Version 09/27/05
EE 40 Homework Feedback from Readers in PDF Fall 05
HW 3
statistics: Mean 7.59 Std. Dev. 2.09
<>
1 a-c. were difficult to grade. If we saw that you had
a couple of correct currents and/or voltages you probably got credit.
>
a. 1pt.
b. 1pt.
c. 1pt.
d. Not graded
e. 0.5 each for Vth and
Rth
<>
2>
a. 1pt. All
or nothing, just had to get Vout
correct.
b. You got credit
if you had at least 3 voltage nodes
that were correct. Otherwise 0.6 off for each missing.
<>
3. >
a. 0.5
b. 1
c. 0.5
d. 1
<>
For problem 1, errors simply came from mixing up your
references! Pick ANY direction for your currents, if the current is
negative
that means it goes the other direction. When current travels
through a
resistor, there is a voltage drop across the resistor in the direction
of the
current. >
Many of you had incorrect
signs for 2a, 3b, and 3d. Remember,
the sign for voltage is based on how the element is referenced in the
circuit
diagram.
When asked to identify
voltages at ALL nodes, that means all
the wires between any two circuit elements. Not just nodes where
more
than one wire intersects.
To find the input or
output resistance, simply apply a test
voltage, and see what test current appears. Then the input or
output Resistance
is simply = Vtest/Itest.
Many people did not
calculate the thevenin voltage when told
to find the thevenin equivalent.
Many seemed confused by
3d. A source resistance is a
resistance connected in series to the source. A load resistance
is
connected across Vout, the output port. With those added into the
circuit, find Vout in terms of Vs, then divide by Vs to find Vout/Vs.
|