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Home , Georg Ohm, Heinrich Hertz, Inductance, James Prescott Joule, Oersted, Oliver Heaviside

Definition of

Ron Reifenberger Birck Nanotechnology Center Purdue University January 9, 2013

1 Lecture 1 A Brief History

• Prior to 18th Century, society supports advances in medicine (health) and astronomy (navigation; keeping) • Other realms of were viewed as a purely philosophic endeavor – not much in the way of experiments • mid 18th Century (1750’s); transition from rural to urban society – start of Industrial Revolution; “How is converted to in a ?” • 19th Century (1800-1850) scientists were encouraged to study engines and their efficiency; is a perpetual motion machine possible? • Two “Laws of ” emerge

2 TIMELINES Year and 1st Law Thermodynamics 2nd Law Thermodynamics Francis Hauksbee - first electrostatic 1706 generator Charles de Cisternay Dufay - electrified 1733 objects repel as well as attract Bernoulli uses idea of “atomic” 1738 motion to calculate Bishop Von Kleist & Cunaeus of Leyden - 1745 (first ) Ben Franklin - simple theory of 1746 electricity; two polarities of charge J. Black - discovers , latent ~1760 heat; inherently contradicts the calorique theory 1760-75 J. – invents steam engine (condenser) Chales ; law for 1785 Wm. Cleghorn – formulated coherent 1779 calorique theory Count Rumford (Benj. Thompson) 1790 questions while boring out canons in Boulton and Watt - commercial steam 1794 engines; first attempts to define w ork, power, horsepower, etc. Count Rumford – established connection 1798 between mechanical work and heat

1800 Alexandre Volta – first 3 Hans Christian – 1819 from current Andre Marie – first theory of the Herapath links heat w ith “atomic” 1820 magnetic field motion

1821 – primitive Carnot formulates 2nd Law; supports 1824 calorique theory 1827 Georg – Ohm’s Law

1830 – first Michael Faraday – electromagnetic 1831 induction 1833 Joesph – self

1834 Heinrich Lenz – Lenz’s Law

1837 – first telegraph James Prescott – heat produced by J.R. von Mayer – (heat + work) is 1842 conserved; initial formulation of 1st Law 1843-49 Joule’ s quantitative experiments Waterston first suggests that 1845 of gas “” is proportional to temperature Gustav Kirchoff – Kirchoff’s laws of 1846 electric circuits Helmholtz: , 1st 1847 Law of Thermodynamics 1850s – J.P. Joule – quantified heat & work in many ways – mechanical, 1850s electrical, etc.; Calorique theory of heat finally overturned 4 Clausius introduces concept of mean 1858 free path introduces idea of a 1859 distribution function Clausius introduces concept of 1865 – unified theory of thermodynamic ; Loschmidt electricity and magnetism estimates the size of an Boltzmann extends Maxwell’s mathematical derivation of 1868 distribution function w ith considerable physical insight Boltzmann’s transport equation proves that the MB distribution function is 1872 the ONLY one possible for a gas in thermal equilibrium on Electricity and Magnetism by James 1873 Clerk Maxwell Henry Row land – rotating static charge 1875 creates magnetic field 1876 –

1877 Boltzmann: S=kBln(w) 1879 – electric lamp Stefan-Boltzmann T4 law – connects 1884 thermodynamics w ith E&M William Stanley – electric 1886 and transmission of ac Heinrich – generation and Clausius, Maxwell, Boltzmann – kinetic 1887 detection of electromagnetic w aves theory of a gas (late 1800s) – reworks Maxwell’s 1887 theory – FOUR Maxwell equations Nikola – ; long- 1888 distance electrical transmission Gibbs publishes Elementary Principles 1902 in Statistical Mechanics 5 Why did it take ~100 years to sort all this out? A confusion between Temperature and Heat.

We all have a qualitative feel for what “heat”, “hot”, “cold”, etc. means, but how do we turn these qualitative feelings into quantitative concepts?

The answer to this question relies on an understanding how microscopic properties () translate into macroscopic measurable quantities.

