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ECE 201 – Fall 2011
Exam
8 - 9 pm, October 24, 2011
Division 0 1 : Qi ( 11 :30am)
Division 0 2 : Clark ( 7 :30 am)
Division 0 3 : Narimanov ( 1 :30 pm)
Instructions
- DO NOT START UNTIL TOLD TO DO SO.
- Write your Name, division, professor, and student ID# on your scantron sheet. We may check PUIDs.
- This is a CLOSED BOOKS and CLOSED NOTES exam.
- Calculators are allowed (but not necessary). If extra paper is needed, use back of test pages.
- Cheating will not be tolerated. Cheating in this exam will result in an F in the course.
Using any cell phone or networked devices is regarded as cheating.
Continuing writing after exam time is up is regarded as cheating.
- Please do not turn in scantron sheet 5 minutes before the exam time is up. We might take10 points off
your score if you do so.
- If you cannot solve a question, be sure to look at the other ones and come back to it if time permits.
- As described in the course syllabus, we must certify that every student who receives a passing grade
in this course has satisfied each of the course outcomes. On this exam, you have the opportunity to
satisfy outcomes i, iii, iv, and viii. (See the course syllabus for a complete description of each
outcome.) On the chart below, we list the criteria we use for determining whether you have satisfied
these course outcomes. Outcome i is a repeat. We use this outcome result only if you did not satisfy
it previously.
Course
Outcome
Exam
Questions
Total
Questions
Minimum # of correct responses
required to satisfy course outcome
i 1,2,3,4,5,6,9 7 1
iii 1,2,3,4,11 5 1
iv 7,8,9,10,11,12,13 7 1
viii 1,2,3,4, 4 1
If you fail to satisfy any of the course outcomes, don’t panic. There will be more opportunities for
you to do so.
Potentially useful formulas are:
o
t t /
o
x(t) x( ) x(t ) x( ) e
= L/R = RC
o
LC
1. In the circuit below, determine the short-circuit current, i SC
(1) 1 A (2) 2 A (3) 3 A (4) 4 A
(5) 5 A (6) 6 A (7) 7A (8) 8 A
(9) 0A (10) None of the above.
2. In the circuit below, determine the open-circuit voltage V OC
(1) 1 V (2) – 2 V (3) 3 V (4) – 4 V
(5) 7 V (6) 10 V (7) 12 V (8) – 9 V
(9) 0 V (10) None of the above.
5. Compute the equivalent inductance L eq
of the circuit shown below:
(1) 1 H (2) 2 H (3) 3 H (4) 4 H
(5) None of the above.
6. Compute the equivalent capacitance between nodes A and B of the circuit shown below:
(1) 1F (2) 2F (3) 3F (4) 4F
(5) None of the above.
A
B
7. The current through an inductor, L = 1 mH, is shown in the plot for 0 < t < 6 ms. Determine
the voltage V L
at t = 5 ms.
(1) 1 mV (2) 2 mV (3) – 5 mV (4) 10 mV (5) None of the above
8. The capacitor voltage at t = 0 in the circuit shown is V c
(0) = 100 V. Determine the power
absorbed by the resistor (in W), as a function of time for t > 0.
(1) 5 e
(2) 5 e
(3) e
(4) 0.4 e
(5) None of the above.
11. In a first-order RL circuit, the responses of the inductor current to the initial inductor current,
a voltage source, and a current source are,
Initial inductor current:
2 t
e
Voltage source:
2
t
e
Current source:
2
t
e
If the voltage source excitation is increased by a factor of three, the current source excitation is
decreased by 50%, and everything else remains the same; find the total response of the inductor
current.
2
t
e
A (2)
2
t
e
A (3)
2
t
e
A (4)
2
t
e
A
2
t
e
A (6)
2
t
e
A (7)
2
t
e
A (8)
2
t
e
A
2
t
e
A (10) None of the above.
