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Consider again the system of two large, identical Einstein solids treated in Problem 2.22.

(a) For the case N=1023, compute the entropy of this system (in terms of Boltzmann's constant), assuming that all of the microstates are allowed. (This is the system's entropy over long time scales.)

(b) Compute the entropy again, assuming that the system is in its most likely macro state. (This is the system's entropy over short time scales, except when there is a large and unlikely fluctuation away from the most likely macro state.)

(c) Is the issue of time scales really relevant to the entropy of this system?

(d) Suppose that, at a moment when the system is near its most likely macro state, you suddenly insert a partition between the solids so that they can no longer exchange energy. Now, even over long time scales, the entropy is given by your answer to part (b). Since this number is less than your answer to part (a), you have, in a sense, caused a violation of the second law of thermodynamics. Is this violation significant? Should we lose any sleep over it?

Short Answer

Expert verified

(a) The entropy of this method , assuming that each one of the microstates are allowed Stotal=3.826JK1

(b) The entropy again, assuming that the system in its presumably macro state Smp=3.826JK1

(c) The entropy is given by , but over while scales it's given by which is ever slightly larger than .Smp

(d) Placea superb excellent resistance between two surfaces, keeping them from transmitting energy. In effect, this shows that the model is stuck in its current condition.

Step by step solution

01

Einstein Spheres (a)

(a) Suppose two big, similar Einstein spheres, every with Nclocks and q=2Namount of energy. We had (from issue 2.22) for the state during which all business can make are able:

total24N8N

This complete agency's volatility is:

Stotal=klntotal

If we modify totalwith , we get:

Stotal=kln24N8N

ln(ab)=ln(a)+ln(b),lnab=ln(a)ln(b)andlnab=bln(a)

Stotal=k4Nln(2)12ln(8N)

k=1.381023JK1andN=1023:

Stotal=1.38102341023ln(2)12ln81023

Stotal=3.826JK1

02

Two solids (b)

(b) Its presumably situation, that the energy is spread evenly between the 2 solids, had a redundancy (from problem 2.22):

mp24N4N

The volatility of its most frequent state was even as follows:

Smp=klnmp

Assuming we swap mp, we get:

Smp=kln24N4N

Stotal=k[4Nln(2)ln(4N)]

k=1.381023JK1andN=1023

Smp=1.38102341023ln(2)ln41023

Smp=3.826JK1

Hence, whether object is viewed as either an unified location with all feasible microstates or as 2 independent systems for his or her most plausible shape, the energy is virtually defined solely more by 24Nvariable.

03

Entropy (c) and (d)

(c) The entity is liberal to pursue each one of the microstates included in Stotal, over longer timeframes, yet it's extremely likely to be in or near its most frequent state at any given time. Thus, we may claim that the entropy is supplied by Smp over small scales, while it's given by Stotal very long time scales, which has become so marginally bigger than Smp.

(d) Think about a situation within which we elect some extent t so when system is in its possibly efficient than one (i.e., the entropy is Smp) and so place a wonderful resistance between two surfaces, keeping them from transmitting energy. In effect, this shows that the model is stuck in its current condition.

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Most popular questions from this chapter

Suppose you flip1000 coins.
a What is the probability of getting exactly 500heads and 500tails? (Hint: First write down a formula for the total number of possible outcomes. Then, to determine the "multiplicity" of the 500-500"macrostate," use Stirling's approximation. If you have a fancy calculator that makes Stirling's approximation unnecessary, multiply all the numbers in this problem by 10, or 100, or1000, until Stirling's approximation becomes necessary.)
bWhat is the probability of getting exactly 600heads and400 tails?

Find an expression for the entropy of the two-dimensional ideal gas considered in Problem 2.26. Express your result in terms of U,AandN.

Using the same method as in the text, calculate the entropy of mixing for a system of two monatomic ideal gases, Aand B, whose relative proportion is arbitrary. Let Nbe the total number of molecules and letx be the fraction of these that are of speciesB . You should find

Smixing=Nk[xlnx+(1x)ln(1x)]

Check that this expression reduces to the one given in the text whenx=1/2 .

Use the Sackur-Tetrode equation to calculate the entropy of a mole of argon gas at room temperature and atmospheric pressure. Why is the entropy greater than that of a mole of helium under the same conditions?

Use a computer to produce a table and graph, like those in this section, for two interacting two-state paramagnets, each containing 100 elementary magnetic dipoles. Take a "unit" of energy to be the amount needed to flip a single dipole from the "up" state (parallel to the external field) to the "down" state (antiparallel). Suppose that the total number of units of energy, relative to the state with all dipoles pointing up, is80; this energy can be shared in any way between the two paramagnets. What is the most probable macrostate, and what is its probability? What is the least probable macrostate, and what is its probability?

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