{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Ek307Fall2007FinalExamSolution

Ek307Fall2007FinalExamSolution - pg1of8 EK307 — Electric...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 6
Background image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: pg1of8 EK307 — Electric Circuit Theory — Fall 2007 Final Exam 0 This exam consists of three parts: 1) Basic circuit theory questions; 2) RLC circuit problems, and 3) Lab questions. 0 You have two hours to complete this exam 0 Up to three sheets of notes plus calculator permitted. No other books or materials allowed. You may use your lab notebook for Part 3. 0 Put all answers in the boxes or on the graph axis provided. Credit will only be given for answers entered in the proper place. Part I — Ten Short answer questions ‘ _ Write the letter of the answer in the box provided. 1. Two 1.5-V D—cell batteries are used to power a small light bulb. The brightest light will be obtained by connecting the elements in which way? Answefi @Connect the cells in series with the bulb. b. Connect the cells in anti-series with the bulb. 0. Connect the cells in parallel with the bulb: (1. Connect the cells in anti-parallel with the bulb. ------ 6. Series or parallel makes no difference to bulb brightness as long as both cells are used. 2. An ohmmeter is connected to the circuit shown below at terminals A and B. The ohmmeter reads a. 25 £2 Answer. b. 50 Q A 50 Q 50 Q C c 75 Q d. 100 Q a e. 150 Q B 3. Which term describes the number of electrons flowing per unit time? a. Resistance (1. Power Answer: b. Capacitance e. Voltage @Current 4. How is an ammeter usually connected to a circuit under test? , In series with the circuit. Answer: . In parallel with the circuit. a c. In series and in parallel with the circuit. , d. In phase with the circuit. 6. With a coaxial clip-lead test cable. 5. A 4800-!) resistor is connected to a voltage source of value 120 cos cot V, where 0) = 2n x 60 Hz. What is the power dissipated in the resistor? . Answer. a. 3.0 W c. 4.2 W e b. 2.1 W d. 69.mW @15w p920f8 6. If three resistors are connected in parallel, their combined resistance is a. Equal to the average value of the individual resistors. Answer. @Always less than the value of any one resistor. b 0. Always larger than the value of any one resistor. d. Equal to the product of the three resistors. e. Equal to the sum of the three resistors. 7. What are the physical units of the product RC, where R= resistance and C= capacitance? a. Voltage b. Current Answer: @Time C d. Power e. Frequency 8. What is the resistance value seen between terminals A and B? Answer: a. 25 Q 1009 509 b d.ISOQ son 1009 9. What is the voltage vx? 100 Q 50 Q a. 1 V Answer: ®4V 12v 9 b c.6V d.3 V 6. 4.5V + VX ._ 10. A lO—pF capacitor is precharged to 10 V by a battery. At t = 0, the battery is disconnected, and a l-kQ resistor is connected across the capacitor’s terminal. After 10 ms, the capacitor has a. ...been discharged to a voltage of about 3.7 V .