Questions and Answers
This page includes questions from ee205 students and the responses
from the instructor.
Q: What exactly is the course mailing list for? Is it to post our grades for the entire class to see? Is it for class announcements? I have never done this in a class before, so I would like to know what I would be getting myself into.
The mailing list is for class announcements from the instructor and for students in the class to communicate with each other. I will never post grades to the list. There is a risk that if it is popular, you will be getting a lot of e-mail from other students in the class. Since I am also on the list, I will make sure there aren't many postings that do not pertain to the course.
Q: What's up with example ___, I just can't seem to get the
same answers?
There are typo's in the book, so be ware and sorry about that.
Q: Is there a way to get the solutions posted on the web
so that we can print out copies of the solutions?
As noted in the syllabus, the solutions for all assigned problems are available in the
main office (front desk in Dreese Labs 205). As for posting them on the web,
I want to engage your mind as you look over the solutions.
Although it is inconvenient to come in, I feel that you will learn a lot
more by hand than you will by printing.
Q: So what's the deal with current through voltage sources?
While we're at it, voltage through current sources?
A: When in doubt, fall back on the i-v relationships. Current source: i
is dictated by the source, v is unknown (i.e., it can be anything, as
dictated by the circuit); voltage source: i is unknown, v is dictated by
the source; resistor: v=iR (note how there is no "R" for the ideal
sources). While on the subject, two sources in series will be additive.
E.g., for voltage sources using KVL, you will see the first voltage rise
(or drop) and then the next voltage rise (or drop). Also note that
sources with opposing orientations will (partially) cancel each other out.
Q: If I only know the current on one side of a two terminal device,
how do I find the current on the other?
A: Current is the flow of charge, since we are only working with two
terminal devices, what goes in must come out. So what does this mean for
serially connected devices? The same current flows through all of them.
But without further analysis, we don't know what happens with the voltage.
On the other hand, for devices connected in parallel, the same voltage
is present across each of them, but the individual currents flowing
through them are unknown. These two examples are analogs, switch
"voltage" with "current", then switch "parallel" with "serial" and you
have the same statement. KCL can be generalized to regions, not just
nodes. So the serial
example is simply KCL applied to a region that has two i/o lines and
multiple devices.