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Unformatted text preview: MatE 153: HW 1: Due Mon 9/12/11 • •
• Homework must be submitted on the due date by the start of class period. Homework will
be accepted during the class period but your grade will be reduced by 10%. After the end of
the class period, no homework will be accepted unless you have a verifiable, legitimate
Write your name very clearly on the upper right corner of the first page of your
You may work with up to 3 other students. List students you worked with. Be sure to
clearly separate their names from yours. You must submit your own set of solutions.
You will receive a 0 and be reported to the University if you submit any solution or partial
solution you did not actively participate in creating and fully understand (see the Greensheet
for more specific information).
You will see this material (though not the same or similar questions) on the midterm and
final. If you can’t do it now- come see me!! Reading Kasap: 2.1-2.3, 3.1-3.2 Total Points: 50 1. Electron drift mobility in indium has been measured to be 6 cm2 V-1 s-1. The room
temperature (27 °C) resistivity of In is 8.37 ×10-8 Ω m, and its atomic mass and density are
114.82 amu or g mol-1 and 7.31 g cm-3, respectively.
a. Based on the resistivity value, determine how many free electrons are donated by
each In atom in the crystal. How does this compare with the position of In in the
Periodic Table (Group IIIB)? (5 points)
b. If the mean speed of conduction electrons in In is 1.74 ×108 cm s-1, what is the
mean free path? (5 points)
2. A copper wire is connected to a 1 volt dc source. The dimensions of the wire are:
diameter = 0.05 cm and length = 1 m.
a. Find the current in the wire at a temperature of 20°C. (5 points)
b. Find the current in the wire at a temperature of –20°C. (5 points)
c. Explain the difference in the result for parts a.) and b.). (5 points)
d. Find the electron mobility at the two temperatures. (5 points)
e. The copper matrix is now alloyed with 10% (weight) gold. Find the current in the
wire at 20°C. HINT: The atomic percent of Au can be found by a result similar to
that in Example 2.10 and the Nordheim coefficient from Table 2.3. (5 points)
a. Calculate and compare the resistivity of a 25wt.% Ni – 75%wt.% Au alloy at
room temperature to that of a 25wt.% Mn –75wt.% Au alloy. What is the
percentage difference? (5 points) b. How do you explain the difference in the Nordheim coefficient between Ni/Au
and Mn/Au? (5 points)
4. In your own words, describe the photoelectric effect? What does the set-up look like
(anode, cathode, target material). Where do the emitted electrons come from? (5 points) ...
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This note was uploaded on 03/13/2012 for the course ISE 130 taught by Professor Patel,n during the Fall '08 term at San Jose State University .
- Fall '08