2004 em mc and answers

7/28/2019 2004 EM MC and Answers

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Physics C: Electricity and Magnetism

PHYSICSCSection, ELECTRICITY NDMAGNETISMTlme-45 minutes

35 QuestionsDirections: Eachof thequestions r incompletestatementselow s followed by frve suggested nswers tcompletions.Select he one hat s best n eachcaseand hen ill in the corresponding val on the answersheet.

t t l t t lt t l t t lI36. Thrce* uF caDacitors rcconnec0edn seriesasL 'shownn thediagrarn bove. hecapacitancef

thecombinations(A) :uF' z '(B) I pF

)(C)+uF J '(D)+uF' z '

I(E) +uF- o '37. A hair dryer s rated s1200W, 120V. Itseffectiventemal esistances

(A) 0.1 o(B) l0 o(c) 12o(D) 120(E) 1440O

.42.q l

.q3

ot thl.

38. A point charge +p is insidean unchargedconductingspherical hell hat n tum is nearseveral solatedpointcharges, sshownabove.Theelectric ield atpoint P inside he shelldepends n the magnitude I(A) O only(B) thechargedistribution on the sphereonly(C) Q and he chargedistributionon the sphere@) all of thepoint charges@) all of the point charges nd he chargedistribution on thesphere39, In a certain egion, he electric ield along ther-axis is givenby

E=ax+b.wherea=4OYhrPandD=4Vlm.Thepotentialdiffeiencebetween he origin and. r=0 . 5m s(A) -36 V(B) -7 v(c) -3v(D) 10V(E) 16V

734 GO ONTO THENEXTPAG


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C: Electricity and Magnetism

Questions40'41X X

X X X XA Darticleof charge+e andmass n moveswithr*"i*r" o"""taictilar to a uniform magneticield Balr""t"a ioto itt" page.Thepathof theparticle s acircle of radius r' asshownabove'

40. Which of thefollowing correctlygives hedirectionof motionand heequation elatingo andr?

X42. A2OpF parallel-plate apacitors fully chargedto 30V. Theenergystoredn thecapacitorsmostnearlY

(A ) 9x 103J(B ) 9x 10 -3J(C) 6x 10-4J(D) 2x 10 -4J(E) 2x 10-743. A ootentialdifferenceV is maintained etween'-' i*i1**". p*ullel conductinglates'An electron.tu.t. fon te.t on thesurfaceof oneplate andacceieratesoward he other' ts speed s treacheshesecond late s propodional o

ltvruJV

X

X A Bvv2

(A)(B)(c)(D)(E)Direction

(A) Clockwise(B) Clockwise(C) Counterclockwise(D) Counterclockwise(E) Couirterclockwise

41. Theperiodof revolutionof theparticle s(A)(B)(c)(D)(E)

iflcoprylng or tcu.c olol thl. prgp l. lllgd'

44. A wire of radiusR hasacurrentI uniformlydistributedacrossts cross-sectionalrea'l*p"tt;. tu* it usedwith a concennic ircularoath'of adius , with r < R, o calculatehe'maenitudeof themagnetic ield B atadistancefroir thecenterof thewite' Whichof thefollowing equationsesults rom acorrect"ppril"ai" 6r n perc's awto this situation?(A) B(2xr) = PoI

mr"Bl^'l eE2nm-E, - E"1 eB. -@-'"rtl eB

EquationeBr = mtteBr = ttw2eBr = mueBr = mtt2eBr2 -- mtt2

@) B(zxr)=",(*)Q) BQnr) = o(D) BQrR) = PoI@)B(ztuR)",(#)

GOONTOTHENEXTPAGE.


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Questions45-46

Q W - 4 QParticlesof chargeQ and 4p are ocatedonthe -r-axisas shown n the figure above.Assumetheparticlesare solated tom all othercharges.

45. Which of the following describeshedirection ofthe electric ield atpoint P ?(A) +r(B) +v(c) -v(D) Componentsn boththe-r- and +y-directions(E) Componentsn both he +t- and y-directions

46. At whichof the abeledpointsonthe r-axis is theelectric ield zero?(A) A(B) B(c)c(D) D(E) E

rlz6d copylng or llutot llrlr Dllc lr lll.od.


47. When he switch ,S s open n thecircuit shownabove, hereadingon the ammeterA is 2,0 A.When he switch s closed, he readingon theammeters(A) doubled(B) increased lightly but not doubled(C) the same(D) decreasedlightly but not halvedG) halved

48. Two conductingcylindrical wiresaremadeoutof thesamematerial.Wire X has wice the engthand wicethe diameterof wire L What is thepratio =l of their resistances?K. .