12. The switch changes from position “A” to “B” at time t = 0. Assume the capacitor voltage
C 0 0
v (t) Acos t Bsin t for t > 0, the angular frequency,
, is:
3
rad/s (2)
3
rad/s (3)
3
rad/s
3
rad/s (5) 1×
3
rad/s (6) 2×
3
rad/s
(7) 4 ×
3
rad/s (8) 8 ×
3
rad/s (9) 16×
3
rad/s
(10) none of the above.
A
B
0.5 V
2 H
v
C
(t) 8 F
13. Using the information provided in the previous question, determine the total energy stored in
the two elements (inductor and capacitor) at t = 10 × 10
seconds for the circuit shown in the
previous question.
(1) J (2) 2 J (3) 5 J (4) 0.25 J (5) 0. 5 J
(6) 1 J (7) 1.5J (8) 2.5 J (9) 5 J (10) none of the above.
1. In the circuit below, determine the short-circuit current, i SC
(1) 1 A (2) 2 A (3) 3 A (4) 4 A
(5) 5 A (6) 6 A (7) 7A (8) 8 A
(9) 0A (10) None of the above.
2. In the circuit below, determine the open-circuit voltage V OC
(1) 1 V (2) – 2 V (3) 3 V (4) – 4 V
(5) 7 V (6) 10 V (7) 12 V (8) – 9 V
(9) 0 V (10) None of the above.
3. In the circuit below, determine the Thevenin equivalent resistance, R Th
, and open-circuit
voltage V OC
(1) 14 – 8 V (2) 20V (3) 410V (4) – 6 –8V
(5) 210V (6) – 6 4 V (7) 122V (8) – 3 –4V
(9) – 8 –6V (10) None of the above.
4. In the circuit below, determine the maximum power that is transferable to an optimally chosen
load resistor, R load
(1) 12W (2) 27W (3) 36 W (4) 48V
(5) 16W (6) 4W (7) 72W (8) 144W
(9) 0W (10) None of the above.
7. The current through an inductor, L = 1 mH, is shown in the plot for 0 < t < 6 ms. Determine
the voltage V L
at t = 5 ms.
(1) 1 mV (2) 2 mV (3) – 5 mV (4) 10 mV (5) None of the above
8. The capacitor voltage at t = 0 in the circuit shown is V c
(0) = 100 V. Determine the power
absorbed by the resistor (in W), as a function of time for t > 0.
(1) 5 e
(2) 5 e
(3) e
(4) 0.4 e
(5) None of the above.
9. In the circuit below the switch has been at position “A” for a long time. At t = 1 second it
changes from position “A” to position “B”. Find the capacitor voltage, v C
, for t ≥ 1 s.
(1) 30e
- (t-1)/
V (2) 60e
- (t-1)/
V (3) 100e
- (t-1)/
V (4) – 60+100e
- (t-1)/
V
(5) 30+70e
V (6) 30e
- 2(t-1)
V ( 7 ) 60e
- 2(t-1)
V ( 8 ) 100e
- 2(t-1)
V
( 9 ) 40+30e
- 2(t-1)
V (10) None of the above
10. In a first-order RL circuit excited by a current source, the inductor current (in A) is
represented as
4
3
t
L
i t e
Find the time (in seconds) required for the i L
( t ) to change from 10 A to 8 A.
(1) 5 ln2 (2) 5 ln3 (3) 5 ln4 (4) 5 ln5 (5) 4 ln
(6) 4 ln3 (7) 4 ln4 (8) 3 ln2 (9) 3 ln3 (10) 3 ln
100 V
v
C
6
4
3
0.25 F
t = 1 s
A
B
13. Using the information provided in the previous question, determine the total energy stored in
the two elements (inductor and capacitor) at t = 10 × 10
seconds for the circuit shown in the
previous question.
(1) J (2) 2 J (3) 5 J (4) 0.25 J (5) 0. 5 J
(6) 1 J (7) 1.5J (8) 2.5 J (9) 5 J (10) none of the above.
