS 1800 Lecture 19 Temperature Temperature on an Atomic Scale

Temperature Introduction Section 0 Lecture 1 Slide 4 Lecture 22 Slide 4 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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/s 2 ) Force— what is required to change to motion of a body (MLT -2 or kg-m/s 2 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. (ML 2 T -2 or kg m 2 /s 2 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 mv 2 Potential Energy is the energy associated with an objects position. Gravitational potential energy PE gravity =mgh Spring potential energy PE apring = -kx Momentum— the potential of an object to induce motion in another object (MLT -1 or kg-m/s) Angular Momentum and Rotational Energy— the equivalent constants of motion for rotation (MT -1 or kg/s) and (MLT -2 or kg m/s 2 or N) Pressure— force divided by the area over which the force is applied (ML -1 T -1 or kg/m-s or N/m 2 or Pa)

Temperature Introduction Section 0 Lecture 1 Slide 5 Lecture 22 Slide 5 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Dennison’s Laws Thermal Poker (or How to Get a Hot Hand in Physics) 0 th Law: Full House beats Two Pairs 1 st Law: We’re playing the same game (but with a wild card) 2 nd Law: You can’t win in Vegas. 3 rd Law: In fact, you always loose. 0 th Law: Defines Temperature 1 st Law: Conservation of Energy (with heat) 2 nd Law: You can’t recover all heat losses (or defining entropy) 3 rd Law: You can never get to absolute 0.

Temperature Introduction Section 0 Lecture 1 Slide 6 Lecture 22 Slide 6 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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 Heat 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. Gas: No equilibrium position, no oscillations, atoms are free and move in perpetual high-speed “zig-zag” dance punctuated by collisions. gas liquid solid

Temperature Introduction Section 0 Lecture 1 Slide 7 Lecture 22 Slide 7 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring Heat k B is Boltzmann’s constant = J/K

Temperature Introduction Section 0 Lecture 1 Slide 8 Lecture 22 Slide 8 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Physics of Technology PHYS 1800 Lecture 19 Temperature Measuring Temperature (0 th Law of Thermodynamics)

Temperature Introduction Section 0 Lecture 1 Slide 9 Lecture 22 Slide 9 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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. –Corollary: Heat flows from hot to cold (DUH!!!)

Temperature Introduction Section 0 Lecture 1 Slide 10 Lecture 22 Slide 10 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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. Heat is a form of energy. (Here comes conservation of energy!!!) Temperature and Heat

Temperature Introduction Section 0 Lecture 1 Slide 11 Lecture 22 Slide 11 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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. They are both equal at -40 .

Temperature Introduction Section 0 Lecture 1 Slide 12 Lecture 22 Slide 12 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring KAbsolute zero º C 4.25Liquid He boils Liquid H boils Liquid N 2 boils Liquid O 2 boils CO 2 (dry ice) freezes Water freezes0 310Body temperature~ Gold melts Carbon arc Sun’s photosphere Iron Welding arc6020 Temperature Ranges

Temperature Introduction Section 0 Lecture 1 Slide 13 Lecture 22 Slide 13 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009

Temperature Introduction Section 0 Lecture 1 Slide 14 Lecture 22 Slide 14 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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?

Temperature Introduction Section 0 Lecture 1 Slide 15 Lecture 22 Slide 15 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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.

Temperature Introduction Section 0 Lecture 1 Slide 16 Lecture 22 Slide 16 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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,  C. Since negative pressure has no meaning, this suggests that the temperature can never get lower than  C, or 0 K (kelvin). Absolute zero

Temperature Introduction Section 0 Lecture 1 Slide 17 Lecture 22 Slide 17 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Can anything ever get colder than 0 K? No. Can absolute zero ever be reached? No. Absolute zero and the 3 rd Law of Thermodynamics

Temperature Introduction Section 0 Lecture 1 Slide 18 Lecture 22 Slide 18 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 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 318 room Review Ch 10