PH222-Su10-Exam2-SolutionRD

PH222-Su10-Exam2-SolutionRD - Physics 222, Summer 2010 EXAM...

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Unformatted text preview: Physics 222, Summer 2010 EXAM # 2 Monday, July 12, 2010 Name (Printed): 50 /M Zé/FO/i Section Number: Recitation Instructor: INSTRUCTIONS: t. This is a one and one half ( 1 1/2) hour exam consisting of 25 multiple-choice questions. Each question is worth 1 point. 1 will count your best correct answers for a total of up to 25 points. Use your previous bubble sheets answering questions # 26 through # 50. 2. Use a number 2 pencil when marking your bubble sheet. Do not use ink. Ask for a pencil if you did not bring one. Fill in the appropriate bubble completely. It you need to change any entry, you must completely erase your previous entry. Also, circle your answer on the exam. 3. Carefully read each problem and its five possible answers before beginning to work on the problem. Select only one answer for each problem. Choose the answer that is closest to the correct one. 4. Before handing in your exam, be sure that your answers on your bubbie sheet are what you intend them to be. You should copy down your answers on a piece of a scratch paper for comparison with the answer key to be posted later. 5. When you are finished with the exam, place all exams materials, including the bubble sheet, the exam itseif, and scratch paper that you used for the exam, in your folder and return the folder. Good Luck! -- Art Meyers 26] Which of the following four statements about the results that come from the generalized concept of flux change with respect to time is FALSE ? A) An iron magnet thrust in or out of a coil connected with a galvanometer induces a current while the magnet is being moved, the direction of the current depending upon the direction of the magnet motion. B) An electromagnet brought up to the coil similarly induces a current during the motion of the electromagnet. C) The insertion of an iron core in the electromagnet also induces a current. D) Opening and closing the circuit of the electromagnet while it is held steady near the same coil induoes currents in the coil due to the changing flux associated with the changing current in the circuit. @311 of the above statements are TRUE. 2?] Magnetic forces are found to obey laws similar to those governing electrostatic forces. In fact, much of the same kind of language and similar concepts are used to describe electrostatic and magnetic phenomena. Which of the following four statements is FALSE ? A) Magnetic effects have been attributed to so—called magnetic poles concentrated near the ends of magnets. Instead of referring to positive and negative poles, it is customary to distinguish between north {seeking} and south {seeking} poles. 8} Like poles repel and unlike poles attract. C) The magnitude of the interaction between two magnetic poles m1 and m is given by Coulomb’s law of magnetic attraction: F = ( m1 m2 ) i‘( u r2 ) . where r is the separation and u is a quantity called the permeability which is characteristic of the medium between the poles. @ There are no magnetic effects unless there is a moving charged particle in the field. E) Q of the above statements are TRUE. 28] Two wires that are parallel to one another are separated by 1.0 m, as shown in the figure. Each carries a current of 3.0 A, but in opposite directions. Find the direction and magnitude of the magnetic field at point P midway between the wires { Bp }. A) Down 7.54 x 10‘5 T Iii“) P I (out) -~ 69 x @Down 2.4x 1061‘ G l<——-—————— 1.6m ———.pl C) Up 7.54x10'E’T E) The magnetic field: 3;; = 0 291 Which of the following is an accurate statement“? he magnetic force on a moving charge does not change its energy. B) A current carrying loop of wire tends to line up with its plane parallel to an external magnetic field in which it is positioned. C) The magnetic force on a current carrying wire is greatest when the wire is parallel to the magnetic field. D) A magnetic field line is. by definition, tangent to the direction of the magnetic force on a moving charge at a given point in space. E) Magnetic field lines have as their sources north and south poles. 