FinalExam2006-04-25-07

FinalExam2006-04-25-07 - Department cfPhysica. Lehigh...

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Unformatted text preview: Department cfPhysica. Lehigh University Pliyaica El - Introductory Physics II Spring Zfliifi F ina] Exam May 3, Eiiflfi Closed Note 3:00 AM~1 ] :flfl AM Snident’a Name Recitation Section Nmnber Recitation Leader’s Name =¢gl=—W The teat is a muitjpieachoioc examination. First, check to he sure that you have twelve— page examination, including the cover sheet and the equation sheet. Please answer each question by circling one answer from the panel ofchcicea available within each question Space. Points summary Part I Part I] Part In Total 1.___{2o} 4.__{15} i._ [15} 1—90} 5._m_ [25} a._ [25} 3._ [25) a. _ [25} 9._ (15} 1t}.__ [15) Sub-Total {55) _{55) _{?c} _{2flfl} Part] («65 points} P l. (213 paints} Two charges are placed a distance T 312] em apart. One ef them has aehaIge of "IS m cm Itiiereeeuiembs, and the other has negative 1'5 +T5 at -15 “c miereeeuleml} charge. as shown in the figure. .__i_—. 15 em 1:: em A. What is the magnitude of the electric field at paint P shewn above? i.) s; ii.]4.1? x mime; iii.) 3.5 x mime; arias x mime; v.) T w mime 13. Which efthe arrows sham-i helew give the direction fer the eleetrie field at paint P? i.) ii.) iii.) iv.) v.) No field (3. 1|What is the magnitude of the force exerted on the positive charge by the negative charge? 1} 2250 N ii} 158.3 N iii] ii N; is} 552.5 N; v} 337.5 Poi. D. What is the magnitude of the electric dips-1e menith of the charges as an electric dipfile‘? i} 2.25x1ll‘5‘ C-m; iiia-1.512I><1EI'5 C-m; iii} 2.25:: 113'3 Gm; w) 1.13x1tr5 e-m; v) Ii. 2. [213 points} An isolated capacitor is composed of two parallel horizontal plates. n. The capacitor is fully charged. If a thin dielectric is inserted a short distance hehaeen the plates, how will it more when it is released? i] up; ii} down; iii} left; iv] right; 1r] stationary. B. When the potential difference across 1he gap is 95f} V, the parallel—plate capacitor holds 2.3ilx l 3'3 C of charge, with the gap in a 1raeunrn. If this gap is filled with a material of dielectric constant K = 2, what is the total capacitance of the system? i) c: ass nF; a) o: ass as; iii] C=2.95xlfl'm s; is} C= 1.1sx1tr‘“ F; we=s_ssxrc'“ F. C. A parallel plate capacitor is connected to a T5 1’ battery,F and allowed to charge fully. The capacitance of the two plates in finespace is 2.6 at". If the capacitor is then filled with a dielectric material arpamaaasr s = 5.31 a or” clr (N- ml), with the baaer am connected? what is the change in the charge on the capacitor? i} Charge increases by a factor of 15; ii} Charge decreases by a factor of 6; iii) Charge increases by a factor of 2; is} No change; 1;} Charge increases by a factor of 12. If the hatter}r is now disconnected from the capacitor, what is the change in the energy dent-sit},r within the capacitor? i} Charge decreases by a factor of ti; ii} Charge increases by a factor of 2; iii} No change; in) Charge decreases by a factor of 3; r) Charge increases by a factor of ti. 3. {15 points} The figure shows three separate pairs of' parallel plates with the same separation; the value of the electric potential is also shown for each plate. The electric field between the plates is uniform and perpendieuiar to each plate. {1} I till l (3} l dd V +15t] V at: V +200 V see V 40-h V A. Rank the pairs according to the magnitude of the electric field between the plates; greatest first. i) i=2=3; ii) l=2,3; iii) 3,2,1; iv} 11:3; v) none of the above B. For which pair is the electric field pointing to the right? i) 1; ii] 2; iii] 3; iv) 1&2; v] none of the above. C. IF an electron is released at the center of the plates (case 3); what will happen? i} remain there; ii) rnove rightward with a constant