ELEC 225, Fall 2011
Prof. Rich Kozick

Homework 12


Date Assigned: Wednesday, November 16, 2011
Date Due: Wednesday, November 30, 2011
  1. Reading: In the Ulaby/Maharbiz text, please continue to study Chapter 7, Sections 7-1 through 7-9.

  2. Labs: We will do Lab 6 on Thursday, Nov. 17 and Lab 7 on Thursday, Dec. 1. Neither lab will require a formal lab report.

  3. Lectures: You may recall that we have one extra lecture session since we had the two mid-term exams on Fridays. Therefore the lecture on Wednesday, Nov. 30 is optional, and we will review Homework 12. No new material will be covered. The lecture schedule is as follows for the remainder of the semester:

  4. Final Exam: The final exam will be on Monday, Dec. 12 from 8:00 to 11:00 AM in a room to be determined room Breakiron 066. The exam will be cumulative, closed-book and closed-notes, and you can bring one sheet of 8.5" x 11" paper with notes written on both sides. You will also need a calculator. (Formulas for Y-Delta transformations will be provided, so you don't have to include them on your formula sheet.)

  5. Please solve the supplemental problem linked here and submit your solution in class on Wednesday, Nov. 30. (You should solve this problem before Nov. 23.)

  6. Please solve the following problems in Chapter 7 and submit solutions in class on Wednesday, Nov. 30. (You should solve all of these problems before Nov. 23.)
    Problems 7.23, 7.25, 7.27 (a, c, e), and 7.31.
    Optional problem (for homework extra credit): 7.34.

  7. Please solve the following problems in Chapter 7 (Thevenin equivalent circuits, nodal and mesh analysis), and submit solutions in class on Wednesday, Nov. 30. (You should solve some of these problems before Nov. 23.)
    Problems 7.35, 7.37, 7.47, 7.48, 7.51, 7.52, and 7.56.
    Note on Problem 7.37: The given circuit is improper at the specified frequency of 2500 rad/sec (but it is fine at every other frequency!). The voltage source has a short circuit across its terminals, which is a contradiction. We saw this after Y-to-Delta transformation in class on Nov. 28. Therefore the problem is not well-formulated. If you try to find the short-circuit current, you will get a contradiction.

    In order to get the values stated in the solution, find the open-circuit voltage using node-voltage analysis. Then find the equivalent impedance after deactivating the sources. If you try to use other methods (such as Y-to-Delta), you will see the contradiction.

    Don't let this problem confuse you. It is a poorly formulated question, and I did not realize the problem until we discussed it in class.

Thank you.