30] An ion of mass m and of charge +e is in circular orbit around a fixed point charge Q, with charge -8.0 pic. The radius of the orbit is 0.20 m, and the speed of the ion in the orbit is 1.2x106 mfs. A uniform external magnetic field. perpendicular to the plane of the orbit, is present. The magnetic force on the ion is equal to the electric force in magnitude and in direction at all points of the orbit. In the figure, the mass m of the ioa is closest to: A) 6x10 '26 kg B) 5x10 '2“ kg 4x10 ‘2‘ kg 8x10 '36 kg 7x10 ‘25 kg .2 . (.‘t No! lorce2m— = qu + k i _‘ '_> Hi 2 r1" UQXH .3): liter; _ 2X9><Hluxlti><lll "l IV=123<105mIs e 0.20me o x-aopc t’t’ .. . = 7i“ (because I}; = h} r i r" ’xhxlt)“ a s x l n ““A-g The correct answer is option DJXX l l) Whig 31] A circular coil of wire of 200 turns and diameter 5 cm carries a current of 4 A. It is placed in a magnetic field of 0.70 T with the piane of the coil making an angle of 30° with the magnetic field. What is the torque on the coil? A 0.48 Nm .95 Nm C) 1.8 N.m D} 0.55 N.rn E) 2.5 N.m . rs fl" . . azm- :3.|-—1><{ :xltl' || :l.%>«|(l ‘m 1' : ,-'\-".-’.tlb’ sin 6’ : ltltlx—Lx ! .on It} 'i Xil.7{l><sin (10" = 0.95 N111 ("orrct‘l answer is option b’lllflfi NJ]! 321 The figure shows a velocity selector that can be used to measure the speed of a charged particle. A beam of particles is directed along the axis of the instrument. A parallel plate capacitor sets up an electric field E which is oriented perpendicular to a uniform magnetic field B. If the plates are separated by 2 mm and the value of the magnetic field is 0.1 T. what voltage between the plates will allow particles of speed 5x10S this to pass straight through without deflection? A)310V B)630V C 16V r v“ 100v ‘- - r: , _ a _ .:.__-__ _ 1__.:..: _ j ‘ EHZV ‘ B H _:> 18:! oxlt) xtl.|><_><|t} (cutaway x 2 It)“ Will Tube (into paper) 3': r—EI 36 X Vlewj\ :c ‘_ K Capacitor plates > H} liltiV is answer. 33. Two very long, vertical}, current carrying wires intersect the x axis at —4 cm and +4 0111 as shown. At which point will the magnetic field have the largest magnitude? e-..” M. .emflfiméfiq . ____. .-____..q,_ B) B fee f7wfl7’7/ 34- A brick-shaped object with dimensions 1.0 cm >< 0.1 cm x 0.] cm is made of some ohmic material with resistivity 1.0 x 10‘7 Q 111. What is the resistance to an electric current flowing along the long side? A :- /. a c». r /0 m L f “ _ _ _ _ _ _ fl ‘I I 10—1 9 K :_'" W Z I If; , 10-3 o h; /0’.’ m __ . ' c.1049 23/0/11?“ i I I D. 10'9 o /:7 I44 I ' E. 10‘11 o ___ x; z l A _~ (0:!) _ . . 3 2 " b ‘1 35- Pour identical bulbs are connected in a circuit with an ideal battery as shown 3 0 ) 2 /0 W below. 7'. "r I; fj1+fl£3 _ 6W4, aw I$¥/¢ é}gZ‘/€!{ -' —-— ya at» 1‘34: (2—39 47 "n __r . firm-LA “PM Rankthe br1ghtnessBofbuibsl,2and 3: ma “,5 .. Kid/.4; #2. 313.323'33 a B. 31>32=B3 w. 62 7’93 C. 31533332 D. 81:83583 E. 31:32433 36- The circuit below consists of three resistors and three ideal batteries. Find the current through the 2.0 Q resiStance. A 1.4A . 1; @12A T45 W t’?’ ) (I 4.3 A {kinks Owl“) 1_\. 2.0 o D 5.0}; v - E; 10A ééfifiwlfid 5‘; s ‘1 C Z. ___,_. 5.09 10V m/e’ (z =‘ 2‘ Mir": 20'"251“§° 5/0”“? 30"2‘zfl‘w—flm _'/D:O 10V 37- . A solid wire with a circular cross-section of radius 30 mm carries a total current of 10 A out of the page. The current density across the wire is uniform. What 1s the magnetic field at a point 15 m away from the center of the Wire? .H ..- . ._ a mi A)0 6‘11? :flvfind if 6077’} fl 1? B) 0.015 mT 7, @0033 111T _ ‘ __ :- :1 D) 0.13 1111‘ I 5mm? waft—’(re/w fl?) “'9’ I fit? E) 017m WW fr: I 1 :: .L.._....