ECE 201 – Spring 2010

Exam #3

Wednesday, April 14, 2010

Division 0101: Prof. Capano (9:30am)

Division 0201: Prof. Tan (10:30 am)

Division 0301: Prof. Jung (7:30 am)

Division 0401: Prof. Capano (11:30am)

Instructions

  1. DO NOT START UNTIL TOLD TO DO SO.
  1. Write your Name, division, professor, and student ID# (PUID) on your scantron sheet.
  1. This is a CLOSED BOOKS and CLOSED NOTES exam.
  1. There is only one correct answer to each question.
  1. Calculators are allowed.
  1. If extra paper is needed, use back of test pages.
  1. Cheating will not be tolerated. Cheating in this exam will result in an F in the course.
  1. If you cannot solve a question, be sure to look at the other ones and come back to it if time permits.
  1. 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 iii, iv, v and ix. (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. If you fail to satisfy any of the course outcomes, don’t panic. There will be more opportunities for you to do so.

Course
Outcome / Exam
Questions / Total Points
Possible / Minimum Points required to satisfy course outcome
iii / 9 / 7 / 7
iv / 1-6 / 42 / 21
v / 11-14 / 28 / 14
ix / 7-10 / 28 / 14
  1. You will find formulas on the final page of this exam. You can tear the page out if you want to.

1. At t = 0 sec, the inductor current is iL(0+) = 5A and the capacitor voltage is vc(0+) = 0V. Find vc(t) for t ≥ 0s (in V).

(1) (2)

(3) (4)

(5) (6)

(7)

2.Find the resistance, R, which causes the roots of the characteristic equation s2 + bs + c = 0 to be identical for circuits (a) and (b) below.

(1) 1 (2) 2 (3) 3 (4) 4 

(5) 5 (6) 6 (7) 7 

3.In the circuit below, calculate diL(0+)/dt (in A/s), assuming iL(0) = 0 A and vc(0) = 50 V.

(1) 10,000(2) 20,000(3) 36(4) 40

(5) 5,000(6) 60(7) 8,000

4.The inductor current response for the circuit below is for t ≥ 0 sec. Find the initial condition vc(0) in V.

(1) 24(2) 12(3) 0(4) 12

(5) 24(6) 36(7) 48

5.In the circuit shown below, vc(0) = 1V and iL(0) = 0A. Which curve represents vc(t)? [Hint: You don’t need to find the exact equation for vc(t).]

(1)(2)

(3)(4)

(5)(6)

6.Find R (in ) in the circuit below so that the response vc(t) is critically damped for t ≥ 0 sec.

(1) 0.125(2) 0.25(3) 0.5(4) 1

(5) 2(6) 2.5(7) 5

7.In the ideal Op Amp circuit below, when vs1 = 10mV and vs2 = 5mV , vout = 15V. If
vs1 = 40mV and vs2 = +7mV, find vout (in V).

(1) 40(2) 26(3) 33(4) 0

(5) 15(6) 35(7) 47

8.In the circuit below, find vout.

(1) 1 V(2) 2V(3) 4V(4) 8V

(5) 1V(6) 2V(7) 4V

9.Determine the Thevenin equivalent resistance, RTH, and the short-circuit current, isc, for the ideal Op Amp circuit below.

(1) 2, 4A(2) 2, 2A (3) 6, 4A (4) 4, 6A

(5) 0, 0A (6) 6, 2A (7) 4, 2A

10.Find the output voltage vout(t) (in V) for t ≥ 0 sec for the ideal Op Amp circuit below, assuming that vc (0) = 2V.

(1) 12 e2t(2) 6 + 2 e2t(3) 6 e2t(4) 4 e2t

(5) 10 e2t(6) 6 – 2 e2t(7) 8 e2t

  1. Calculate the equivalent impedance, Zeq (in ), for the circuit below.

(1) (2) (3) (4)

(5) (6) (7)

12. The circuit shown below is in steady state. When vin(t) = 10cos(t), vout(t) = 5cos(t). Find (in rad/sec).

(1) 1(2) 10(3) 100(4) 1,000

(5) 10,000(6) 100,000(7) 1,000,000

13.The circuit shown below is in steady state. Find vL(t).

(1) (2)

(3) (4)

(5) (6)

(7)

14.The circuit below is in sinusoidal steady state. The phasor voltage and current at
 = 1 rad/sec are as shown graphically. Find the values of R and C.

(1) 0.10.17F(2) 0.1, 5.77F(3) 0.2, 0.08 F(4) 0.2, 2.89F

(5) 2.5, 0.43 F(6) 2.5, 4.33 F(7) 5 , 4.33 F

Potentially Useful Formulas

 = L/R

 = RC

, where

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