Author Question: When calculating the Lorenz number L classically for electrical conductivity, you arrive at an ... (Read 61 times)

jon_i

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When calculating the Lorenz number L classically for electrical conductivity, you arrive at an answer that is proven wrong experimentally. Which of the following statements is NOT true about the quantum mechanical contribution to the value of L?
  a. Quantum mechanics provides that thermal conductivity K is proportional to electrical conductivity over Avogadro's number, /NA.
 
b. Only electrons moving near the Fermi speed will be a factor in the conductivity.
  c.Quantum mechanics predicts a larger Lorenz number than classically calculated.
  d. The quantum Lorenz number depends on a different configuration of the same physical constants that the classical number depends on.

Question 2

Which of the following is NOT a general selection rule for the filling of electron shells?
 
a. For a particular n, the subshells fill in the order s, p, d, f, ...
  b.Shielding affects the ordering of energy levels as described by n and l.
  c. The orbital and spin angular momentum in each shell and subshell are restricted by Hund's rules.
  d. Electrons usually completely fill a subshell before starting another shell.
  e. For the s shell there are 2 electrons, for the p shell 6, for the d shell 10, and for the f shell 16.



fur

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Answer to Question 1

This statement is not true. The thermal conductivity K is indeed directly proportional to the electrical conductivity, but it is also directly proportional to the temperature T, K
a.

Answer to Question 2

e.
This statement is not true. The f subshells each take 14 electrons. Each l value subshell can take 2(2l + 1) electrons.



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