The Science of Thermodynamics

Thermodynamics fundamentally was developed to understand the relationship between heat and work 6 While developing the Science of Thermodynamics, many Fundamental Conceptual problems arise

I. Is Heat Conserved? II. Is Cold the Opposite of Hot? III. How to Quantify Temperature? …….

Without a Science of Thermodynamics, many of these basic concepts are not well-defined

7 Example I: Water Wheel vs. Steam Engine

Steam in

Steam in Work is produced

Water in = Water out + Work Water is conserved. Heat in ?=? Heat out + Work Is Heat conserved? 8 Example II: Is “Hot” the opposite of “Cold”?

• Most people would claim that “Hot” and “Cold” are opposites.

• To make something hot, we add heat (measured in thermal units) because heat is energy.

• You can always provide “more heat” by adding more energy, so you can always make an object “hotter”.

• Therefore, by subtracting energy, you must have “less heat”; it follows that an object will get colder.

• But….., experiment shows you can only cool to -273.15oC, you can't get any colder.

• Since you can’t go any colder, you cannot continue to subtract more heat (or add “more cold”)?

• How then can “cold” be the opposite of “hot”?

• “Cold” is only a word used to describe the “absence of heat”. 9 Example III: Temperature – a way to quantify the “hotness” or “coldness” of an object

Which object is colder?

Styrofoam cup Piece of metal

You can’t even trust your sense of touch! 10 Thermodynamic Laws The Big Picture

Four 0th Law: Definition of thermal equilibrium 1st Law: U = Q - W – quantity of energy; in a closed system energy can be exchanged but it can not be created or destroyed 2nd Law: Definition of Entropy – quality of energy: when transforming “organized, useful” energy, some of it always deteriorates into “disorganized, non-useable” energy 3rd Law: The entropy of a system at zero absolute temperature is a well-defined constant because a system at zero temperature exists in its lowest energy () state. Its entropy is determined only by the degeneracy of the ground state. (Nernst 1906-1912).

11 To sort through these issues it is useful to list some of the attributes of temperature

• It’s a property usually associated with a system

• It’s a strange quantity – what are its origins?

• Not derived from ’s Laws of Motion!

• Distinguish between scientific (T=23.5oC) and colloquial (hot, cold, lukewarm, etc.) use

• Tightly coupled to local properties of well defined systems; e.g. “What’s the temperature of the earth?” is not a meaningful question

• Associated with equilibrium: constant T

• How do you measure temperature? 12 Highly accurate measures of temperature are hard to find!

• based on easily measured property of a common substance • easy to calibrate • the chosen to measure temperature should monotonically increase in value as T increases • physical property must be measurable over a wide range of • readily reproduced in other laboratories

13 Thermoscopes A simple constant- gas thermoscope

calibrated , m calibration mark moveable piston, area A

Force mg Pressure == gas PistonArea A units :[N / m2 ] = (Pa) 5 substance whose 1atm=1.01×10 Pa temperature you want to measure T=C1 P + C2

14 Implementation of a Constant Volume Gas Thermoscope

Patm Experiment showed this was a particularly reliable thermometer m ρ h mg P Patm A hA g Patm A P hg T atm 

T=C1 P + C2 1 atm = 760 mm of Hg = 760 Torr

Thermometers have scales printed one click on them; thermoscopes do not. 15 Can add Patm =Const. Defining Temperatures (or remove) using a Constant Volume Hg Gas Thermoscope

Pt Po and P100 are calibration measured at fixed mark P temperature points.

Volume V

What is tC (temperature of liquid bath)?

Pt -Po tC = x 100 (for scale) 16 P100 -Po Which gas is best?? Which Gas is Best? (measuring the boiling point of sulfur)

Pt

As Pt → 0, all gasses give the same answer. 17 Thermometers All Temperature Thermometers Rely on Fixed Points ( )

t = 9/5 t + 32 tC= 5/9 (tF-32) F C

Fixed Points

In the 1840’s there were ~18 different thermometer scales; 18 each country had their own! Negative Temperatures? Negative Temperatures?

This value does not depend on gas used

V1

V2

V3

Defines as –273.15oC

Note that temperature T= tC + 273.15 ( Scale) DIFFERENCES are the same19 The range of temperatures is enormous!

“Standard Temperature” = 273 K ~ 20 orders of magnitude!

20 0th Law of Thermodynamics

If objects A and B have the same temperature as object C, then objects A and B are also in thermal equilibrium with each other

21