Lect23

# Lect23 - PHYS 172: Modern Mechanics Lecture 23 Entropy and...

This preview shows pages 1–6. Sign up to view the full content.

Fall 2011 PHYS 172: Modern Mechanics Lecture 23 – Entropy and Temperature Read 12.3 - 12.5 1

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

View Full Document
First, an important reminder about multiplying probabilities : A deck of 52 cards has 4 aces. Starting from a randomly- shuffled deck, what is the probability that an ace is the first card dealt? P 1 = 4 52 = 0.0769 Once this happens, what is the probability that the second card is an ace? P 2 = 3 51 = 0.0588 So, what is the probability that the first two cards are aces? P two aces = P 1 ! P 2 = 4 52 ! 3 51 = (0.0769) ! (0.0588) = 0.00452 2
Last Time Einstein Model of Solids ( ) ( ) 1 ! ! 1 ! q N q N + ! " # = ! # microstates (N oscillators, q quanta) Fundamental assumption of statistical mechanics Over time, an isolated system in a given macrostate (total energy) is equally likely to be found in any of its microstates (microscopic distribution of energy). ! E = ! k m = ! " 3

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

View Full Document
These show the 15 different microstates where 4 quanta of energy are distributed among 3 oscillators (1 atom). The Fundamental Assumption of Statistical Mechanics A fundamental assumption of statistical mechanics is that in our state of macroscopic ignorance, each microstate (microscopic distribution of energy) corresponding to a given macrostate (total energy) is equally probable. 4
The fundamental assumption of statistical mechanics is that, over time, an isolated system in a given macrostate is equally likely to be found in any of its microstates. Most likely case:

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

View Full Document
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 PHYS 172 taught by Professor ? during the Fall '08 term at Purdue.

### Page1 / 21

Lect23 - PHYS 172: Modern Mechanics Lecture 23 Entropy and...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online