—-—-' p", r:/l/MM£ K: 3pm,)“, ' j-(fir ) K2 % .a o: 1’ fl; '" {ii V C'mzodecww) 1“ K 2:” ’4. 2w— w _. ,. g WX/MAUM) era/(m2 r (2.033 M ’ ' 2,7}, ((9 .0391“) 38] A studenI needs to make alsolenoid that produces 1.08 T at its center. He will wrap a wire around a solid cylinder of iron with a relative permeability Km of 1400, a length of 16.3 cm, and a radius of 1.92 cm. If the wire can carry a maximum Current of 1.28 amp. the number of turns of wire needed along the entire cylinder to produce the desired B field is closest to: A) 8 B) 300 ' C) 5% _, .. Lox )7 5’: ,un! : Amfiunl = | ,081‘ —3 n — — :480 7'8 ' I4tlflx42r>< IU xl.28 N . n: ’1'_:>1"Vzfii: 48(1xl63xll)‘ = 78 391 In the figure. an insulated wire is bent into a circular loop of radius 6.0 cm and has two long straight sections. The loop is in Line x-y plane. with the center a M at the origin. The straight sections are parallel to the Lexis. The wire carries a ' current of 8 A, The magnitude of Lhe magnetic field at the origin. in 1.11", is c osest to: - . 9-" ' _ ) 80 - - C) 110 o) 100 n A a” E) 70 b’ 2 KW + .1 2 of! K _ #1.! I. -r: 32m .V : 4mm "XS; 4rxm"’xs n, Exam}: Eirxexm'” : _x4xro "w? — 30.?x 1 U _}' -_>I H I: 6843 + £77 x m “ : 88M . A» The closest answer is A) 90y)". 40] A long straight wire on the y—axis carries a 10 A current in the posltive y-direction. A circular loop 0.50 min radius, which is in the y—z plane, carries a 9 A current, as shown in the figure. A field point P is on the positive x-axis, at a distance of 0.50 m from the center of the loop. The magnetic field at the field point P is closest to: A (-4.0): lO'ET)i-(8.0x 10%)}: (—4.0): 10hr) i — (4.0 x lD‘E’T)k C) (-8.0x 10'51')k D) (+4.0x 10"T)i—(4.0x 10'5r)k E) zero ,trflimu" I: I“ [L n _ 1 "‘ , H‘ l,__ “_ |'-I<' 3h" +tr‘ l"' Zita“. saxm‘xuxos-‘q 42rxln‘xlo __ __ , . 2m.5-‘ +0.53": :8 : -I'.'r a = 1i 22r><ll5 = —4><m “i—-1><|ll“i:':if} islhcanswer. plastic rod \ 41} An uncharged metal rod is resting on a small stand that is free to rotate. When a negatively charged plastic rod is brought close to one end (A) of the metal rod, the metal rod is attracted toward the plastic rod. \‘ Assume now that the negative rod is removed, and that I$ instead a positively charged plastic rod is brought in B A turn close to each of the ends of the metal rod. gin—5:: rotating stand Which of the following best describes the behavior of the rod? ' A) There will be neither attraction nor repulsion of the metal rod (it is uncharged). B) The metal rod will be repelled when the plastic rod is near end A, and attracted when the plastic rod is near end B. C) The metal rod will be attracted when the plastic rod is near end A, and repelled when the plastic rod is near end B. D The metal rod will be repelled, whichever end is close to the plastic rod. The metal rod will be attracted, whichever end is close to the plastic rod uncharged metal rod 77w f/ggzl/C wife/arises £45 ICE/large! (1,. 6,46 mafia/ Vac/J mic/ ZMM‘ a/weys mesa/{5 M a; hefi fifiraeffo/g, 42. A uniform magnetic field of 1.2 mT is directed vertically upward A proton with velocity of 3.2 x 10? m/s enters the magnetic field volume from south to north. What magnitude defl eating force acts in the proton wgle it is in the magnetic field? The proton mass is 1.67 X 10‘27xkg. . 5:: WK 8 A) 6.41X10'23N 2‘ B) 3.05X10'15N .59 L a I 7 f/J‘ ?a d /'V-’fg_ C) 6.10X10‘:N @ fl/ 3 ,3 n 13.13110 N F: (M); x,p“’4c)(3’.zxm 144/5)(/.Z7{/JT None ofthe above “A, ' h A, I F=6./(X/o T :- éth/o A/ 43. A flat surface with an area of 4.0 cmZ-is oriented W'lfll the surface at an angle of 30° with respect to a uniform magnetic field. Ifthe magnetic flux through this area IS 0.75 me. Calculate the magnitude of the magnetic field. Amt JG ‘-'-‘ 3/4 B)1.88 T we , *7 c 2.17 T _ 6:. 3:3 2. 