(c) I(D) 2(E) 4

(A)+(B)+

36 GOONTOTHENEXTPAG


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IIIII

49. A solidmetallicsphereof radiusft haschargeQ uiformly distributedon its outersurface'A graphof-electric- *tentiaf V as a functionof poritioo r is sho'wnabove.Which of the ollowing graphsbest epresentshe-magrritudeof the electric ield E asa functionof position r for this sphere?(B)(A)

(D)

I-----{ I

ot lhl. GO ONTO THENEXTPAGE.


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50, Two parallelwires, eachcarrying acunent 1,repeleachother with a force F. If both currentsare doubled, he forceof repulsion s(A) 2F(B) 2JTF(c) 4F@) 4JZF(E) 8r

51. A circular current-carryingoop liesso hat theplaneof the oop is perpendicularo aconstantmagnetic ield of strengthB. Supposehat theradius R of the oop couldbe made o increasewith time t so hat R = dt, wherea is a constant.What s the magnitudeof theemf that wouldbegenerated round he oop as a functionof I ?(A) 2nBazt(B't 2nBat(C) 2nBt(D') xBa2t(E)f;n"2f

ot thlr


52. The figuresaboveshowpartsof two circuits,eachcontaininga batteryof emf and ntemalresistance. The current n eachbattery s I A,but thedirectionof the current n onebattery soppositeo that n the other. f thepotentialdifferencesacrosshe batteries' erminalsare10V and20V as shown,what are he valuesoft and ?( A ) = 5 V , r = 1 5 O( B ) = 1 0 V , r = 1 0O( C )= 1 5 V , r = 5 Q( D ) = 2 0 v , r = 1 0 Q@) The valuescannotbe computedunless hecomplete ircuitsare shown.

53. A charged articlecanmove with constantvelocitythrougha regioncontainingboth anelectric ield anda magnetic leld only if the(A) elecaic field is parallel o the magneticield@) electric ield is perpendicularo the magneticfield(C) electric reld is parallelto the velocity vector(D) rnagneticield is parallel o the velocityvector@) magaeticield is perpendicularo the velocityvector

'^i-l_r= 20v, + If_l-_

+'ol-_l-=i lov'l__l_

38 GO ON TO THE NEXTPAGE


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oirilnr.oopis Pulled54. A conductingoop of wire that s initially arounda magnet s pulledaway rom tlte magnet o theright, as ndicated n the figure above,nducing acurrent n the oop. What s the directionof theforce on the magnetand he direction of themagnetic ield at the centerof the oop due o theinducedcurrent?

Direction ofMagneticField atDirection of Centerof Loop dueForceon the Magnet to InducedCunent

55. A squareoop of wire carryinga current 1 isinitially in theplaneof thepageand s located na uniform magnetic ield B thatpoints oward thebottomof thepage,asshownabove.Which of thefollowing shows he correct nitial rotationof theloop due o the force exertedon it by the magneticfield?(A)

(B)

(c)A) To the right@) To the right(C) To the eft(D) To the eft(E) No direction;the force s zero.

To the rightTo the eftTo the rightTo the eftTo the eft

ot lhir GO ONTO THE NEXTPAGE. 1


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Physics C: Electricity and MagnetismIQuesdons7-5E

+Q+9/ +a.?i

56. n thecircuitshown bove,heequivalentresistancef the luesistorss(A) 10.5 )(B) 15()(c) 20cr(D) 50 (,(E) 115O

ol thl.

+9... ii+Q+Q

As shown n the ftgure above,six particles,eachwith charge+p, areheldfixed andareequallyspacedaround he circumference f a circleofradius R.57. What s the magnitude f the rsultantelectricfield at the centerof tbe circle?

(A) 0

@) r{o 9=+xeo RlQ + 4raeoRz

5E.With the six particlesheldfixed, how much workwouldbe required o bring a seventh articleofcbnge + Q from very far away andplace t at thecenterof the circle?(A) 0

iJ2 Q4xes 83 Q2xcs L2

(D)(E)

( B ) 6' 4fteoG'+;, r *

oRQ2R2Q,R@2-+

Rz=20 dl

EoGO ON TO THE NEXTPAG


8/11


Questions 9-61

The diagramaboveshowsequipotential inesproducedby an unknownchargedistribution.A, B, C,D, and E arepoints n theplane.59. Whichvectorbelowbestdescribeshe directionof the electric ield atpoint A ?

( ) , /@) ,/(c) \(D) \@) Noneof theabove; he field is zero.

