Plan o o. I(t) Divide problem into sub-problems Modify schematic and coordinate system (if needed) Write general equations

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1 STAPLE Physics 201 Name Final Exam May 14, 2013 This is a clsed bk examinatin but during the exam yu may refer t a 5 x7 nte card with wrds f wisdm yu have written n it. There is extra scratch paper available. Yur explanatin is wrth ¾ f the pints. Explain yur answers! A general reminder abut prblem slving: Shw all yur wrk. Really; Shw All Wrk! Fcus Physics Draw a picture f the prblem What is the questin? What d yu want t knw? List knwn and unknwn quantities List assumptins Determine apprach What physics principles will yu use? Pick a crdinate system Simplify picture t a schematic (if needed) Plan Execute Evaluate Divide prblem int sub-prblems Mdify schematic and crdinate system (if needed) Write general equatins Write equatins with variables D yu have sufficient equatins t determine yur unknwns? Simplify and slve Check units Why is answer reasnable? Check limiting cases! 1. [4 PTS] Yu cnnect a resistr (222 Ω) and capacitr (500 µμf) in series with a battery (1.5 Vlts). What is the time cnstant? a)! = 0.009! b)! = 0.111! c)! = 0.150! d)! = 9.01! e)! = 111! 2. [4 PTS] A clsed lp is placed next t a wire (see belw). The wire carries a steady DC current f I=50 ma. The lp des nt mve relative t the wire. a) There will be n induced current. b) There will nly be an induced current if the lp mves parallel t the wire. c) There will nly be an induced current if the lp is rtated 90 s its surface nrmal vectr is parallel t the wire. d) There is a cnstant induced current. e) There is an scillating induced current. f) Nne f the abve I(t)

2 3. [4 PTS] A generatr with an effective (rms) vltage f 24 V AC is cnnected t a transfrmer n a side with 100 windings. The ther side has 1500 windings. What is the effective (rms) utput vltage? a) 360 V b) 36 V c) 16 V d) 1.6 V e) 0 V 4. [4 PTS] A prtn mving in the +x directin enters a regin f unifrm magnetic field that is als riented in the +x directin. In which directin des the prtn feel a frce? a) The +y directin. b) The +z directin. c) The -y directin. d) The -z directin. e) There is n frce. 5. [4 PTS] A resistr (! = 3.0 Ω) is placed in series with a real battery (V emf = 8.8 Vlts) and yu measure a current f 2.75 A. What is the current in this circuit if yu replace the resistr with a! = 5.0 Ω resistr? a)! = 4.58! b)! = 1.76! c)! = 1.69! d)! = 1.65! e)! = 1.06! 2

3 Physics [4 PTS] A charged bject,! = 25!", is mving thrugh a regin f space with a cnstant magnetic field,! = 0, 0, 0.45!. When the bject is at! = 2, 1, 2!, it has a velcity! = 4 10!, 0, 0!/!. Assume the bject is nnrelativistic,! = 1. What is the frce n the bject? a)! = 0, 4.5, 0 m! b)! = 0, 4.5, 0 m! c)! = 0, 0, 0! d)! = 4.5, 2.25, 0 m! e)! = 4.5, 2.25, 0 m! 7. [4 PTS] A lng wire psitined alng the x-axis has a current f! =< 1.2, 0, 0 >! flwing thrugh it. Yu measure the magnitude f the magnetic field 2 cm frm the center f the wire. Yu mve s yu are nw 8 cm away. What happens t the magnitude f the magnetic field at yur new bservatin pint? a) Increases by a factr f 4 b) Increases by a factr f 2 c) Des nt change d) Decreases by a factr f 2 e) Decreases by a factr f 4 f) Nne f the abve 8. [4 PTS] Yu cnnect three identical capacitrs (! = 3!") in parallel. What is the value f the effective (r ttal circuit) capacitance? a)! = 9!" b)! = 6!" c)! = 1!" d)! =!!!" e)! =!!!" 9. [4 PTS] A hllw metal cube is placed 2 cm frm the center f a 5 C charged bject. The bject and cube are in static equilibrium (neither is mving). What is the vltage inside the hllw metal cube? a) The vltage is zer. b) The vltage is largest n the side clsest t the charged bject. c) The vltage is cnstant inside the cube. d) The vltage is largest n the side furthest away frm the charged bject. e) There is n vltage inside the cube. 3

