Materials science class homework

AI Thread Summary
The discussion revolves around a homework assignment in materials science that includes complex problems related to thermal and drift velocities of electrons, electrostatic forces in water molecules, and resistivity in composite materials. The user is struggling to identify the correct equations needed to solve these problems and mentions a lack of access to their textbook for reference. Suggestions are made to look up equations for thermal velocity, drift velocity, and electrostatic force, emphasizing the importance of understanding the underlying concepts. The user is encouraged to calculate the current density and use typical solid densities for the calculations. Overall, the thread highlights the challenges faced by students in applying theoretical knowledge to practical problems in materials science.
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I've got homework assignment for 6 hours later but I could not even start to solve the problems below. I've done lots of research but I could not understand which equation must be used for each question.1. Compare the thermal velocity with the drift velocity of electrons in a divalent metal wire carrying 7 A at 40 K. The wire has a diameter of 1mm. With the numbers that you’ve calculated, describe the motion of the electrons in a few sentences.

2. What is the electrostatic force on the oxygen atom in a water molecule? Please use an
oversimplified model with each atom having an apparent charge equal to its valence.
Remember that this is not a linear molecule.

3. A composite material is made of alternating thin lamellae of copper (resistivity 1.69 x 10^-6 ohm-cm) and a niobium-titanium alloy (resistivity 7 x 10^-5 ohm-cm) of equal thickness. (a) What is the resistivity of this composite measured parallel to the lamellae? If current is passed through the composite in this direction, what fraction of the current will be carried by the copper? How will the electric fields in the two phases compare? (b) What is the resistivity of this composite measured perpendicular to the lamellae? If current is passed through in this direction, what will be the ratio of the electric field in the alloy to that in the copper? (c) At a temperature of 4.2 K, the resistivity of the copper has decreased to 1 x 10^-8 ohm-cm, and the niobium-titanium alloy has become uperconducting. Answer questions (a) and (b) for this situation.
 

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Welcome to Physics Forums.

For #1 and #2, what equations have you been given for:
  • Thermal velocity?
  • Drift velocity?
  • Force between a pair of charges?
If you don't know, look in your textbook and class notes.
 
Redbelly98 said:
Welcome to Physics Forums.

For #1 and #2, what equations have you been given for:
  • Thermal velocity?
  • Drift velocity?
  • Force between a pair of charges?
If you don't know, look in your textbook and class notes.

Our textbook is not available at bookstore and also there is no electronic copy. There are equations in my notes but I can not use them because we could not get any example problem in the class. As you can see in the PDF file, there are no given equations. However, I found meanings and equations of the terms, you listed above, from internet but could not combine them for these specific questions.

Thanks.
 
If you have found an equation for thermal velocity, you should at least show what you have here. That one should be a pretty straightforward plug-in-the-numbers.

For drift velocity, you'll need to figure out the density of conducting electrons. Lacking specific information, I guess I would use a typical solid density in terms of atoms/cm3, and the fact that it is a divalent metal. The current and diameter can be used to calculate the current density.

Hope that helps get things going on #1 ... I am now logging off for the night however. Good luck.
 
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