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Test3Practice_2007key

# Test3Practice_2007key - Problem 1(6 pts An electron is...

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Unformatted text preview: Problem 1 (6 pts) An electron is ﬁred from an accelerator with an initial velocity in the +x accelerator _5 the circular trajectory shown on the diagram. ‘ ~ , E direction. It moves through a region of uniform magnetic ﬁeld and travels in E: T~ .89 (a: 3 pts) On the diagram draw or indicate clearly the direction of the B “'46 ‘\ magnetic ﬁeld in this region. / “To (3,46 e— (_,_Z ) . (b: 3 pts) If you wanted to make the electron travel through the region in a ‘ I straight line, you could set up some equipment to make an electric ﬁeld in the r ,' region. What should be the direction of the electric ﬁeld in the region? ‘\ , 1 Draw or indicate it clearly. ~ s ...... _ . r ' 0 o W ( ‘ Y ) Problem 2 (7 pts.) You connect a battery to a capacitor, initially discharged, and a nichrome wire (which has a non-zero resistance) in series. You wait a very long time before disconnecting the circuit. For the statements below, circle T if the statement is true, or circle F if the statement is false. F Immediately alter connecting the circuit, the magnitude of the potential difference across the length of the nichrome wire is equal to the emf of the battery. T ® Immediately after connecting the circuit, the magnitude of the potential difference across the plates of the capacitor is equal to the emf of the battery. T ® The fringe ﬁeld of the capacitor is a maximum immediately after connecting the circuit. @ F The net electric ﬁeld inside the nichrome wire is a maximum immediately after connecting the circuit. T The magnitude of the charge on the plates of the capacitor decreases with time. V @ F The current in the nichrome wire decreases with time. T @l' he electric ﬁeld within the gap between the capacitor plates decreases with time. 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 (25 pts): Two batteries and two wires are connected as shown in the diagram above. The wires are made of the same metal, which has 7e28 mobile electrons per cubic meter. The electron mobility in this metal is 4e—4 (m/s)/(V/m). The top wire has a radius of 0.45 mm, and is 40 cm long. The bottom wire has a radius of 0.20 mm, and is 35 cm long. Each battery has an emf of 1.2 volts. (3: 20 pts) In the steady state, what is the magnitude of the electric ﬁeld inside the top wire? Show all steps in your work. i%-—ETO£ LTOP “Luv/V .— EBOTéﬁaT—ZO ( - ~ " .2 /.2 v) LTD? : L 3°?" ' W :— ,. _ 1 "ATM u gap -; "/4331, at EMT ///;)‘ L Tar , 40" + : <x\ 7T(.206'3)2 A1307 ~ - ﬁr..— ETOP— '2 A [‘70P or (b: 5 pts) How many electrons pergecond leave the negative terminal of the left-hand battery? Show all steps in your work. «45 79? reg 23 w->(n ( . 4563 m}">(‘/e-‘/ /, ?7e [7 C/ectrWIS 5 L : ‘4 AToP m/5 Vm (A Hf) ll ...
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Test3Practice_2007key - Problem 1(6 pts An electron is...

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