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Unformatted text preview: Exam 2  White version
Physics 2760 Last Name E First Name lD# This is a closed book exam. I understand, pursuant to University
Regulations on academic honesty, that I am not to use any notes or
information other than what is in the official, non—annotated
formula sheet. Signature For multiple choice questions, please make sure that you circle the letter for the answer which you believe to
be correct and only that answer. If more than one answer is circled for the same problem, you will not receive
credit for it. Don’t get hung up on questions. They should take only one or two minutes each. If you find
yourself spending more than a few minutes on a multiple choice question you are probably looking at it the
wrong way. You should skip it for now and come back to it later. For full credit show your work for solutions to questions that require calculations. Explain from where you
start to solve the problem and show your math flowing from it for full credit. No shown work, no credit! Relax, read carefully, think — and then read everything again. During the exam, if you have questions please raise your hand and the TA or the instructor will come to you
and provide help. 1. (5 points) Capacitor B has onehalf the capacitance of capacitor A. How does the charge on capacitor A
compare to that on B when the two are connected in series to a battery for a long time?
a) The charge on capacitor A is one—fourth the charge on capacitor B.
b) The charge on capacitor A is onehalf the charge on capacitor B.
QD The charge on capacitor A is the same as the charge on capacitor B.
) The charge on capacitor A is twice the charge on capacitor B.
e) The charge on capacitor A is four times the charge on capacitor B. The two questions below refer to the circuit shown in which four identical bulbs are connected to a battery. (The switch, S, is initially
closed as shown in the diagram.) 2. (5 points) Which of the following correctly ranks the bulbs in brightness?
a) All bulbs are equally bright. b 1 is brightest. 2 and 3 are equally bright, and each is dimmer than 1, and 4 is dimmest.
<55 1 and 4 are equally bright. 2 and 3 are equally bright, and each is dimmer than 1 or 4.
d) 2 and 3 are equally bright. 1 and 4 are equally bright, and each is dimmer than 2 or 3.
e) 1 is brightest, 4 is next brightest. 2 and 3 are equally bright, and each is dimmer than 4. 3. (5 points) Which of the following correctly ranks the currents flowing through the bulbs?
a) All bulbs have the same current flowing through them.
b) The current through 1 is largest, 2 is the same as 3, and each is smaller than 1, and 4 is smallest.
@The current through 1 and 4 is the same. 2 is the same as 3, and each is smaller than 1 or 4.
d) The current through 2 and 3 is the same. 1 is the same as 4, and each is smallerthan 2 or 3. e) The current through 1 is largest, 4 is next largest. 2 is the same as 3, and each is smaller than 4. 4. (5 points) Which of the following correctly ranks the potential differences across the bulbs?
a) All bulbs have the same potential difference across them.
b) The potential difference across 1 is largest, 2 next largest, 3 next largest and 4 smallest.
G3) The potential difference across 1 is the same as 4. 2 is the same as 3, and each is smaller than 1 or 4.
d) The potential difference across 1 is the same as 4.2 is the same as 3, and each is bigger than 1 or 4. e) The potential difference across 1 is largest, 4 is next largest. 2 is the same as 3, and each is smaller
than 4. 5. The capacitor in the figure below is initially uncharged. Consider that switch S is closed at t = O s. a) in the space provided below, draw the 8 = 38 V equivalent circuit fort = O s. (3 points) RI=6Q
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R3229
C=5yF c) immediately after the switch' Is closed, what Is the current through the resistor R1? (4 points) :i:§; =:§c #53::511 d) Immediately after the switch Is closed, what Is the voltage across resistor R1? (4 points) W, «a m w :61 e) Immediately after the switch is closed, what is the current through the resistor R2? (4 points) v;:12L e,v :5‘17 L VL ’7)
3w 2/ f) What IS the current in the circuit after a very long time has passed and the capacitor is fully charged? (4
points) 0L : ; HQ" ' ‘— ﬂvﬁ 19 .&\\C 96 me 913:» «\‘m Cum E mg HRNDWQM (Pp g) What IS the voltage across the capacitor when it is fully charged? (4 points) VC: v; E'V\ "—‘ EE~'1.(B\ ~ 28— (21300
We: 2M \/\ h) What is the final charge on the capacitor? (4 points) 6. Write Kirchhoff’ 5 Laws (or use the mesh method if you prefer) for the circuit provided below. Make sure to
indicate the direction' In which you go around the loop. (20 points) 7. A 2 x 1012 F capacitor is charged to 3000 V and then removed from the battery and connected to an
uncharged 5 x 1012 F capacitor. a) Make a drawing and specify if the capacitors are connected in series or in parallel. (5 points) 33E? Jill—HS“ AM we chmec 3w 3
2, ' _,__, m . x \3 :3 > Bra WKE
’—33E:’ 4&2 3 CQ? L3 3 \TG \ K3383 .
b) What is the new charge on each capacitor? (6 points) )Q: {3&3 (X; C V: bu [\7 (17K3333233%00®:
V r‘x \ . \ 3 1 I L/\j3 __ #2...—
3V3: Z 3:3 v £5,132: 2% 03¢ EMU—~32, 03 o) (W R A ‘03
;> cm [xx—t (Q2 \ QM, ; “2),;ch ﬁt), I m to c,
3&>RSQ\ IX H&ruaxm C c) Find the initial energy stored in the 2 x 10'12 F capacitor. (6 points) ...,...._.
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3? ”” glﬂlwﬂrwm’ e) ls potential energy gained or lost when the two capacitors are connected? Where does the energy ”go”? (2
points) 7%le (‘ka 3m Muen3v3. Awe 3% Wem‘cmgfz QM ka‘wxgc; l MC 05 Q6 Q7 l Total [20/ 35/ 20/ 25/ [100/ ...
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 Fall '08
 kozstin
 Physics

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