Chapter 7: Q. 7.66 (page 323)
Short Answer
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Chapter 7: Q. 7.66 (page 323)
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Get started for freeEach 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?
(a) As usual when solving a problem on a computer, it's best to start by putting everything in terms of dimensionless variables. So define . Express the integral that defines , equation 7.122, in terms of these variables. You should obtain the equation
(b) According to Figure 7.33, the correct value of when is approximately . Plug in these values and check that the equation above is approximately satisfied.
(c) Now vary , holding fixed, to find the precise value of for . Repeat for values of ranging from up to , in increments of . Plot a graph of as a function of temperature.
In Section 6.5 I derived the useful relation between the Helmholtz free energy and the ordinary partition function. Use analogous argument to prove that , where is the grand partition function and is the grand free energy introduced in Problem 5.23.
For a system of particles at room temperature, how large must be before the Fermi-Dirac, Bose-Einstein, and Boltzmann distributions agree within ? Is this condition ever violated for the gases in our atmosphere? Explain.
At the center of the sun, the temperature is approximately and the concentration of electrons is approximately per cubic meter. Would it be (approximately) valid to treat these electrons as a "classical" ideal gas (using Boltzmann statistics), or as a degenerate Fermi gas (with ), or neither?
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