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Unformatted text preview: University of California San Diego
Department of Eieotricai and Computer Engineering ECE 35 Final Exam
Winter 2008 Name (Last, First) Student ID Number 33‘ u lion; (3?) Signature This is a closed book exam, other than a single page of notes.
Cellphones, and electronics other than a nongraphing calculator, are absolutely forbidden. You must show your work to receive credit on any problem. Write clearly: work which is not legible
will not count towards your grade. All answers should be reduced to simplest form (decimal or fractions are OK). Answers MUST HAVE UNITS to be correct (i.e., 30, 2A, 4mV) Good exam policy:
(1) READ THROUGH THE ENTIRE EXAM BEFORE BEGINNING
(2) WORK ON THE SIMPLER PROBLEMS FIRST (3) TRY TO ANSWER ALL PROBLEMS Problem ‘1 (40 pts, 20 points each) 1A: Express the drive voltage at left as an equation and as a phasor +10V .ﬂ.
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(i) ReEtan ular:) = 2‘ + j Z “(L
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(ii) Polgr: V 2 = 2 E Z ““3 +5
(iii) Graplliixal (I be! axes and plot on scale at right) vd(t) = cos(1000t+45°) [V] K
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5!: Page as Problem 2 (40pts, 10 points each)
2A (15pts): Find the Thevenin equivalent to the drive circuit below, where i(t) = 500$(2t) 28 (15 pts): Find the load that maximizes power transfer into the load: show each element (resistor, capacitor. inductor)
20 (10 pts): Using this load. what is the reactive power dissipated in the entire circuit? #156357: damn. L=O.5H A) Can w.r“‘ Currl'.+ +0 ”LEI34 She/L; ; Page 3'6 Problem 3 (40 pts, 20 points each):
3A: Find the Thevenin equivalent, when R = 30, L = 0.1H, V1(t) = 4 oos(30t), and V2“) = 3 Sin(30t) v26) 5m Muston“; "it: in;
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c. 3A: Find the output voltage VAB when the second voltage source is changed to a DC 3V source.
Express your answer in the time domain. THO ‘F’bédCMCLIC—C —9 gJVfPDS;‘4ﬁ‘9W,
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Vkﬁ IF— 2_ \ ZI... 1—322 3 Problem 4 (40 pts)
4A & 4B (10 points each) What are the transfer functions H1(w) and H20») (Vow/Vin) for the two circuits below? 0° Pb) Ra .. A66 G5 Wl+17¢ div{al.zr" I 'Vcc
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H M a . ”out. “ RF (" I“) 5 4C: (5 pts) Which values deﬁned in the circuits limit the maximum transferred frequency, and how? i Qircu'J' 1‘: TransFer 'pIJcc'kou AirDP) Hear kerb (.1qu L1)? Fig;
Circ03+ 2; NO Fragacute? AwalOMCC. 4D: (5 pts) Which values deﬁned in the circuits limit the maximum and minimum transferred output voltage. and how? Circuit I‘ M» EJMII' (Unless Camemgnlr berm 9")
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4E: (5pts) 1f the output of the second circuit is connected to the input of the ﬁrst, what is the new transfer function? “‘ "' "’ 2F ‘ c
HUGJ): H1045 H‘(u)= .__.__. .Ji—a K5 iiﬂ'LJCEB
4F: (5 pts) Does this transfer function change of the order of the two circuits were reversed? Why?
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The switch in the circuit below is opened at time t=0 after being closed for a long time. T _ E“ to '
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Ft ri'jLi' "‘ RS : 18 Page 646 ...
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