velocity; iii) move leftward with a. constant velocity; iv) accelerate rightward; v] accelerate leftward. D. The figure below shows; in cross section; three cylinders; each with charge Q per unit length. Concentric with each cylinder is a cylindrical Gaussian surface, all three With the same radius r. Rank the Gaussian srn'faccs according to the magnitude of the electric field at an}.r point on the surface. listing the greatest first. {a} -------------- . . (bl. """""""" r r- I'- i‘ +++++++ -" i} a=h=c; ii) a,h;e; iii] c,b,a; iv} a=h;c; iv} none of the above. Winch of the three cases has the highest electric field strength at the surface of the charge column? i] a=b=c; ii] a; iii] h; iv}c; iv] none of the aheve. Part II [65 points) 4-. {15 points} The figure shows {our wire loops {a= h, c and d], with edge lengths of either L or 212. All four loops will move through a region of uniform magnetic field (directed out of the page) at the same constant velocity a same A. Rank the four loops according to the maximum magnitude of" the emf induced as the},r move though the field, listing in the order of the greatest first. ilalbflLc; ii]a=h,c=d; iii}e=d,a=h; iv} e, d, h, a; v] none of the above. B. The graph gives the magnitude Bt’r} of a uniform magnetic field that exists throughout a conducting loop, perpendicular to the plane of the loop. Rank the five equal time regions offitc graph according to the magnitude of the emf induced in the loop, listing in the order of the greatest first. Bill i} a, h, e, d, e; ii) c, h=d=e, a iii) h=d=e, a, e; iv} h, d=e, a=c; v) none of the shove. C. if the speed of the loops is tripled to 3 i3 , what happens to the maximum magnitude of the emf'generatcd in each of the loop? i) hostesses by a factor offl; ii) Decreases by a factor of 3; iii} No change; iv}1nereases by a factor of ; v} increases by a factor of'l 5. (25 points} An electron is propelled into a uniform magnetic field of [LES T, with velocity 5 x in‘5 me, in a direction perpendicular to the applied field. a. What is the magnitude of the force on the electron due to the magnetic field? a r sin” n; ii}4 x Ic'i‘n; an: stir” in; a} a. E. 1|What is the radius of cun'atore of the electronic orbit in the field? i) 1115 cm; ii} I192 mm; iii} T.i mm; in} 13.57" mm; 1r) infinity. {2. What is the magnitude of the magnetic dipole moment of the orbiting election? a inane” emits; in inane” Crmlr‘s; iii)].43x1tl‘” emits; iuj2.onlfl']5C-m2fs; u}?.l$xlil']6C-m2ts; D. Suppose that the magnetic field is confined ndthin a circular cross-section ofS-crn diameter, and the electron is orbiting around the center when the magnetic field is [HE T. if the magnetic field is now decreased at a rate of tl.9><1 [1'3 Tie. how long would it take for it to be no longer possible to contain the electron within the hon? i} TELS 5; ii] 23.1 3; iii} 54.9 s; in} 35.6 s; u) infinity. E. Suppose nonr that the magnetic field is gradually.r increasing at a rate of 5x ill"3 Tia. How long still it talre to deemsse the radius to zero [i.e., to essentially.r hold the electron in place}? i) 'ltlj 5; ii} 23.1 5; iii} 54.9 s; in) 3513 s; v) infinity. 6. [25 points} The transverse displacement of a string in a standing wave is given by D = HM sin {0.35 :t') cos (4? t), where .'t and D are in meters and I is in seconds. A. What is the distance between two successive nodes? i) “15 m; ii) 5.25 in; iii) Eli] m; iv} 91} m; v) 2.9 m. E. Noting litat the standing wave consists of two counter-propagating waves, calculate the amplitude of the component waves. i} lfl.5 In; ii} Ell] m; iii] 5.25 rn; iv} III}.5 cm; v} It} m. C. Find the speed of the pattieles of the string at I = in to when t= 3.5 s. i} an ma; ii} an ma; iii} eta mis; iv} 3.3 ms; v) as tnfs. D. Let us now imagine that we have a standing electromagnetic wave in a thin fihn of magnesium fluoride {index of reflection of 1.33} deposited on a slab of glass with refractive index of 1.54. If the thickness of the thin film were Eflfl ntn1 what would he the longest possible wavelength {as defined in a vacuum} of the standing wave in the thin film? 13551 Inn; ii] Zita nm; iii)425 nni; MESH nm; v}3?5 ntn. E. A. neutron is a patticle of Ltihtlil'” kg in mass but has no electticat charge. To have a standing wave of neutrons in a one-dimensional gap between two parallel plates of gold, what would be the smallest gap thickness needed for a neutron of 1 eV in kinetic energy? Part III (79 points in total} T. (15 points} Consider imaging by spherical mirrors. A. If one wishes to produee a real image in a mirror that is upright and larger than the object, what kind of mirror would one choose? i} Convex; ii} Coneave; iii) either would work; iv.) neither would not]: B. Suppose an object 2 out teii is placed 13 em in Front of a convex mirror whose radius ofeurvetme is E em. ‘Wnere is the image ioeatedi' i} -fl.3flfi cm; 10-32? ens; iii) 5.14 em; iv} 6.14 cm '3. What is the magnification of the image formed by the minor? mus; ii} eon; iii)[l.29; ivy-0.29; v] 4113 3. {15 points} The figure shews a fish and a fish stalker in water. "i A. Which ef the Fellewing statements is eerreet? i) The stalker sees the fish near peint a and the fish sees the eyes ef the stalker near point e. ii} The stalker sees the fish near paint a and the fish sees the eyes ef the stalker near p-eint d. iii} The stalker sees the fish near peint h and the fish sees the eyes of the stalker near neint e. iv} The stalker sees the fish near peinl h and the fish sees the eyes at the stalker near neth {1. s} hiene ef the above. E. New assume the water level inereases te a level aheve neint e. Whieh statement is correct? i) The stalker sees the fish near peint a and the fish sees the eyes ef the stalker near peint e. ii] The stalker sees the fish near paint a and the fish sees the eyes ef the stalker nearr peint :1. iii) The stalker sees the fish near peint h and the fish sees the eyes ef the stalker near peirtt e. is} The stalker sees the fish near paint h and the fish sees the eyes at the stalker near peint d. 1r} Nene ef' the above. {3. The stalker eententplates using a lens. while the water level is at e, to see the fish better. He has a lens whese fecal length in air is it: ern. What weuld he the fecal length ef the lens when the lens is fully immersed in water? The indiees efrefi'aetien are 1.33 fer water and 1.53 fer the lens material used, respectively. i} 33.? em; ii} 31) em; iii] ll.'.lI en; is} 3.4% em; a} infinity. 9. [25 points} A given star is known to radiate atotal power of about 5 I lflgfi W. An observer on the Earth measures the intensity of the star as 6.52 X 10"” Win12. A. What is the alpproxirnate distance flora the Earth to the star in parsecs {pc}? Note that 1 pc = 3.139 K It} ‘5' m. .fiisstone that the star radiates light equally in every direction. i} 4 pc; ii) 11 pc; iii} 3 pc; iv) 2 pc; v} 15 pc. B. What is the rms strength of the electric field in the radiation observed from the star on Earth? Magnitude i] [1.5 ii} 4 iii} 0.15 iv} 9 v} 0.? Units Um]; ii.}nflf; iii.}m.iW; iv.)mNtC; v.) Both iii} and iv]; vi.}Nonc of these. C. A second star is thought to he nearby but the feasibility of resolving the two stars with a telescope has yet to be established. 1With a 3—meter telescope operating at 6th} nrn wavelength, what is the smallest possible angular separation of the two stars in the sky that can he resolved? o ate-no6 rad; a) scale? rad; an assist rad; iv} 2.4s1o'iraa; v) arena“5 rad. D. You have a Polaroid sheet, whose polarization axis is arranged vettically. A second Polaroid sheet is placed behind it in such a manner that its polarization axis is at a 30" angle relative to the polarization axis of the first sheet. A third sheet is added behind the second sheet in such away that its I polarization axis is at a so“ angle relative - 1" to that otthe second sheet. 