test3_solution - Problem 1 (8 pts) +++ +++ ’ ++ —f—+...

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Unformatted text preview: Problem 1 (8 pts) +++ +++ ’ ++ —f—+ +++ & & ‘ +++ ++ +++ +++ C A + B The diagram shows a section of a circuit where a long, straight thick wire and a long, straight thin wire are connected. Both wires are made of the same material. A steady state current flows through the circuit, with electron current moving to the right. This section of the circuit is far away from the battery. A student has drawn the distribution of surface charge on the wire, sampled at three equidistant locations, and the electric fields inside the two wires; however, there is at least one error in the student’s diagram. Diagnose the student’s diagram by answering the following questions. Circle T for each true statement, and circle F for each false statement @ F The electric field E1 in the thick wire is in the wrong direction. @ F The electric field E2 in the thin wire is in the wrong direction. E2 (thin) should be smaller than E1 (thick). T T F Since this is a steady state, both electric fields should be zero. (9 F The magnitude of the change in surface charge density from B to C should be larger than the magnitude of the change in surface charge density from A to B. Overall, as you move from A to C, the surface charge should become less positive, not more positive. The amount of charge at A, B, and C should all be the same. There shouldn’t be any surface charges on the wire at all, since the battery alone creates the electric field. Problem 2 (4 pts) y A negatively charged chloride ion moves in the positive x } direction. (+x is to the right, +y is up, and +2 is out of the Q69 ( ' a) page.) Draw or indicate the direction of the magnetic field i made by the chloride ion at the four locations marked by an a “x”. If any are zero, say so explicitly. : Problem 3 (19 pts) A coil composed of 20 turns of wire, of radius 0.03 m, is connected to a battery by wires not shown in the diagram, and current flows in the coil. Consider the center of the coil to be the origin; North is in the +x direction. A compass placed at < 0, 0, 0.08> m deflects 65 degrees to the West, as indicated in the diagram. (a: 15 pts) What compass deflection, magnitude and direction, would you expect to see if the compass were moved to location < 0, 0, —0.28> m? Clearly show all steps in your work and reasoning. If you make any approximations, state them. Boon. : BéMrl-I ta" 6 3QQ'S'T)‘CAW (’5 : £1.27e‘5’7’ M ,21' 71R?“ : : A/ ,....° ____.———-————— 6”" NBLW’ em (2‘ +122)?”2 3 / ” BCOIL (%1+K2)3(1_ 52292-5 T) ,ng+ ‘0325 ; N33) (97ml) 930(/e’7)(2)[r7)(,03)z AT [21: 0.28: \ |l L g = 1:; 2mm" : .20 xe—7)(2>(2.373(n>603) d266,- COlL Hn (31+E1)3lz 4- I —6 — BC ‘ —‘ )3 _l{/.2C > ‘ _ o L. : con. _: t n . tan-t9 BEAN” ) 9 tan {Be—MTth a 2'0€_5' 9:3,5’30 TO THE W757 (b: 4 pts) Location P, indicated by a dot on the diagram, is inside the wire and on the y—axis. Draw an arrow indicating the direction of conventional current flow at location B. Problem 4 (29 pts) A circuit contains one battery and two wires in series, as shown in the diagram. The two wires have different lengths and are made of different materials. Wire 1 is 9 cm long and is made of a material whose electron mobility is 3e-4 (m/s)/(V/m). Wire 2 is 15 cm long and is made of a material whose electron mobility is 1.2e-4 (m/s)/(V/m). Both wires have cross-sectional area 4e-6 m2 and approximately 8e27 mobile electrons per cubic meter. The emf of the battery is 2.4 volts. (a: 15 pts) In the steady state, what is the magnitude of the electric field in wire 1? Show all steps in your work. ¢I:(,2_ ~9Vl/iu,t’:,:“/4“7~tz ; “lei: (42.51 “I ‘5 l E2: (41 (b: 5 pts) In the steady state, what is the magnitude of the electric field in wire 2? Show all steps in your work. (3 ., __.__' E —-,,________..— ( [6)! .2. I L269) 5. m) m “a. (c: 5 pts) How long would it take a single electron to travel from the negative end of the battery all the way around the circuit to the positive end of the battery? Show all steps in your work. V: = V; = “QE; = (me—L001?) "vs = /. fife—3 "v; L, +1.2 ,O‘im-i—,/$‘,.1 ffgs _ ~ _— /. 5'5'6'3MA. Z tl—rtt: ill—+£— : 2. tTOT‘ L. V ‘ V2' V2 (d: 4 pts) How many electrons per second cross the junction between the two wires? Show your work. {53¢}: nszt (S’e17)(‘/e—c)(/.sse~3wa/s : v. 75 e /7W.M~ S ...
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This note was uploaded on 02/08/2009 for the course PHYSICS 2212M taught by Professor Weisenstein during the Spring '08 term at Georgia Institute of Technology.

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test3_solution - Problem 1 (8 pts) +++ +++ ’ ++ —f—+...

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