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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

For an Einstein solid with each of the following values of N and q , list all of the possible microstates, count them, and verify formula (N,q)=q+N1q=(q+N1)!q!(N1)!

(a) N=3,q=4

(b)N=3,q=5

(c) N=3,q=6

(d) N=4,q=2

(e) N=4,q=3

(f) N=1,q=anything

(g) N= anything, q=1

Fun with logarithms.
a Simplify the expressionealnb. (That is, write it in a way that doesn't involve logarithms.)
b Assuming that b<<a, prove that ln(a+b)(lna)+(b/a). (Hint: Factor out the afrom the argument of the logarithm, so that you can apply the approximation of part d of the previous problem.)

Suppose you flip 50fair coins.

(a) How many possible outcomes (microstates) are there?

(b) How many ways are there of getting exactly25heads and25tails?

(c) What is the probability of getting exactly 25heads and 25tails?

(d) What is the probability of getting exactly 30heads and 20tails?

(e) What is the probability of getting exactly 40heads and 10 tails?

(f) What is the probability of getting 50heads and no tails?

(g) Plot a graph of the probability of getting n heads, as a function of n.

Suppose you flip 20 fair coins.

(a) How many possible outcomes (microstates) are there?

(b) What is the probability of getting the sequence HTHHTTTHTHHHTHHHHTHT (in exactly that order)?

(c) What is the probability of getting 12 heads and 8 tails (in any order)?

Suppose you flip four fair coins.

(a) Make a list of all the possible outcomes, as in Table 2.1.

(b) Make a list of all the different "macrostates" and their probabilities.

(c) Compute the multiplicity of each macrostate using the combinatorial formula 2.6, and check that these results agree with what you got by bruteforce counting.

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