9* WIN” M ,3757. £193.75": ‘“ - ,- e r Notenoughinformanonis given. A0” aXJE :: 3',.e75’7~ 44‘ Two very long wires carry 2 A and 4 A currents as shown. What is the magnitude and direction of the magnetic field at a point located halfway between the two Wires? A) 1.2 >< 10‘6 T into page B) 1.2 x 10'6 T out ofpage C) 0T D 4.0 >< 10‘7 T mm page 4.0 x 10—7 T out ofEage I) xix/J ‘6 More WW ‘3? f L?“ Z, E 6 "A: W) 1., 1/0 a_ a 1/0 ' * I 517)”) 2;? F 7777 -,- )p“77' 4..» jaw) // tr ,. f: + 75’5": L x : WU" ’ g)- ‘J “4' ,3”! — ’f' 2:; 7” f 45. 46. Shown in the figure is a flexible wire loop lying in a frictionless tabletop. The Wire can slide around and change its shape freely, but it cannot move perpendicular to the table. 1 w it” i final/38%;. (fie/M Aim; gm'mi‘cwrs éfiélé a/g—r- ' " " "‘ 'M/f *2/12 meafiu‘a ' Z fear/nesfim {woes ref” 6;? ‘ eAg/m/fi (we H; “We; pm//€/_fi-//wa !‘ *fl/;cg'm£h ¢ Two separate actions are being censidered; (1) A current is first made to flow through the loop counterclockWise. (2) Later a current is now made to flow through the loop clockwise. For each case determine the behavior of the Wire. Which pair of choices below is correct _ for the behavior of the Wire? Clockwise Connterclockwise A) Wire stretches out into circle B) contracts into clump contracts into clump Q contracts into clump _ a Wire stretches into circle _ wire stretches into circle . There is not enough information to tell what happens. _ contracts into clump _ wire stretches out into circle Which of the following four statements about magnetic field lines is FALSE? A) Magnetic field lines leave the N pole of a magnet and enter the S pole of a magnet B The magnetic flux is the number of magefic field linesfunit cross sectional area. Magnetic field lines can cross one another. ' The more closely spaced the magnetic field lines, the stronger the magnetic field. E) _A__l_l_ of the above statements are TRUE. The simrm'an below pertains to the heir two questions: a: W A squarloop (side 20 cm] with a current of 0.3 A running in the -- direction is in the plane of this page. There is a maiform magnetic field of 2.0 T parallel to the page but at an angle 01°30D with the horizontal direction. 47- What is the magnitude and direction of the magnetic force on the right side of the square? " A) 0.060 N intothe page B 0.060 N out of the page C) 0.10 N into the page 0.10 N out of the page E) 0 I: dz: F f If; {3" .-_— 1/41/57 53,-” 5’ a I I r: Z- ;r/x \ ’ - WMKZW 5"“ 5" m m, dam r J {9 0 M‘Vl‘l/ :rZ/o/LHHJSM 48._ What is the magnimde of the torque on the loop? A)_0 {fig/MIN; 9% KM Myekflafize @¥@ B 0.012Nm my: part? waafygr 9,4,3 @¢@ W7 C) 0.021an ' _ , _ I D) 0.024Nm flggfimé HQWaW/J’py E)0.048Nm f0i0éfi/ I ‘Y - .: /€V€Vfiym kid/[g / I 3’: l (D (plinth )fz. : I .2 , I. - (0 29-2369. mm) -= 671ng)” _ 49- Imagine a wire loop running along the edge of this paper carrying a current in a clockwise direction around its perimeter. Tfthere is a uniform magnetic field applied perpendicular to (and out of) this page, the interaction between the field and the current will: ' Tend to pull the wires inward. Tend to push the Wires apart. D) Tend to rotate the loop around an axis through the center of the page and parallel to the top edge of the sheet. \ E) Tend to rotate the loop around an axis through the center of the page and parallel to the left edge of the sheet. @Do nothing at all, there- will be none. ) 50‘ . The figure shows the paths of four particles. They all have the same charge 9 and initial speed v. They are in a region of uniform magnetic field out of the page. Which particle has the largest mass? A)A BJB C C D . Cannot be determined from data given. 7W5 f/fIfi/T'W ’W’LE =5? 7W6"— gmfgénam 17/ W5 #erM6 @510 M” WWW— P 15 gaww (my? (fan; warm?) =3 Fairer: #529. 3mm“ mm mm» cflzwry 77w fiflflar Garfiféwé Aim flag»? 3” 13' awn gamma" Fro/*7 {1’ WW iwefifis f AI 6m flaw 3/9: 13" ...
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PH222-Su10-Exam2-SolutionRD - Physics 222, Summer 2010 EXAM...

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