E2F11 - 1. 2. 3. 4. 5. 6. 10. 11. 12. Physics 227 —...

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Unformatted text preview: 1. 2. 3. 4. 5. 6. 10. 11. 12. Physics 227 — Hourly Exam 2 Thursday, Nov 17, 2011, 9:40 PM —- 11:00 PM ARC—103 (A—l), SEC—111 (J—M), PLH (N—R), Beck And (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 emam starts. In the section labeled NAME (Last, First, M.I.) enter your last 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 whatever you want written on it. NO Calculators, NO Cell phones. 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 them ready. 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 = 1/47reo = 8.99 X 109 N-m2/CZ ; Mo = 4W x 10‘7Tm/A; milli=10”3; micro=10”6 game, then I:111 is...t119-srsnty cirslsior a...l921anka then enter your, ,, - 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 I and is to be made of aluminum with resistivity p. What is the minimum wire radius that is consistent with safety? a) ‘lpr/er b) y/IpL/V c) x/IpL F d) I p/ V7r 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 S2, and a capacitor with a capacitance of 2 micro~F are connected in series. What is the time constant of this circuit? a) 2 s c) 2 x 10’4 s d) 2 x 10—6 s e) 1 s 3. The magnetic field in a certain region is 0.10 T and its direction is that of the +2 axis in the figure. Through which of the surfaces of this triangular block is the magnetic flux zero? a) Surfaces abe and cdf only b) None of the surfaces c) Only through all five of the surfaces together d) Surfaces abcd, abe and cdf and all five of the surfaces together e) All of the individual surfaces 4. Two long straight _wires are separated, by a distance of 3:. 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 wire—2? I F2711: / MoI FCB/[toI 27rmI/M0F F2m/MOI 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? a) b) C) d) RE is largest. RA is largest. RC is largest. The resistances are all the same. The brightness depends on the current instead. His—impossible "t6‘”t6ll"‘ffofnw ’th‘e‘ifi‘formatioii‘ given. " L N ’ 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 ions in the vertical direction is Ay. If the magnetic field strength of the spectrometer is increased, which statement describes the relationship between the 14C and 12C ions. a The spacing Ay stays 'the same, with the 120 .I'iyf ions above the 14C ions. L The spacing Ay increases, with the 12C ions above the 14C ions. The spacing Ay increases, with the 14C ions above the 12C ions. The spacing Ay decreases, with the 14C ions above the 12C ions. The spacing Ay decreases, with the 120 ions above the 14C ions @@®@@®@ @@@%@®@ 7. What is the relative magnitude of the electric and magnetic forces between two equal charges? a) The electric force is always greater. b) The magnetic force is always greater. 0) The two forces are always equal. d) The electric force is never less than the magnetic force. e) The magnetic force is never less than the electric force. 8. A constant current source sends a current I through a resistor R1. A second resistor R2 <<R1 is connected in parallel to the first resistor. What happens to the current I through the first resistor? a) I increases. b) I decreases, but not to O. c)‘ I decreases to 0. d) I stays the same. e) Need to know voltage of current source. 9. A rectangular .011 5f iéfigthip'o’éomfiafidaiélhlw;bii6filéfilééfiéiéi;' ” W ‘ carries a current of l=1.0 A in the 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 the change in the potential energy of the coil when it is flipped by 180° around the axis shown? Axis . a) +0.010J b) +0.020J c) —0.020J d) -O.20J e) 41010 J 10. In the figure, what is the direction of the magnetic field at point P? a b) d d) @ Into the page Out of the page Right, the same direction as the current in the wire. Up Infinite magnitude and unde— fined direction, since it is along the wire. 11. You are given the following circuit where R1=R2=R3=10Qv What is the current through resistor R1 ? WQALW,mc,WMHHH,HW,MWWWWWWHWMMWMW,WM 4A 8A 40A 12A 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? w b) The voltage drop across the re— sistor is V. The current through the resis— tor is 0. . The voltage drop across the ca— pacitor is V/ 2. The current through the resis— tor is V/RO’. The voltage drop across the ca- pacitor is 0. 13. 14. 15. H"Wpoifit"R;’midifiaymldetfiieefiwthe"tifio‘slieEts ” ” - 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 of electron = 1.6 x 10"19 C; sin30°2= cos60°==1/2; sin60°=cos30°:=\/§/2; sin45° =cos45°== x/i / 2) a) 2 x 106 m/s b) 2 x 103/\/§ m/s c) 0.5 x1106x/P: m/s d) 2 x 105/x/ij/s e) 0.5 x 106 m/s 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 out of the plane of the page (see the figure). A second infinite current sheet is a distance d below the first and is parallel to it. The second sheet carries current into the plane of the page. Each sheet has n conductors per unit length. What are the magnitude and direction of the net magnetic field at a) zero 13) ,uonI, to the left c) 2ponI, to the left d) 2pm], to the right e) ,uonI, to the right You are given a Wire of diameter D that carries a current of I to a 200-W lamp. The free electron density in the Wire is n per cubic meter. What is the drift speed of the electrons in the Wire? a) 21/7anq b) 41/7rD2n c) I / 7ran d) 4I/7rD2nq e) I / «Dznq 16. An external magnetic field Bo is applied to a slab of material. Inside the material, the resulting field B satisfies the condition |Bl >> IBO|. 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. e) The material is ferromagnetic. ...
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This note was uploaded on 01/04/2012 for the course PHYSICS 750:227 taught by Professor Ronaldgilman during the Fall '11 term at Rutgers.

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E2F11 - 1. 2. 3. 4. 5. 6. 10. 11. 12. Physics 227 —...

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