Exam_1_Soln

Exam_1_Soln - Last Name I'1 L3 First r‘ A a Section...

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Unformatted text preview: Last Name: ' I»? '1» L3 First:_# r‘ A) a Section: Masnari 001 / Escuti 002 (Circle one) ECE 200 — Fall 2007 — Exam 1 Instructors: M.J. Escuti & N.A. Masnari #1 #2 #3 #4 #5 12 16 l 10 14 l 16 Instructions: 1) Closed book / Closed Notes. 2) No scrap paper. 3) Calculators are NOT allowed. 4) Show your work step by step so we can give partial credit when possible. 5) Be neat — we should be able to read/follow what you wrote. i’roblem 1 (12 pts) Fill in the blanks below with the most accurate word to complete the statements. (a) In an electronic circuit, current is a measure of the number of charges per unit time flowing Z infigqu an element, and is measured in units of g mp: Q COwl/J‘ac) (b) L1 2( fig 9 is a measure of energy it takes to move a unit charge across an electronic element, also called the potential c1 ,‘ Egg (3 , and is measured in units of Volts. (c) Electrons flow in the circle one) direction as a positive current. (d) A tCSl'STdr is a passive and dissipating electrical element with 2 W0 terminals and a linear relationship between V0 I g and Qutgggf: _. (e) The C apaqg Ege is the defining parameter of a capacitor that relates the amount of stored g to the voltage. Note that while the C M 5:31: through a capacitor can change instantaneously, the V0 1! tag: across a capacitor cannot. Last Name: First: a Section: Masnari 001 / Escuti 002 (Circle one) Problem 2 (16 points) [2 pts each] Sketch the I-V curves for the following electrical elements, labeling any important points. Make sure to graph the entire range of possible values. (Note: the intersection of the axes corresponds to zero current and voltage) (a) Ideal Wire (b) Ideal Open Circuit 1 I —-—> (c) [4 pts] A 1 m length of metal wire has a resistance of 10 Q. It has a square cross—section with ‘L— 1 mm on a side, What 's the resistivit of the metal in units of Q-cm? R E [37:— L = / M) I I "‘w‘ _ 3§Z_Cm .'_ L: Mo a", I4= IMZJC’W 1: 0.0106412 ) 0mm / g _, —; (lodkwfi = £62,3—— : /0 _ I? _ /afl [960]) a (3 /00 (d) [4 pts] A l nF parallel—plate capacitor with an area of 10“2 m2 is filled with a material that has a permittivity of 10 x 10’14 F/m. What is the separaticin distance between the two plates? ~ A - «A (/ox/o""F/ ( ~2 9 —4 C- E’ -— : £2.— : . m ’0 m _- - c! a! C (])/0“4’F c1 -' (e) [2 pts] Label the anode and cathode of the diode below: cafHAooig l‘ 4no<i¢ (f) [2 pts] Describe one way that an ideal diode is difl?erent from an actual or “real” diode: I‘” be: on exgommaxing Mame, ivx C(M’i‘tmj~ MK" #49! 7"“1 “LIN/70+ mar/nan Gurraujt (jg an ileéd Jificif- Q0) ii‘ is OFF/ an Mj‘ual attack. [443 at SMaU W511 Sk‘r‘urfiw “fl/J. (C31? The, (Lacie 7S next/MQJ Mar-eel 7?) it lfi'jt'emvuylx WH‘fje/ 57" wi/l "Iowa/c ol/tu'wk m4 ref? Jed‘rmff. Last Name:_ First:__ a Section: Masnari 001 / Escuti 002 (Circle one) Problem 3 (10 pts) The circuit below—left with eight elements can be reduced to an equivalent circuit (below—right) using the principles of series, parallel, shorted, and open circuit elements. Find the equivalent resistance Reg and capacitance Ceq. Assume that R = 3 kg and C = 6 uF. Original Circuit: Elm/f Last Name: _ First:_ a Section: Masnari 001 / Escuti 002 (Circle one) Problem 4 (14 pts) Consider the circuit below. (a) Label the voltage polarities on all resistors that correspond with the given current directions (on the circuit diagram). ' (b) Apply KirchofPs Voltage and Current Laws to obtain three (3) independent equations (two KVL and one KCL), which can be solved to determine the currents 11, 12 and 13‘ Note that your equations will include the voltages V1, V2, V3 and the resistors, R1, R2, R3, R4 in addition to the three