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# exam2_sol - Physics 2020—002 Name: KEY Exam 2A — 1...

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Unformatted text preview: Physics 2020—002 Name: KEY Exam 2A — 1 March 2010 Part A: Hard Multiple Choice (10 points total, 2 points each, Circle Best Answer). 1. A proton moves directly into the page away from you and an accompanying magnetic ﬁeld points to the bottom of the page. What direction does the magnetic force point? a) cut of the page toward the left 0) into the page d) toward the right e) toward the page top 2. Fully charged capacitor in an RC circuit is allowed to discharge. If the capacitor reaches one— quarter charge in 4.24 8, what is the time constant of this circuit? /L;__ t L “(.3842 a) 12.4 s b) 8.88 s @965 s d) 4.24 s e) 0.555 s .3 59,244 —’t/R<; -t//¢, -t/ﬁ’ ‘6 3(9 = e :Qe 3 ,_ i -—‘-= i: i __ 3. A 342 m long wire carrying a current of 2.88 A is embedded in a 23.9 mT magnetic ﬁeld such that it experiences a maximum force from the magnetic ﬁeld. What is the magnitude of this maximum force? a) 3.29 N b) 68.8 N c) 4.97 N d) 985 N @35 N 5281424849 = 9:9 : (23.9-x/o“573(2884\ (541% 4 .288 [J 4. A battery has an emf of 2.40 V. If this battery produces a voltage of 2.22 V when a current of 0.122 A is being drawn from it, what is the internal resistance of this battery? a) 19.7 9 “ b) 0.122 9 c) 2.40 9V d) 18.2 o @48 n — *_ = - \/ :5m ,9.4ov-a.21 AV’E :V\ TV- 8 A) ll\ I 5. A current of 2.88 A is ﬂowing through a straight Wire. What is the strength of the magnetic ﬁeld at a distance of 50.0 cm from the wire? a) 15.3 mT b) 24.0; c) .15 MT\ d) 3.20 mT e) 30.5 mT . I 477 b * — 15— ’u” : ( W0 [AM/A30 33% : [.15’x /o 97‘ : /,/5’I“7“ PHYS-2020-002: General Physics II — Exam 2A — 1 March 2010 Page 2 Part B: Easy Multiple Choice (10 points total, 1 point each, Circle Best Answer). 6. Why should a third “grounding” Wire be used in the power cords of all electric devices? a) In order to ensure the polarity of the plug. b To allow negative voltages to be “realized” by the device. ) c) To supply the electrons for the device. N d) o prevent a short circuit. e) To increase the proﬁts of electric companies. 7. A coiled Wire carrying current is called a a) spectrograph @enoid c) magnetometer d) galvanometer e) seismograph 8. Counting the number of ﬁeld lines that cross a surface area is called the a) inductance b) polarity @ux d) motional emf e) induced emf 9. Which characteristic of the Earth lead to the discovery of the ﬂipping of the Earth’s magnetic ﬁeld? a) length of clay b) length of year c) axis precession @ontinental drift e) compass drift 10. Whereas Kirchhoif’s junction rule is the conservation of charge, his loop rule is conservation of a) force b) ergy c) momentum d) mass e) none of these PHYS-2020-002: General Physics II — Exam 2A — 1 March 2010 11. Which of the following equations is the basis behind the operation of audio speakers? @=Bresin6 a) P = ka/(MmH) b) E = mc2 d)FAt=Ap e) 8=NBAwsinwt 12. The ﬁrst hint of the existence of magnetism came from the discovery of @oadstones e) limestones a) basalt rocks 0) meteorites cl) lightning 13. Who discovered the phenomenon of self—induction? a) Franklin b) Lenz @{enry d) Oersted e) Coulomb 14. The SI unit for magnetic ﬁeld ﬂux is called the a) volt b) ohm c) ampere @nmber e) tesla Page 3 15. When the sum of spins of electrons contained in matter add up to a non—zero value, such material is called a) ohmic @rromagnetic c) ampic d) voltic e) neutral PHYS-2020-002: General Physics II — Exam 2A — 1 March 2010 Page 4 Part C: Problems (20 points total, 10 points each). 16. The circuit in this diagram has a 24.0 V battery and three resistors With R1 = 32.0 S2, R2 = 24.0 9, and R3 = 48.0 D. Calculate the equivalent resistance of this circuit. (Don’t forget to Show your diagram for each step.) (b) What is the current ﬂowing though R1? (0) What is the potential drop across R3? (Show all work!!!) PHYS-2020-002: General Physics II — Exam 2A — 1 March 2010 Page 5 17. A 15.2 MeV cosmic ray positively charged ion has a mass of 3.45 X 1026 kg moves in a circular orbit Whose orbital plane is perpendicular to a uniform 2.88 X 10“8 T magnetic ﬁeld. (a) If the radius of this circular orbit is 9890 km, What is the charge on this cosmic ray ion? (13) Approximately how many electrons would this ion be deﬁcit, that is how many extra electrons would this ion need to make it a neutral particle? (Show all work!!!) “ . —!C!__ é a .6: 2- -11, 03KE*/521Me\/7<_’ D 5’0 ‘5 X4231 : 9,43x/o o lev [Me\/ i 2. 3K5 m E : 47 :_ 2 . l 7 2: cl ID ’15" / C/ x A _ M’U‘ MW" r, x 70m -—- \$8 ) {‘3 7.6; t - _ 7 , A8 75:: (Mex/o l [alcrx/D m/a : [044MB C (9:370 x m" (2,83 2< walla ’ A 98 --—> WW Wg’w‘e ﬁﬂg Wﬁwgejﬁmmmﬂ. PH YS—2020-002: General Physics II — Exam 2A — 1 March 2010 Page 6 Extra Credit Problem (5 points, do this only if you have time). 18. Assume that a lightning bolt can be represented a by long straight line of current. If 22.0 C of charge passes by in a time of 2.00 X 10“3 seconds, What is the magnitude of the magnetic ﬁeld at a distance of 50.0 meters from the bolt? (Show all work!) ...
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## This note was uploaded on 03/21/2012 for the course PHY 2020 taught by Professor Staff during the Fall '08 term at University of Florida.

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exam2_sol - Physics 2020—002 Name: KEY Exam 2A — 1...

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