ECE 201 Fall 2007 Exam 2 October 24 2007 Division 0101 Qi 7 30am Division 0201 Elliott 10 30 am Division 0301 Jiao 3 30 pm Division 0401 Peroulis 4 30 pm Instructions 1 DO NOT START UNTIL TOLD TO DO SO 2 Write your Name division professor and student ID PUID on your scantron sheet 3 This is a CLOSED BOOKS and CLOSED NOTES exam 4 There is only one correct answer to each question 5 Calculators are allowed but not necessary Please clear any formulas text or other information from your calculator memory prior to the exam 6 If extra paper is needed use back of test pages 7 Cheating will not be tolerated Cheating in this exam will result in an F in the course 8 If you cannot solve a question be sure to look at the other ones and come back to it if time permits 9 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 Outcomes i and iii were covered on Exam 1 You only need to satisfy the outcomes once during the course Course Outcome Exam Questions Total Points Possible i iii iv viii 5 7 11 1 4 7 11 4 36 36 45 9 Minimum Points required to satisfy course outcome 18 18 18 9 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 x t x x t o x e t t o L R 1 RC 1 For the following circuit find the short circuit current isc seen at terminals A B flowing out of terminal A and into terminal B 1 0 08A 2 0 01A 5 0 15A 6 0 1A 3 0 04A 2 4 0 03A 2 Find the Thevenin equivalent resistance seen at terminals A B for the following circuit 1 10 2 0 3 10 5 25 6 50 7 75 3 4 20 3 The Thevevin equivalent for the following circuit is 4 4 RL is a variable load resistor What is the maximum power the load resistor RL can absorb 1 5W 2 10W 3 15W 5 45W 6 60W 7 90W 5 4 30W 5 The voltage vL t appearing across an inductor of inductance L 4mH is shown in the plot below The current at t 0 is i 0 5A Which of the following plots represents the current i t 6 6 Suppose is t 2 cos 4t A Find ic t 1 120 sin 4t A 2 30 sin 4t A 3 30 cos 4t A 4 7 5 cos 4t A 5 30 sin 4t A 6 120 cos 4t A 7 7 In the circuit above the switch closes at t 0 sec VC1 0 9V and VC2 0 3V The current i t is shown below The initial current i 0 at t 0 and the time such 1 that i i 0 are e 1 i 0 0 6A 15 sec 2 i 0 0 2A 60 sec 3 i 0 0 4A 135 sec 4 i 0 0 4A 30 sec 5 i 0 0 6A 45 sec 6 i 0 0 2A 135 sec 7 i 0 0 6A 135 sec 8 8 Sketch iL t for t 0 9 9 In the following circuit determine the current i x 0 at t 0 1 150 mA 2 100 mA 3 50 mA 5 50 mA 6 100 mA 7 150 mA 10 4 0 10 Find vc t for t 0 0 t 4 1 2 3 4 5 6 7 1 e t 3 V 3 e t 3 V 3 e t 4 V 1 e t 3 V 1 e t 4 V 3 e t 4 V 2 e t 3 V t 4 1 t 4 3 2 2 e e V 1 t 4 3 1 1 e e V 1 t 4 4 2 2 e e V 1 t 4 4 1 2 e e V 1 t 4 4 2 1 e e V 1 t 4 4 2 1 e e V 1 t 4 3 1 1 e e V 11 11 A capacitor C with an initial charge Q is being discharged through a resistor R How much time does it take for the energy stored in the capacitor to be reduced by 50 1 RC 2 2 RC 3 2RC 5 RCAn2 6 2RCAn2 7 12 1 RCAn2 2 4 5RC 2
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