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PRACTICE TEST
GEORGIA INSTITUTE OF TECHNOLOGY
ECE 3710A: Circuits and Electronics
Fall 2011
Exam 2
Name: ___________________________________________________ The following may be used for this exam:
- One hand-written, two-sided 8.5”× 11” page with notes and formulas
- A calculator
Part A: Circuit Concepts
Instructions: The first section comprises ten (10) questions related to circuit concepts. Choose eight (8) questions and answer them completely. In the following table, place a checkmark (ü) corresponding to each question number you’ve chosen to answer. Only the eight questions specified below will be graded for correctness.
Part A: Circuit Concepts
Part B: Circuit Analysis
Instructions: Please answer all parts of the question completely, appropriately labeling diagrams and writing relevant equations. Remember to provide proper units and clearly indicate your final answers.
Exam Scoring
Part A /
Part B /
Final Grade
(avg. A + B)
PRACTICE TEST
Part A: Circuit Concepts
1. Determine the time required for this circuit to be considered in steady state. After this point what is the current in this circuit? What is the voltage across the capacitor? 2. I want to determine how the voltage at the inductor behaves in this circuit during transient time. After some “serious” derivations, I found that the voltage function with respect to time is parabolic. Do you think that I have made a mistake? Explain briefly. + - 200 V R = 100 W C = 500 pF t = 0 R 100 V t = 0 v ( t ) L + _ i ( t ) + vR ( t )^ _
PRACTICE TEST
6. One of my previous students said: “An impedance with value equal to 3 + j45 Ω can be represented with the following symbol: because the imaginary part is greater than the real part”. What is your evaluation about this statement? 7. During office hours, one student asks: “In the circuit below, I know that the resistors absorb some power, but I don’t know if the source is supplying all the power… Do you think the inductor can provide some power too?” If you were the instructor, how did you respond to this student? (Keep answers brief and technical)
IS
a
b
j 60 Ω
PRACTICE TEST
8. If ω = 1750 rad/s, determine the equivalent impedance ( Zin ) between terminals ( a , b ) and express your answer in polar form. 9. Do you agree with the following statement: “For any AC signal, the effective value is equal to the amplitude divided by √(2)”?
Zin
a
b
100 nF
100 mH
PRACTICE TEST
Part B: Circuit Analysis
Given the circuit below, please do the following:
1. Find v 1 (t) 2. What is the PF of the voltage source? 3. Check that the net power in this circuit is zero. PLEASE DRAW A CIRCLE OR BOX AROUND YOUR FINAL ANSWERS.
PRACTICE TEST
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PRACTICE TEST
Part B: Circuit Analysis
If vs ( t ) = 75cos(1000 ⋅ t) V in the circuit below:
1. Provide the Thévenin equivalent circuits at terminals (a, b). 2. Find the impedance value ( ZL ) that maximizes average power transferred to a load connected at the output terminals (a, b). PLEASE DRAW A CIRCLE OR BOX AROUND YOUR FINAL ANSWERS.
600 W
vs ( t )^40 W
a
b
6. 67 μF
0. 02 vo
150 mH
vo
_
PRACTICE TEST
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