exam1_solns

exam1_solns - Physics 216 -- Exam One February 26, 2011...

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Unformatted text preview: Physics 216 -- Exam One February 26, 2011 Name: Multiple choice (please circle only W): é 1. What are the units of an Electric field? (a) N (b) J (d) J/C (e) both a and d (t) none of these 2. What are the units of Electric Potential? (a) N (b) J (c) (N - m)/C (d) J/C ' (e) both c and d ‘ (f) none of these 3. Consider two solid charged spheres with equal but oppOsite charge. if the spheres are separated by a distance r (so that they are not overlapping), the electric force between them is (a) Attractive and inversely proportional to the square of the distance between them. (b) Repulsive and inversely proportional to the square of the distance between them. i § § 3 § 3 E . § (c) Attractive and linearly proportional to the distance between them. .(d) Repulsive and linearly proportional to the distance between them. (e) Attractive and doesn’t depend on the separation. 4. At the dot, the electric field points (assume all charges are of equal magnitude): (a) Left. (b) Right. Down. (e) The electric field is zero. Physics 216 -- Exam One February 26, 2011 5. A proton is released from rest at Point B, where , the potential is 0 Volts. Afterward the proton __100 V 0 V +100 V s o (a) Remains at rest at B. b Mo - - Awith a constant se d. l l ' - _ _ An B 0 Moves towar :- WI h an mcreasin speed. i { (d) Moves toward C with a constant speed. . (e) Moves toward C with an increasing speed. “,w._mm t V: Co 1 l l 6. Consider the following two-dimensional cross sections through three dimensional closed surfaces. Rank in order from largest to smallest the electric flux through the surfaces A to D. (a) A, B, C, D (b) A, B, D, c (c) B, , A. D (d) B, A, c, D (e) Not enough information to solve. 7. Rank in order, from largest to smallest, the magnitude of the forces a proton would experience if placed at each of the points (a through e) inside this perfect parallel-plate capacitor. (A) a and b same, then c, then d and e same (B) d and e same, then c, then a and b same (C) b, a, c, d, e (D a, b and 0 same d, e (E) All points are equivalent 2.0 20 Physics 216 -- Exam One February 26, 2011 Instructions: 1. Do all of your work on these pages. 2. If you need more space, you may use the back of the page or additional sheets of paper but clearly indicate the number of the problem. 3. Show all of your steps in problems for full credit. 4. Be clear and neat in your work. Any illegible work, or scribbling in the margins, will not be graded. 5. Please draw a box around your final answers. Problems: 1. State Gauss’ Law and explain what it means physically. §=§Eoofi= 9% O The "moi —\\Aroo$\,\ a. Gauss} an Sur—cace ewc\cs\n(j a CMargg d‘tskr‘tloo’rlon ls propor¥;omo§ *0 JAN; shared; e-AC\05QO\ . 2. Consider a hollow neutral conguggr which contains a positive point charge of charge q=+6: Physics 216 -- Exam One February 26, 2011 a. Sketch the distribution of charge for the conductor (on the figure). b. What is the total charge on the inner surface of the conductor? [E c. What is the total charge on the outer surface? d. What is the electric field far outside the conductor? “4%? " "mw " " / be 3. Two infinite lines of charge, each with linear charge density l , lie along the x- and y- 20 axes, crossing at the origin. What is the electric field strength at position (x,y)? FHAA- s’vux \‘V Physics 216 -- Exam One February 26, 2011 Z o 4. Consider a 2.0 cm by 2.0 cm parallel plate capacitor with a 2.0 mm spacing which is charged to 1.0 nC (pictured below). First a proton and then an electron are released from rest at the midpoint of the capacitor (ignore the effect of the particles on each other). 15* 2‘1 \A 5‘ Q3“ Wm: Wildcat: "mm;me r‘ "Ram;uBM-‘wammwmwlwWimmmpflflmflm‘Wmuwwmwammmxfiwmmmmwmmmnwmr. ‘ M,w«~m«,r t , a. What is each particle’s change in electric potential energy from its release until it collides with one of the plates? 3&ka *raN-A 5: (“1, fl AKA WoJ‘K Pr°*°aa Au: U“? “u; = (“0*0‘) “ (210+ get-’3‘»: — é: QEC)‘ §n Alrufi'hn c-Q- Q2010, ¢ '- - '2 ' __ "A ...-L e,\e.c\ro~n. AU-Ugg u. “0+(QAEA ~— Up-tpdfiz " 2Q AU‘C — 3.. _ §N E- "A," e.A-2-“1*‘0 ‘5 U -i" A“ 7- ‘ LLS‘L-‘O T (5W ’Cor EMMA) b. What is each particle’s speed as it reaches the plate? FDo‘HA (LMSLA “perm.” rest KE; :0 Kg: smut = ME: '!.\\A Thu"), : “lrbnu‘ massas o3 parMchS qu, {rh— vafl‘j fl‘uuruuxca, FM‘ 5 ) ligVfi’gf‘ SQ ‘90-ng Agfiaggévgqfiéfiw ...
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exam1_solns - Physics 216 -- Exam One February 26, 2011...

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