currents. Do NOT solve the equations. LaSt Name:_________ First____ a Section: Masnari 001 / Escuti 002 (Circle one) Problem 5 (16 pts) The diode in the circuit below has a turn—on voltage of V7 : 1 V, VI : 5 V , and V2 : 2 V, A (a) 4550mm JIDJQ is flFF, 10 k9 A [Olin + + +- ~.. Vr5V-” I’ __ \4— Z l + _ 8 m kJL ~71: + 5V~/oZ—2V—/ozfzo T (UNI—24110 ‘ h I h ' '- " a M (a) Determme 1f the diode IS ON or OFF. (Show your work!) - f I fig/— _ c9 / 25 H- W : s‘V- rm 4v +VD20 VD 2—3’V—lL /().7: :-3V+ Uo)(0.rz<l\/ : ~3+lx715 . / :> 0““ 4W at 01224; {Ff ,3, Correct, (b) Calculate the voltage at node A relative to ground. \grwr +S‘\/:(~q)[0,/25‘>V+S’V : f— 0.5 Last Name: First: a Section: Masnari 001 / Escuti 002 (Circle one) Problem 6 (16 pts) In the circuit below, the capacitor is initially uncharged. The various elements in the circuit have valuesofVS:5V,RI:5kQ,RZ~—-10kQ,andC=10,uF. i=0 lag) 18/ ,mflem we. see —’ 7% Jr a» 2‘ 40 o a" r .4 ) is“) R _, 2 (a) Solve for the following, just after the switch is closed: vc<0+>= vczfl : a V iC(0+)= 0. 5 m4 im(0+)=/€Rl(0') : /,0 MA ~ ‘ *- AS [0 9:»,260'4') imigo) l Mew, kW. RH» Mop afl‘ taa“ 1‘s: - ~ :; 0 R. R2 ‘ (b) Solve for the following, after along time: 4 A, (flfl 3 R 1 e (if) : 4i Alexa 1.) C I / Llel ‘ ’0 ic(°°)=0 (C WWW/“WW \ we): ' W- asm é i5<0+>= /.§m/4 Ac, :fi, , . VC(OO): V 1" :4”. S . \ \ A. (9* = 1" +A im<oo)=/.ow4 sé ) 42.60) <— "" ‘ ‘k :3 e W iS(oo)= 1,0 ASCO ) I 3”" Last Name: First: a Section: Masnari 001 / Escuti 002 (Circle one) Problem 7 (16 pts) The circuit at right has been connected as shown for a very long time before the switch is closed at t z 0. E “(V- Ckf‘: ’9”. t>0 flue 43$) (a) Sketch the voltage vC2(t) across and the current ic72 (t) through C2 as a function of time. Make sure that the initial and final values of vC2(t) and icz (I) are specifically shown. voltage v90) ' currenti (t) i «— v (0 1“l = lé C2 (b) Find an expression for the time at which the voltage vC2(t) reaches half of its maximum value. Express your answer in terms of the appropriate circuit element values (ie. potentially including C2, C1, R2. R2. R1. or Vol lube ;,_{.!__’-\(iw “fl/U5. m :K \1"1“»\’\&’ ‘5";‘v‘f'fi L“? “a m ‘ ...,. v‘ ., ,_ ~" , ‘ ,; . it ._.fi.a r -‘ "" .3 \yxs‘suiflt‘a: , t if: Ve.\‘"‘itk£‘t€£€, "2 ‘v “3“” "M" e" {5"} M 0“ If “ , ""VRC; ° Neil}, C4,“ :1; cfwalniéavmu" ,z', “who; 5 diving 313;" U m. ‘° Rich: ii" CHM:3&35‘53‘i" Jig?" .. v _ " i i) . ' t A, x “We” "1?! in {Rug (1th “A A mt: v l b t “3!”: .3. \ L.:V\;J\ \m : Mtge” = «We r (+3 \9.m'ii{3i ."VMJF __ “my: I :3. ‘1 . h. "--'~"“-'f:—‘-”"" :2 A ,r ._ ,L‘Zb é “:1 Lyvfila S Last Name: First: a Section: Masnari 001 / Escuti 002 (Circle one) Extra Credit Problem (5 pts) You are given a “black—box” containing a simple (but unknown) circuit potentially containing resistors, capacitors, diodes, switches, and voltage sources. When a DC voltage is applied across the two terminals of the black-box as indicated, the current I varies as a function of the voltage V as shown. Propose one possible circuit that could be in the black box (with element values). I—V Characteristic Betweenfiodes A—B current (mA) I A o—g : \/ : Black-Box l 3 ,‘n : .(u niknovvn } l Clrcwt lnSIde) I 2 B o———: i i i 1 voltage (V) L _ _ _ _ _ _ _ _ _ _ _ _ ___l —————> O 1 2 3 4 N07? fixati— (Ll/ulcwa cidem‘f hey/vi ugh/A? (M4de 71m. affixed [/9 /?‘a7€. YMOC‘gI /K/) .6044 flier/1 “We 0%rrm—i'1hcreay65 l1h349’/// wffli Merged“ ,\,\ \/l\n / Wis {\mrfiilu flue black Lax cam Wham a aha/(87” a; s/Vw’olg as a 4:941 (Va/:N/j m tie/rived; wiffi 5‘ MEAN/7w Rt/Ar—ZziL/2/I/Cflv AI 3M4 i, ; / +5"‘T { HI i”! V ‘ / m 1 lg”) H l B\ _ .__.—— i ...
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Exam_1_Soln - Last Name I'1 L3 First r‘ A a Section...

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