60. At whichpointdoes heelectric ield have hegreatestmagritude?(A) A(B) B(c) c(D) D@ ) E

61. How much etworkmustbedoneby anextemalforce o movea -1 pC pointchargeromrestatpoirt C torestatpointE ?(A) -20 uJ(B) -10 rtJ(C) l0 rrJ( D ) N N(E) 30pJ

62. One of Maxwell's equations an be written as. .1A0 e. as = -:{3. Thisequation xpressesheJ d tfact that(A) a changingmagnetic ield produces nelectric ield(B) achangingelectric ield producesa magneticfie1d(C) the net magnetic lux through aclosedsurfacedepends n the current nside(D) the net electric lux througha closedsurfacedepends n the charge nside(E) electric charges conserved

of tfil. GO ONTOTHENEXTPAGE. 4 /


9/11

qF*d-l63 Theplatesof aparallel-plate apacitorof cross-sectionalareaA are separatedy a distanced,as shownabove.Betweenheplates s a dielectricmaterialof constant (. Theplatesare comectedin serieswith a variable esistanceR and apowersupplyof potentialdifferenceV. The capacitanceC of this capacitorwill increasef which of thefollowing is decreased?(A) A(B) R(c) ,


10/11


68. A uniform spherical hargedistribution has adiusR. Which of the following is true of the electricfield strengthdue o this chargedistribution at adistance r from thecenterof thecharee?(A) It is greatestwhen r = 0.(B) It is $eatestwhen r = Rl2.(C) It is direcdyproportionalo r when r > R.(D) It is direcdyproportional o r when r


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Chapter V: Answers o the2004APPhysicsC ExamSection : Multiple Choice. Section Answer Key and PercentAnswering

Correctly. Analyzing Your Students'Performanceon theMultiple-Choice Section. Diagnostic Guide for the 2004 AP PhysicsC

Released xamSection I: FreeResponse. Comments rom the Chief Reader. ScoringGuidelines,SampleStudent Responses,

and Commentary. MechanicsQuestion I. MechanicsQuestion2

Section I Answer Key and Percent Answering Correctly

. MechanicsQuestion3. Electricity and MagnetismQuestion 1. Electricity and MagnetismQuestion 2' Electricityand MagnetismQuestion 3

Section I: Multiple ChoiceListedbelow are he correct answers o the multiple-choicequestions,he percentofAP studentswho answeredeachquestioncorrectly by AP grade,and the total percentansweringcorrectly.

lMechanicsItemNo. CorrectAnswer Percent Correct by Grade5 4 3 2 r

TotalPercentCorrect96 93 89 a2 64 872 D 97 92 a7 7'I 41 823 E 88 75 68 62 52 714 C 80 70 66 63 54 6B5 B 97 95 91 84 63 BB6 6 8 3 7 2 7 7 7 7 337 93 79 64 47 23 66B 76 42 23 3BI D B5 62 42 5110 E 99 98 98 96 82 961'T c 69 5'.7 57 47 35

C 61 46 42 36 26 4413 87 75 64 52 34 6614 D 45 32 2S 27 22 3315 81 61 47 37 17 53

C BB 75 60 42 27 6217 E 58 39 34 27 18 38D 75 52 36 27 77 46B 57 27 77 12 10 2a20 E 78 62 50 37 1921 E BB 70 58 4a 30 6322 B 90 85 B0 75 50 7923 C 40 22 17 14 '12 23

B 9B 97 94 B9 6325 C 56 42 34 31 26 4A26 D 73 49 33 24 17 4327 E 92 75 5B 39 17 6228 C 93 75 50 30 19 5929 C 48 21 '12 B 6 2230 c 81 61 45 34 303 1 70 41 23 11 6 3532 D 63 45 37 32 26 43c 55 41 34 3L 26 3948 30 21 '13 2835 B 61 33 23 18 L2 33

Electricitv and MaqnetismItemNo. CorrectAnswer Pelcent Correct by Grade5 4 3 2 7

TotalPercentCorrect36 E B6 BO 37 7137 a7 76 65 50 26 653B 66 55 49 43 25 5039 B a4 62 49 35 '1740 C 73 4A 22 12 6 3641 C 7B 42 23 13 I 3942 B 83 61 4A 24 4943 C 63 28 16 10 B 3044 B B1 53 37 29 23 49

E 94 82 62 3B 7365 43 30 26 17 4A83 65 54 42 24 5B48 B 71 47 33 21 10 4149 C 85 52 3B 20 5650 C 81 69 55 43 645i 7' r 32 1a 72 10 3352 C 44 29 20 15 2753 B 81 60 47 36 26 5454 48 24 16 '12 10 2555 C 83 57 45 32 24 5356 D 99 97 94 91 6f 9157 96 90 7A 49 805B D 63 36 28 23 15 3659 71 46 35 25 i6 4360 B 65 36 29 20 426 l B 61 39 31 22 16 3762 85 64 48 34 16 5463 D 82 66 53 43 27 5864 E 77 48 34 23 14 4465 E 6B 3B 25 5 3566 C BB 71 59 49 36 6467 79 55 40 27 15 4a6B D 73 37 2769 D 44 33 30 27 T7 3270 B B B8 I 3 11 I5

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2004 em mc and answers

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