/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Q.7.14 For a system of particles at roo... [FREE SOLUTION] | 91影视

91影视

For a system of particles at room temperature, how large must -be before the Fermi-Dirac, Bose-Einstein, and Boltzmann distributions agree within 1%? Is this condition ever violated for the gases in our atmosphere? Explain.

Short Answer

Expert verified

As far as gases in the atmosphere are concerned, the condition was never violated.

Step by step solution

01

Given Information 

The Fermi-Dirac, Bose-Einstein and Boltzmann distribution lies within 1%of1.

02

Explanation

The quantum volume expression is:

vQ=h2mkT3

h=Planck's constant,

m=mass of gas molecule,

k=gas constant

T=temperature

vQ=quantum volume.

The pressure of gas molecule will be denoted by,

P0=kTZinme/TTv

Zint=partition function,

=chemical potential

P0=pressure at fixed temperature.

Substitute 2h2mkT3for vQin above expression,

Rearrange the terms,

-/kT=lnkTZintP02mkTh3..(1)

03

Explanation

The Bose-Einstein distribution's expression is:

nBE=1e(x)kT1

=energy at any state and

nBE=Bose-Einstein distribution.

The Fermi-Dirac distribution's expression is:

nFD=1e(k-)kT+1

nFDBose-Einstein distribution.

Equation (I) divided by equation (II) is:

nBEnFD=e(x)dT+1e(x)XT1=1+e(c)kT1e(c)kT1+2e()/kT

Here, ()/kT1so, the above approximation is valid.

04

Explanation

Calculation:

The value of e-(-)/kTShould be less than 1/200for the ratio to be within 1%of 1 ; it means the value (-)/kT>ln200=5.3.

The value of cannot be negative.

So, -/kTmust be greater than 5.3

Substitute localid="1651131552143" 1.3810-23J/K=k

300K=T

4.651026kg=m

localid="1651131671206" 6.631034J.s

50=Zint

105Pa=Pin equation (I).

/kT=ln1.381023J/K(300K)(50)105Pa24.651026kg1.381023J/K(300K)6.631034Js3=ln3108=ln3+8ln10=19.52

This indicates that the condition is valid since -mu/kTis greater than 5.3.

No violation of the condition occurred as far as atmospheric gases are concerned.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Consider a Bose gas confined in an isotropic harmonic trap, as in the previous problem. For this system, because the energy level structure is much simpler than that of a three-dimensional box, it is feasible to carry out the sum in equation 7.121 numerically, without approximating it as an integral.*

(a) Write equation 7.121 for this system as a sum over energy levels, taking degeneracy into account. Replace Tandwith the dimensionless variables t=kT/hfandc=/hf.

(b) Program a computer to calculate this sum for any given values of tandc. Show that, for N=2000, equation 7.121 is satisfied at t=15provided that c=-10.534. (Hint: You'll need to include approximately the first 200 energy levels in the sum.)

(c) For the same parameters as in part (b), plot the number of particles in each energy level as a function of energy.

(d) Now reduce tto 14 , and adjust the value of cuntil the sum again equals 2000. Plot the number of particles as a function of energy.

(e) Repeat part (d) for t=13,12,11,and10. You should find that the required value of cincreases toward zero but never quite reaches it. Discuss the results in some detail.

Although the integrals (7.53and 7.54) forNand Ucannot be

carried out analytically for all T, it's not difficult to evaluate them numerically

using a computer. This calculation has little relevance for electrons in metals (for

which the limit kT<<EFis always sufficient), but it is needed for liquid H3eand

for astrophysical systems like the electrons at the center of the sun.

(a) As a warm-up exercise, evaluate theNintegral (7.53) for the casekT=F

and =0, and check that your answer is consistent with the graph shown

above. (Hint: As always when solving a problem on a computer, it's best to

first put everything in terms of dimensionless variables. So let t=kTFrole="math" localid="1649996205331" ,c=F

, and x=kT. Rewrite everything in terms of these variables,

and then put it on the computer.)

(b) The next step is to vary holdingT fixed, until the integral works out to

the desired value,N. Do this for values of kTFranging from 0.1 up to 2,

and plot the results to reproduce Figure7.16. (It's probably not a good idea

to try to use numerical methods when kTF is much smaller than 0.1, since

you can start getting overflow errors from exponentiating large numbers.

But this is the region where we've already solved the problem analytically.)

(c) Plug your calculated values of碌 into the energy integral (7.54), and evaluate

that integral numerically to obtain the energy as a function of temperature

forkTup to 2F Plot the results, and evaluate the slope to obtain the

heat capacity. Check that the heat capacity has the expected behavior at

both low and high temperatures.

The speed of sound in copper is 3560m/s. Use this value to calculate its theoretical Debye temperature. Then determine the experimental Debye temperature from Figure 7.28, and compare.

Each atom in a chunk of copper contributes one conduction electron. Look up the density and atomic mass of copper, and calculate the Fermi energy, the Fermi temperature, the degeneracy pressure, and the contribution of the degeneracy pressure to the bulk modulus. Is room temperature sufficiently low to treat this system as a degenerate electron gas?

Consider a system of five particles, inside a container where the allowed energy levels are nondegenerate and evenly spaced. For instance, the particles could be trapped in a one-dimensional harmonic oscillator potential. In this problem you will consider the allowed states for this system, depending on whether the particles are identical fermions, identical bosons, or distinguishable particles.

(a) Describe the ground state of this system, for each of these three cases.

(b) Suppose that the system has one unit of energy (above the ground state). Describe the allowed states of the system, for each of the three cases. How many possible system states are there in each case?

(c) Repeat part (b) for two units of energy and for three units of energy.

(d) Suppose that the temperature of this system is low, so that the total energy is low (though not necessarily zero). In what way will the behavior of the bosonic system differ from that of the system of distinguishable particles? Discuss.

See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.