Lesson 7



Name:ETP Section:t3 Start Time:22:46:46 Instructor:pattersonet Course:421




1. In your own words, describe what a "partition function" is. Is it likely that it has lots of terms which are equal, or very few terms which are equal? Briefly explain.

Enter your answer here:



2. Think about a system of N magnetic atoms which are placed in an external magnetic field B and which can each be in two possible states. Let the "+" state be the state for which B and the magnetic moment of an atom, m, are aligned (parallel), and let the "-" state be the state for which B and m are anti-aligned (anti-parallel).

Write expressions for the magnetic energy E+ and E- of an atom in each of the two states, and write also write expressions for the probability of finding an atom in each of these states. (These expressions should be very simple.)

What do your answers tell you about the likelihood of finding an atom in each of these two states? Does this make physical sense to you?

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3. The probability P(Es) = (1/Z)*exp(-Es/kT)

Check the correct answer:
a) gives the probability of finding the system with energy Es
b) gives the probability of finding the system in a particular state s with energy Es
c) is normalized because Z is summed over all energies Es
d) is sharply peaked about the most probable energy E

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