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ECE 2300 -- Exam #1
March 7, 2009
Keep this exam closed until you
are told to begin.
1. This exam is closed book, closed notes. You may use one 8.5” x 11”
crib sheet, or its equivalent.
2. Show all work on these pages. Show all work necessary to complete
the problem. A solution without the appropriate work shown will receive no
credit. A solution that is not given in a reasonable order will lose credit.
Clearly indicate your answer (for example by enclosing it in a box).
3. It is assumed that your work will begin on the same page as the
problem statement. If you choose to begin your work on another page, you
must indicate this on the page with the problem statement, with a clear
indication of where the work can be found. If your work continues on to
another page, indicate clearly where your work can be found. Failure
to indicate this clearly will result in a loss of credit.
4. Show all units in solutions, intermediate results, and figures. Units in
the exam will be included between square brackets.
5. Do not use red ink. Do not use red pencil.
6. You will have 90 minutes to work on this exam.
1. ________________/25
2. ________________/25
3. ________________/20
4. ________________/30
Total = 100
ECE 2300 Exam 1 – March 7, 2009 – Page 2
Room for extra work
ECE 2300 Exam 1 – March 7, 2009 – Page 3
{25 Points} Use the circuit below to solve this problem.
Find vQ.
Find vX.
Find the power delivered by the current source.
1.7[k]
-
2.2[k] vQ +
3.3[k]
12[V]
+
+
14[V]
-
-
+
vX
6.3[k]iQ
+
4.7[mA]
-
1.9[k]
+
1.
a)
b)
c)
6.8[k]
5.6[k]
iQ
7[V]
3.9[k]
ECE 2300 Exam 1 – March 7, 2009 – Page 4
Room for extra work
ECE 2300 Exam 1 – March 7, 2009 – Page 5
2. {25 Points} Use the circuit shown below to solve this problem. Show your
steps in some clear fashion. You are strongly encouraged to redraw the diagram as
needed to make your work more clear.
a) Find the equivalent resistance with respect to terminals F and J.
b) Find the equivalent resistance as seen by terminals A and L.
A
B
8.2[k]
C
7.5[k]
4.7[k]
D
6.8[k]
3.3[k]
F
G
5.6[k]
2.7[k]
E
1.7[k]
4.3[k]
2.2[k]
K
H
J
L
3.9[k]
ECE 2300 Exam 1 – March 7, 2009 – Page 6
Room for extra work
ECE 2300 Exam 1 – March 7, 2009 – Page 7
3. {20 Points} A measurement of the resistance of an unknown resistor RX is
attempted by a novice using a voltmeter and an ammeter, as shown in the circuit
below. The intention is to simultaneously measure the current through the resistor
with the ammeter, and the voltage across the resistor with the voltmeter. The
resistance will then be obtained from the ratio of these two readings. For this
problem, assume that the meter resistance for the ammeter is 300[], and its fullscale current is 2.5[mA]. For this problem, assume that the meter resistance for
the voltmeter is 10[k], and the full-scale voltage is 25[V].
a) If RX is 1.43[k], find the ratio of the voltmeter reading to the ammeter
reading in this circuit.
b) What voltmeter and ammeter characteristics would need to change to get a
measurement of resistance from this technique to be within 1% of the
correct answer, if RX is 1.43[k]?
RS = 1[k]
Ammeter
A
+
-
vS=
10[V]
V
Voltmeter
A
RX
B
ECE 2300 Exam 1 – March 7, 2009 – Page 8
Room for extra work
ECE 2300 Exam 1 – March 7, 2009 – Page 9
4. {30 Points} For the given circuit, use the Node-Voltage method to write a
complete set of independent equations that could be used to solve this circuit.
You only need to write one set of equations. Do not simplify the circuit. Do not
attempt to solve or simplify your equations. Define all variables.
11[V]
2iW
20[]
25[]
+
-
+
+
+
5[]iX
vX
10[V]
-
-
3vX
+
35[]
iX
24[]
-
29[]
+
26[]
16[V]
4[S]vW
13[A]
-
32[]
21[]
49[]
31[]
15[V]
33[]
+
22[]
14[A]
23[]
12[V]
iW
+
-
27[]
vW
+
ECE 2300 Exam 1 – March 7, 2009 – Page 10
Solutions:
1.
a)
b)
c)
{25 Points} Use the circuit below to solve this problem.
Find vQ.
Find vX.
Find the power delivered by the current source.
ECE 2300 Exam 1 – March 7, 2009 – Page 11
ECE 2300 Exam 1 – March 7, 2009 – Page 12
ECE 2300 Exam 1 – March 7, 2009 – Page 13
2. {25 Points} Use the circuit shown below to solve this problem. Show your steps in some
clear fashion. You are strongly encouraged to redraw the diagram as needed to make your work
more clear.
a) Find the equivalent resistance with respect to terminals F and J.
b) Find the equivalent resistance as seen by terminals A and L.
A
B
8.2[k]
C
7.5[k]
4.7[k]
D
6.8[k]
3.3[k]
F
G
5.6[k]
2.7[k]
E
1.7[k]
4.3[k]
2.2[k]
K
H
J
L
3.9[k]
ECE 2300 Exam 1 – March 7, 2009 – Page 14
ECE 2300 Exam 1 – March 7, 2009 – Page 15
ECE 2300 Exam 1 – March 7, 2009 – Page 16
3. {20 Points} A measurement of the resistance of an unknown resistor RX is attempted by a
novice using a voltmeter and an ammeter, as shown in the circuit below. The intention is to
simultaneously measure the current through the resistor with the ammeter, and the voltage across
the resistor with the voltmeter. The resistance will then be obtained from the ratio of these two
readings. For this problem, assume that the meter resistance for the ammeter is 300[], and its
full-scale current is 2.5[mA]. For this problem, assume that the meter resistance for the
voltmeter is 10[k], and the full-scale voltage is 25[V].
a) If RX is 1.43[k], find the ratio of the voltmeter reading to the ammeter reading in this
circuit.
b) What voltmeter and ammeter characteristics would need to change to get a measurement
of resistance from this technique to be within 1% of the correct answer, if RX is
1.43[k]?
RS = 1[k]
Ammeter
A
+
-
vS=
10[V]
V
Voltmeter
A
RX
B
ECE 2300 Exam 1 – March 7, 2009 – Page 17
ECE 2300 Exam 1 – March 7, 2009 – Page 18
ECE 2300 Exam 1 – March 7, 2009 – Page 19
4. {30 Points} For the given circuit, use the Node-Voltage method to write a complete set of
independent equations that could be used to solve this circuit. You only need to write one set of
equations. Do not simplify the circuit. Do not attempt to solve or simplify your equations.
Define all variables.
ECE 2300 Exam 1 – March 7, 2009 – Page 20