4 10. [4 PTS] A charged particle (q = 35 µc), is mving with a cnstant speed alng the x-axis,! =< 8 10!, 0, 0 > m/s. When the particle is just passing the rigin,!! =< 0, 0, 0 > m, what is the magnitude f the magnetic field at!! =< 5, 0, 0 > cm? a)! = 112 mt b)! = 5.6 mt c)! = mt d)! = 5.60 µμt e)! = 0 T 11. [4 PTS] Tw small charged spheres are lcated in an empty regin f space. Sphere ne has twice the charge n it than sphere tw (!! = 2!! ). The magnitude f the frce n sphere ne is 12 N when the center-t-center separatin f the spheres is 1.2 meter. What is the magnitude f frce n the sphere tw when the spheres are 0.6 meters apart? a) 3 N b) 6 N c) 12 N d) 24 N e) 48 N 12. [4 PTS] A large neutral metal sphere is grunded thrugh a switch. A psitively charged balln is brught near it (but des nt tuch it) while the switch is clsed. The switch is pened (the sphere is n lnger grunded) and the balln is taken away. The sphere is nw a) charged but we cannt knw its plarity. b) neutral (has n net charge). c) negatively charged. d) psitively charged. e) nne f these. 13. [4 PTS] An electrn is placed exactly in the middle between tw parallel plates. One plate is held at 50V while the ther is held at -50V. Circle every crrect statement. a) The electrn mves tward the 50V plate. b) The electrn mves with cnstant velcity. c) The electrn mves tward the -50V plate. d) The electrn des nt mve since it is at 0V. e) The electrn mves in a circle due t the right hand rule. f) The electrn mves with cnstant acceleratin. 4

5 The next tw prblems cncern a duble cnvex plastic (n=1.2) lens yu are using n the beach. 14. [4 PTS] Yu are using this lens as a magnifying lens. Circle every crrect statement. a) The lens has a fcal length less than zer. b) The lens has a fcal length greater than zer. c) A real, magnified image is prduced if!! > 2! d) A real, magnified image is prduced if 2! >!! >! e) A virtual, magnified image is prduced if!! <! f) A virtual, magnified image is prduced if!! >! 15. [4 PTS] Yu decide t take the lens yu were using abve and use it under water (n=1.33) t magnify the pretty cral and shells yu are interested in while scuba diving. a) This wrks fr any bject distance. b) This des nt wrk fr any bject distance. c) This wrks s lng as the bject is clser than the fcal distance. d) This wrks s lng as the bject is further than the fcal distance. The prblem can be dne using a prblem slving sheet r n additinal paper. Fllw the prblem slving guidelines. 16. [12 PT] Yu are visiting yur Aunt Peg when yu ntice that she is hlding her reading glasses 10 cm frm her eyes t read a bk placed 45 cm in frnt f her eyes. Yu knw she shuld have her reading glasses (D=+2.5 m -1 ) resting n her nse 2 cm in frnt f her eyes when she is reading her bk 25 cm in frnt f her eyes. She tells yu nt t bther but yu want t get her new glasses. The prblem is she wn t g t the stre with yu s yu have t determine the crrect prescriptin. Gd thing yu tk physics! What is her new prescriptin?!!!! = 10!!!!!!!!!! =! = 9 10!!!!!!!!"!!"! =!!!!! and!!"!!"! = 4!!! mass f electrn!! = !!"!" mass f prtn!! = !!"!" charge f electrn!! = !!"! charge f prtn!! = !!"! charge f neutrn!! = 0! mass f neutrn!! = !!"!" 5