ES2F11 - 10. 11. 12. Physics 227 — Hourly Exam 2...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 10. 11. 12. Physics 227 — Hourly Exam 2 Thursday, Nov 17, 2011, 9:40 PM — 11:00 PM ARC-103 (A-I), SEC-111 (J-M), PLH (N—R), Beck Aud (S—Z) Your name sticker with exam code Use a #2 pencil to make entries on the answer sheet. Enter the following ID information now, before the ewam starts In the section labeled NAME (Last, First, MI.) enter your last name, then fill in the empty circle for a blank, then enter your first name, another blank, and finally your middle initial. Under STUDENT # enter your 9-digit RUID Number. Under CODE enter the exam code given above. Enter 227 under COURSE. You do not need to write anything else on the answer sheet for now, but you may continue to read the instructions. During the exam, you are allowed one 8.5 x 11 inch sheet of paper with .7-.Whateverwyou‘want“writtenonnit.--N.O.Calculators,iNOACelehones.. r, The exam consists of 16 multiple-choice questions. For each multiple-choice question mark only one no deduction of points for an incorrect answer, so even if you cannot work out the answer to a question, you should make an educated guess. If you have questions or problems during the exam, you may raise your hand and a proctor will assist you. If you need the value of a physical constant that is not given, we will provide it. It is your respOnsibility to know the relevant equations. A proctor will check your name sticker and your student ID sometime during the exam. Please have themready. You are not allowed to help any other student, ask for help from anyone but a proctor, or change your seat without permission from a proctor. Doing so will result in a zero score for the exam. ' When you are done with the exam, hand in only this cover sheet and your answer sheet. ' Please sign above by the name sticker to indicate that, you have read and understood these instructions. “ Useful Information k = 1/4neo = 8.99 x 109 Nomz/C2 ; no 2 4n x 10‘7Tm/A; milli=10‘3; micro==10“6 1. For a lecture demonstration, a physics professor plans to hold an uninsu— lated current—carrying'wire in her hands. For safety, the potential difference between her hands is to be no more than V. She holds her hands separated by a distance of L, with the wire stretched tightly between them. The wire ' is to carry a current of] and is-to be made of aluminum with resistivity p. What is the minimum wire radius that is consistent with safety? Y,r—-§”:/: , <%> ) p / / c) x/T—pL $7) V lg. L» d) »‘/Ip/V7'r V Tr“ e) No radius is safe because no voltage is safe. *2. An emf source with a magnitude of 100 V, a resistor with a resistance of 100 Q, and a capacitor with a capacitance of 2 micro—F- are connected in series. What is the time constant of this circuit? ‘ 3) 3:10:38 take, sélolfl>€2>00 a") g; 'ZXiows' e) 1s 3. The magnetic field in a certain region is 0.10 T and its direction is that of r-Athe~~+z~axis~-i~n--4the~rfigure;il‘hrough--whieh~:-of~thesurfaces-ofthis—triangular-~-»~~«~--- -- I bloc1< is the magnetic flux zero? ' . "‘33 ~=a ' ‘ 3“ B" S O ' y W ‘M Kai/2 WV/W/Mé‘wr éaazxe 0 t a) surfacesabe and cdf only ' b) None of the surfaces c) Only through all five of the surfaces together Surfaces abc‘d, abe and cdf and all five of the surfaces together e) All of the individrialsmfaces 4. Two long straight wires are separated by a distance of x. The force per unit length that each wire exerts on the other is F and the wires repel each other. The current in wire-1 is I. What is the current in wireo2? ~— .... ~—/ lawn/pg] jig—e :3 F S BLEE— c‘ Fat/[.60] arr/X d) 27er/MOF . a... w. paw/,0: 5. Consider 3 different light bulbs, with resistances RA, RB, and RC. When ' all are connected in parallel to a 120 V source, they have power PA=60 W, PB=75 W and PC=100 W. Which statement is true? RB is largest. ? 1‘: i2 (R '5; R @ RA is largest. r) ' A ‘ c RC is largest. 45W 5) Fa d) The resistances‘are all the same. The brightness depends on the PA gum/1M1— current instead. e) It is impossible to tell from the information given. 6. A beam of singly ionized carbon atoms (14C and 120) is injected into the mass spectrometer shown in the figure. The ions all have the same veloc- ' ities and charges. The 140 ions follow the trajectory illustrated, bending downward in a vertical plane. Initially the spacing between the 14C and ""120‘io’fis’in' the verticatdirection "is ”Ay’.’”""1f"the" magnetic field‘strength‘of’ ' " " ‘ “ the spectrometer is increased, which statement describes the relationship between the 140 and 120 ions. ' [l a) The spacing Ag stays the same, with the 120 ions above the 14C ions. ‘ b) The spacing Ay increases, with the 12C}‘ ions above the 14C ions. c) The spacing Ag increases, with the 14C ions above the 120 ions. d) The spacing Ay decreases, with the 14C ions above the 120 ions. ' a The spacing Ay decreases, with the 120 ions above the 14C ions, - r026) flaélluitv/ ‘25 ca [ECW’L'LQ M .. - V‘H , 11» =1 ( V 7o©llcalmer 561;wa ( chi/{4%) (Qt: nus) (M (We): What is the relative magnitude of the electric and magnetic) forces between . q‘ 2/ tw l h ? '2: — ' W o equa c arges g [4M0 _, quD M (M ' gee V $113; electric;i force is 'ahgtlayas irgage‘rér C 2, . t} ' -emagne1c orce1s wy.