— b. ...been discharged to a voltage of about 6.3 V Answer: c. ...been discharged to 10 mV 6‘ GI). . .been discharged essentially to zero e. ...retained most of its lO-V charge. The resistor is too small to significantly discharge the capacitor in a few milliseconds. ’C‘RC: Hm. KMPP; I0 :1: 6 75-: I011»; =b %_’ = ’0 => 6 pg 3 of 8 Part II -— RLC Circuits (20 points each) 11. Consider the circuit shown below. a) Draw the Thévenin equivalent of everything connected to the diode. Specify the values of VT}, and Rm. 5.....................................................,..........‘..................................................................................................., VTh ~ J . \ Lg.> 2" +3“0 and 0-3;. 0,22. 2| l KVL Va : 011-02 = 0‘. [I + 7% + 7‘4“] - V V Kl l ., U'; - I: 5 d TzirR. 1+7... fill/2;. [1‘ 725: +7mEL 7‘! j , \ "‘ V41“ h ‘ £3 :: -7M°'l (Kit-22) WKIIZ-p) 2 ~ .: —- “4,0,2 :. _, a fll 9M 3 FTlAfluj U—Oc, ’U—Th j l 3 V [R WIZIWZLJ Wv‘l’k V090 =5 ‘7 =4 =1> 7h“- =° Mme”) "-R‘m; 23 pg4of8 12. Consider the circuit shown below. It has been energized for a long time prior to t = 0. VB; +5V =2: pF R1: 5kg VOUT W;5mv a) What IS the value of v1 fort<0‘7 V06 > S‘V W Hem, IS fie chm/71" «mm VI =” (‘M‘LH r VB +C’V ‘ 0t :0 W {I RI =b Vaw-I-zUL >(‘V c" Vac/1' Vim» i b) What IS the value of v1 for t > 0 after many timev constants of the circuit have elapsed? Hart 651"“: aura/7+ «21% VI- rV c. I— VI lg‘v varch ll) 0) Plot v1(t) for t > 0 on the axes provided. Label the voltage and time scales. la 20 30.20 n p950f8 13. The circuit shown below is designed to operate an alarm when the current through R2 exceeds 0.5 mA. a) Find the circuit time constant for t 3 0+ 1.. RTMC; zkn.x 24d: “ ”W U‘ .-. truly” ”:2” 5) Aim 0M reap/ire; 04-.“A. Thaw/7k 2,, =5 a; Q ) . o Ala/urn Wm +1411.“ 014 “JP-1’" Jag: UL. 435/11 __ V Sure“ Va: YT‘AG _. J WI“ NthZ—V R+TonJ ‘0 /J\ -T M 2v : §VD —. e °“/“° ‘] =1> So'vu‘w Tm 22V ' -T°'H£a .7: - . -. l _C / *5 _‘_ r .64 I —T ~. g m/‘tams = l~0.,_{ =o.é ‘13...“ -.-. o. : ~ I $12.1:C0-5' 00’0“) qams flufi 6) 0).? 22a ms (fir a ' J pg7of9 14. In problem, we explore the complex impedance Zn of the following circuit: LI: 100 mH L; 160 mH Zin :> R2 = 8 Q L4 g1 a) Express 2,, in terms of R1, R2, C1, C2, L, and 0). ¥.:. R,+-'— =72,~j>‘| ch.’ ~21 : 1'2L rwa; =mrixz, 2%.?— JtuL, 4 $411231 :JwL. «- @t-Jé‘w )LRu-Jx‘z) 2 % 12,1411. *J‘XL"¥1)J ‘ l l , ., l :‘jWLt 4 R‘ILL‘quxL FJ(X7/Rt‘xt’2¢) Kl WI. 4"; “LI/$9) b) If Zn = A +j B, find numbers for A and B if a) = 50 rad/sec. . 1 =_. 31.112. ; ~JWQWUMJ J9 JUL“ : JCfd)[0.l6H') =J‘ ? JwL. 2 Jide‘MH') ‘a‘r $0 3;: g ‘1‘? 2a: 8- fig 3.112,; (E flit)“ '77) “wt .___.._————-—-"—‘ : -— I6 EJ7— pg7of8 15. Consider the parallel RLC circuit shown below. The circuit is pre-energized with the switch closed. The switch is then opened at t = O. . Paulie! 2’- C- ' b) What are the roots of the characteristic equation? S: ‘3? i l 6’3)":- Vc.‘ with a=1 :-o.s‘_": car—«.1 2—0.3! A‘L‘I‘I o) Is the circuit under—damped or over-damped? under-damped [Z over-damped [:I d) What IS the initial condition for the voltage derivative de at 1‘ —~ 0? A-l- t‘ =o+ Vale) :ov Gila/+0 L “fiyjd M4 dc slw+olo+ => «71;»:4 W ~ *3 Bar C(o"=\/¢ -VV; ____g_bc(0 L. 5 E _ h-zsz-r-V LIA éfie’fi—J . -qk __ V = T”; “‘ch Nail ‘H'wf' cc: «LL—5,22 2 ’0‘1, wLJ'I—k 0’22 :0 ...
View Full Document

{[ snackBarMessage ]}