ELEC 226, Spring 2009
Prof. Rich Kozick

Homework 3


Date Assigned: Wednesday, January 28, 2009
Date Due: Wednesday, February 4, 2009

  1. Reading: In the Nilsson/Riedel text, please continue to study Chapter 9, Sections 9.10, 9.11, 9.12, and review Sections 6.4 and 6.5 on mutual inductance. You may also find it useful to read Chapter 14 in the Bobrow text that you used in ELEC 120.
    Please study Chapter 10 for the week of February 2.

  2. Please solve the following problems in Chapter 9 and submit solutions in class on Feb. 4:
    Phasor diagrams: Problem 9.82. (In your phasor diagram, let Vs = Vm /_ 0o and consider Xc = 1/(omega C) to be a fixed number for a given frequency. Show the Vs and Vo phasors on your diagram as Rx varies from 0 to infinity.)
    Linear transformers: Problems 9.73, 9.74, and 9.75.
    Ideal transformers: Problems 9.77 and 9.80. Problem 9.80 is removed from Homework 3 and will be part of Homework 4.
    Hints sent by email on Feb. 1:

    • Problem 9.82: You do not have to include all of the phasors that are shown in the diagram in the back of the textbook. It is enough to show Vs and the way that Vo varies as Rx changes from 0 to infinity. It may help if you redraw the circuit as two voltage dividers in a "bridge".
    • Problem 9.73: The formula for the phasor of I_1 is given in the Linear Transformer notes in the link above. You just need to plug in the numbers for the given circuit, using M^2 = k^2 * L_1 * L_2.
    • Problem 9.74: Use the general formula for the Thevenin equivalent circuit that was given on the whiteboard in lab last Thursday. We will discuss the derivation of the Thevenin formulas in class this week, but you can solve this problem simply by plugging into the formulas.
    • Problem 9.75: Use the formula for Z_ab derived and given on the whiteboard in lab last Thursday.
    • Problem 9.77: This problem is very simple if you understand equation 9.91 in the text. We will talk about this in class on Monday, so if you wait until after class, you can solve this problem quickly.

  3. We will work with transformers in