‘ a . * __-_ . f“ ‘ I .... c) The two forces are always equal. M B ‘X M0 “411000 [WVL [5 d) The electric force is never less than the magnetic force. . W e) The magnetic force is never less than the electric fo’rCe. :3) 7 T UL ' “0" f S / a O A constant current source sends a current I through a resistor R1. A second ' AA” 1, / V resistor. R2 <<R1 is connected in parallel to the first resistor. What happens ‘9 [U c, ‘ to the current I through the first resistor? g _ 2 2 E; W at f ‘ a I increases. 0 r L f) l WW!) (Lu/Yr ‘ R, (13))51 decreases, but not to 0. ’2? 45, ‘2‘ Wm: (M, Veggie/Q c I decreases to 0. d) I stays the same. M‘l‘ Lu“? VMSOQS 44‘ (la/3 A 2'2... e) Need to know voltage of current source. A rectangular coil of length L=0.20 m and Width W=O.10 m on each side carries a current of I=1.0 A inthe counter-clockwise direction. It is initially oriented in a plane perpendicular to a magnetic field B=0.50 T going into the paper, as seen in the Figure. What is thecha‘nge in the potential energy of the coil when it is flipped by 180° aroundlthe axis shown? a) +0.01o J b +0.02o J @ -0.020 J ) —0.20 J 6) .0010.) Q) g ( ‘ L=0.2m )(0 ,0 > a a“: 2:?! :EA’ 5 lflA “201"” " M M“ p A M =<&.UZ(OW\2."' _ ‘ 10. In the-figure, what is the direction of the magnetic field at point P? a) Into the page Out of the page . T“ 0) Right, the same direction as V the current in the wire. (1) Up I e) Infinite magnitude and uncle R fined direction, since it is along ‘ .1 the wire. ' l w' P ‘5" M (\OdWHV“ m' ‘ ‘ hov‘.WZthS-,DW6 Wcficac IR“, you, 11. You are given the following circuit where R1=R2=R3=105L What is the! current through resistor R1? (R .. "L + :3 ii I V/R w 1" a? R ' a) 2A 5U it? :2 120V R3 e) T‘ -— a! w . . 12. Originally the left-hand switch is closed and the voltage source charges a parallel—plate capacitor to a charge of magnitude Q on both plates. Then the left-hand switch is opened and the right hand switch is closed so that the capacitor is disconnected from the voltage source V, allowing the capacitor to discharge through a resistor of resistance R. Immediately after the right- hand switch is closed, which of the following is true? The voltage drop across the re- sistor is V. b) The current through the resis- tor is 0. . . c) The voltage drOp across the ca- pacitor is V/ 2. d) The current through the resis- ' tor is V/RC'. e) The voltage drop across the ca- pacitor is 0. win-0w chasm:th Vwaa/m :7 VR- '3 W 3.6% xv 9—7 vac v. 13. An electron experiences a magnetic force with a magnitude of 1.6 X' 10"16 N when moving at an angle of 60° With respect to. a magnetic field with a magnitude of 1 X 10‘3 T. What is the speed of the electron? (charge A B of electron = 1.6 x 10""19 C; sin30°== cos60°==1/2; sin60°=cog30°=¢§¢2§ _ we wt: ,0: , -V . 4,53 511145 c0545 :— IUEDA/mnéflfi l 7,2), F 2x106/x/3m/s ,. 2 5 W 3 ) g'figs/iygm/S UQDEQ 3 (Law-MC) \xw flog 105*(‘3 d) 0.5.x 105-x/§m/s _ e) 0.5 ><106 m/s ::-" 2X \ Db/NE 14. Long straight conductors with square cross section, each carrying current I, are laid side-by-side 'to form an infinite current sheet With'current directed “a Q out of the plane of the page the figure). A second infiiiitehurrent'sheet \ ( M f/ 0 / is a distance (1 below the first and is parallelto it. The Second sheet carries current into the plane of the page. anhgsheet conductorsperj unit : I length. What are the magnitude and“ direction of the net magnetic field at .I E (91,»; 0 ”’ noint R, midway between the two Sheets. a) zero c) 2/1an , to the left d 2/1075] , to the right ' Mon], to the right 15. You are given a Wire of diameter D that carries a-current of I to a 200—W lamp. The freeelectron density in-the Wire is n per cubic meter. What is the drift Speed of the electron? the wire? T a) 21/ Drug 35‘“: UV "U '7) 51—2 b) 41/:13212 A 9) 0L - d“ A (A °> A .-.- tip/2r: we (1 I /7rD2nq e 41/7rD2nq VD u\_~'""'"’2y\ 3:) 7 vb CD Md:- 2» I 16. An external magnetic field Bo is applied to a slab of material. Inside the material, the resulting field B satisfies the condition [B] >> IBOL We can then be sure that; a) The material is either paramagnetic or diamagnetic. b) The material is paramagnetic. ’ c) The material is either ferromagnetic or diamagnetic. d The material is diamagnetic. The material is ferromagnetic. 7:? W0de ...
View Full Document

Page1 / 7

ES2F11 - 10. 11. 12. Physics 227 — Hourly Exam 2...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online