1What is the Light intensity of the light after eroan all {1. tin '- three sheets when an Lin-polarized beam of light of intensity In is incident on the {U ' ' first Polaroid sheet? 1} [LSDD Ia; ii}fl.3?5 Is; iii)fl.928fn; iv)ll.21?l'fi; v) 01393 In. ll}. {15 points] A thin dielectric foil is full of eireular holes ofapproaimately 1 nm in diameter. To make measurement ofthe diameters of the holes, a hoam of electrons is seleeted as a probe of the ditu‘neter of holes by electron diflaetion. A. lrllt'hat should he the lowest value of the eleeIIon speed in the beam for this task? i)2.25x1fl3 me; a} 2.99mi me; iii]7.25x105 mts; tosaoxtotnes; v} 1.25xlflfinfis; B. To achieve the distance resolution of 1 nm or better, what should he the smallest Hnmt‘lfllfltjt in the magnitude of the eleenon momentum that must he held to? :i} Lester25 kg-mfs; a} Lt‘tfiaifl‘fl kgrmts; iii) Lesxm‘t" leg-mats; iv} lflfixlfl'gfl kg-mr’s; «a matte” tag-ma; C. Ifa beam of alpha pattieles is to he used instead= what should he the lowest 1value of their speed? J'ttt alpha particle is composed of two neutrons and two protons; its mass is 6.63x10'flkg. i]: 3.115le] me; a) 3.15 ma; iii) 3.15me me; to as: me; u) teat-mi ma; Lehigh University Physics 11 Equnfinn Sheet Spring, 2006 mmwgmnmm c mmu‘ m. Planrk‘scumtm: h magma-“'3: Gl'auiufimflmm c: mun-“NEW Fbamk'scunammfi} fi—M‘Efi 1.055 KID—“.13 Hun-gadm'sflmubet n2. amxmflmr‘ elmmn res-nuns: m. 9.11x1a"911Eg Boltzmann‘s WEIR h; 1.38 x 10‘?" m: pram rest mm mcl 1.6% 3-: 1n”: 1; charge an flmmu e 1.6M 111*"? C nautmn mimm m. 1.5149 x 10* kg m 5pm parmlttivlty an 5.35 x 111*” (931»: m" atomic mm um; 1: 1.3305 x 1:14T kg 1m spam permemmg pu 41: x m4 T mffi manna} I: m x In“ N michl yavltatbonalmlm'm 9 939an F 1 than”! r] Gum; anxfl m. 12-h—1 — 2 drag r3, 3: HA * A 1 1 1 pufdlx{1'—r':| hula "’ a ‘3'? fir‘xfim “"3 1? Ir—r'l -_. 1 “WW—W r wlmfii—L C" ummrmsauas: d5 Fan |1'-r"r_ LG” 3 50 “up” " flammnugm;fi=;—:3fi Efi...'{r1l.r Una-tail: I'd-=Ig-i-Xq fl ' - a: ,.. I..— V D: lb. I} IH=R:IL-UL-XG':E" 1", I N a; y a; 32?] an}; HGtimecmlst-amtzm fiflfi. fi=Ff 1’5'9—d—flE'ifl pzw pmrm LRthecuma-ntuufl Pi _1 1: “LL; W-J__JEL 3-1 waflfliflm flutHurHI-C u'mm I“ Pu drmr' 41:51: :r—r’. an mpmitur q I: Run“ TfluJ-IEE ,r:=f.-!|. : . a ~- - ms E . um-gflg=:um_i J h: " ‘31 Ha “’ mama:an 2132' 312KB:- Ar ,4. A: w2_h____: mmflLnFmfiflfifl Wni'knf'F-afl a: B. H, L '11- E-dhwg- fi'ni’rr circmnia‘aauefimmie slnfiuéb} — biannusbtmushlb CH4 mm aidrfle {fling AMT”, mulch-ale slutflzfimsinflcusis-hmflsln-fi i=1?“ wEaflBm-aufsnhm a: . _ V n iv: Volume ufsphere fE-flm-d—jB-cm 3*:an ‘ 1 Emma. b] a mama—+Binusinb ffi-flIan-I-pnui- E-dh ¢_B n+5 nzfl+h+cnfl4 shia+si115-2cns[—-}siu[ ) Jigfiiafi 2 2 anm 2-: a" I will =. fl ff'd'HF—n—l u”+| waflmbhuufl) {HLH'J swagfii "*1 d1: 1 min “d7” * P 1 f—-—-—- --]J'J{:I-]-Em]I m=1umir+uE Irv-“31311213.!!! fl! +1] a+bu I: in .._..,,«ru (2) f f E1+ll a r: a : 1,: I will 1 a :I fhlfltfunulnur u Wizadflmf 51131359“? 9 9:513“: +"} {I u :1 +H 2 :I- l'l Ems-“m mm; 23:23. Hum ICE—mun fix '1‘ at” E n I H: 3-H 1._(nsm;sjm 1 X 3” ‘mwml' 1"” “’ “fl SEEEXB’ flwfirfih {brain e'”==w9+:siufi his: [Txparim §-&w=E€-%£BE 1"“? ‘”3'°=fi"’ . 1 11 Ill] 52 51$ I 5'}; —={fl—t _+ .r “1-2:! Erik-In Ififlfifl-‘Efifl-fil‘llll _fijfi**fifi' f RI Rt! {HI -- {weightic 2|“: Fl] 11 ...
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This note was uploaded on 09/06/2010 for the course PHYSIC 021 taught by Professor Ying during the Spring '10 term at Lehigh University .

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FinalExam2006-04-25-07 - Department cfPhysica. Lehigh...

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