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last ﬁrst 123 Section B exam Write your name and student number on all ﬁve pages. Problem VI asks for a written answer—be concise yet complete, and write legibly.
T 0 receive credit, you must brieﬂy explain the major steps you take, “naked”
answers receive none. Your job is to convince the grader that you know what you
are doing. In answering multiplechoice questions, choose the best response. Problem I Faraday’s Law [15 points] The resistance of the square loop at the right is 0.01 Q, and a 0.150 A induced current is ﬂowing ccw as shown.
8.0 cm 1. (2 pts) The externally applied magnetic ﬁeld strength is A. adequate B. decreasing ©increasing D. constant 2. (3 pts) What is the magnitude of the induced emf (in millivolts)?
A. 0.150 B. 15.0 @150 D. 0.50 E. 3.68 3. (5 pts) What is the direction of the induced Bﬁeld?
A. cw B. ccw C. can’t be determined D. into the page @ut of the page 4. (5 pts) At what rate (in T/s) is B changing?
A. 0.0234 B. 2.34 C. 1.60 D. 0.50 @0234 Problem 11 Motional EMF [15 points] A 30.0cm long conducting rod moves in a plane that is
perpendicular to a magnetic ﬁeld of 0.050 T. The constant speed v of
the rod is perpendicular to its length. 5. (5 pts) When charge distribution is not changing, the magnitude
of the electric ﬁeld in the rod is given by A. E=0.00 9E=vB C. E=vIB D. E = Q/(41teol ) E. none of these 6. (5 pts) If the potential difference between the ends measures 6.00 V, then v (in m/s) is
400 B. 40 C. 160 D. 533 E. 3.68 7. (5 pts) What force (in N) is required to keep the rod moving at speed v? .000 B. 0.98 C. 1.60 D. 0.50 E. 3.68 Physics 1238, Winter 2009, Version a Exam 1, page 1 Name Student ID Number
last ﬁrst Problem 111. Response of an RL circuit [5 pts]
8. (5 pts) The open switch in the RL L v
R circuit shown on the right is closed at WWW time t = 0. Which curve best illustrates S i the variation of the magnitude of 1 potential difference across the inductor as a function of time? ”'1 » Battery
A. B. C. D. ® Problem VI. Another RL Circuit?! [10 points] 100 For this second RL circuit shown on the right, the switch is initially open. +
30 V .2 20 0 IO mH 9. (5 pts) What is the current I (in A) through theIO £2
resistor immediately after the switch is closed? A. 2.00 B. 050 @ 1.00 D. 2.50 E. 3.00 10. (5 pts) What is the current I (in A) through the 10 S2 resistor a very long time after the switch
is closed? A. 6.00 B. 0.50 C. 1.00 D. 2.50 @ 3.00 Problem V. RC response time [5 points] 11. (5 pts) Rank RC time constants of the three RC circuits below from largest to smallest. All
resistors and capacitors have the same value. A. 123 B. 321 C. 312 .213 E. 231 Physics 1238, Winter 2009, Version 3 Exam 1, page 2 Name Student ID Number
last ﬁrst Problem VI. Driven RLC oscillator [30 points] This circuit is driven with (Speak = 50 = 100 V at resonance. R = 20.0 Q, L = 2.00 H, C: 2. 00 [JR and recall that focus wt I = / Z is a maximum at resonance.
peak peak 12. (5 pts) Argue that the impedance Z, deﬁned as
R2+ +(X— —X 02,) must equal the value of R at the resonant frequency. IM’ 4%,; lsanWd/‘NQW $0.2
ng 1:2 4;. «Minimum. 1111s hermit: XL ’Xc. > 13. (5 pts) Calculate the value of Ipeaka 1W: .gk AL“ 3.: 5424 41— wsamu. 14. (5 pts) Determine the value of the resonant afrequency beginning with the deﬁnitions of X L anchintennsofagL,andC. = 2. I
x a» ’1: .1 warmth w—
,4.) . —" .
mm17)“:60Mm;2x10'3*5”°”*
mm = 660 He 15. (10 pts) Evaluate X L and XC , then VLpeak and VC peak, and compare their values to VRpeak X =%$L— 51/0 1'.2‘7‘13A20/11=/0z:1r1.n.=)(c_ 4;:wa
V1 wk ==.''/0w.9,x5m14 5w ’XIW4=VPa/‘ <0
>(,_=)Q_= {000.12. 6%,! VLF“: \éymLﬁ(O k'V 47" #507444“ 16. (5 pts) Sket roximate, but reasonably accurate, phasor diagram below displaying the
peak valu 8, VL, VR, 1, d be certain to label all these elements in your diagram (and make it (as big"as you can . na y, evaluate the phase difference (1) between 8 and VR. MVc V1. Physics 1233, Winter 2009, Version a Exam 1, page 3 ...
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