Phys4W09MT1230Solutions - Physics 4 Midterm Jan 29 2009...

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Unformatted text preview: Physics 4 Midterm, Jan. 29, 2009. 12:30 PM Name: SQ f! l’l:l*0 mg - Seat: Exam form A Do not begin until instructed to do so. We will not answer any questions during the exam because doing so might unfairly disadvantage those that end up sitting away from the aisles Where they are unable to ask questions. Because of this, I have carefully reviewed the wording of the questions to make them clear. This policy may be a nuisance, but at least it is a fairly applied nuisance. Please do not try to cheat on this exam. It is not likely to help your score, and it is not worth risking a UC degree for one exam. Some potentially useful reminders: fcos (@653: = sin (:13) fsin (15)::52: = — cos (:1?) Ie=mm 1. (8 points) Answer the following true or false questions. 0 (T or® A11 magnetic field lines begin at the N pole of a mag et and end at the S pole. The? chow + ins-am» 0"" can ~ '(T0I®1}X§::2. gxikzgi . @orF)|£xA'[=0. \zes, Fl 1'5 Parallel 42> {ts-L}? c @or F) The lineintegral around any fixed, closed path of the component of the E field tangent tg the path is zero if the magnetic flux is constant in time. S? E ‘32 5 " ‘5 ElaEB/CH: a (T or® The units of EMF are Newtons (N). The. vac-F5 ars— U0 H45. 0 ®or F) A magnetic field can change the velocity but not the Speed, of a charged particle moving in it. 5? {s alum»): par pawl Err—ulcer A . +0 V_. 0 (Der F) Two parallel conductors carrying current in the same direction will attract each other. (a —‘“5 (D rFBI.- 4+ ’2. Fahd-S ”P- i z .J. .. i 0 @or F) The unit_s_ for magnetic field are N/(A - m). P Paints [151+ F 3 IL?» B 2. (2 points) Suppose that a gold ring is lying in the X-y plane and there is a uniform and constant magnetic field directed along the +zraxis. * If the ring undergoes thermal expansion, in what direction will the Effaffwfl Mtg-5 induced current flow?‘lockwise so that )1 points along negative 2". A .&r ”(it (b) counter—clockwise so that {I points along :2. (c) no current will be :g' MOVE “0721;“? induced in the ring. IVthct cur will afross- Hurt. 3. (2 points) Suppose that a conducting ring lies in the X-y plane. If a current flows in the ring in a direction that is clockwise when Viewed . . . . . . A from a pomt on the +2 ans, which directlon does a pomt? d" % 4. (2 points) Considering only the earth’s magnetic field, which is about 00001 T, approximately what is the total magnetic flux through the four walls of this room. fiat—F0 bthQL SDEAJ A :0 5. (4 points) Consider two vectors: A— — f4 3 0) and B: (0,1,0). (a). Compute IA} ”H: J4 +3: 3: 5 .4. (b). Compute B X A. only fl} «ccrmnelmulqr "l1: 8, 50 gm: (0, 103x0’r o 03: FLO 0 "’3 6. (4 points) The figure below shows four arrangements in which long par- allel Wires carry equal currents directly into or out of the page at the corners of identical squares Bank the arrangements according to the magnitude of the net magnetic field at the center of the square greatest first Dvm B vac—HM" filer 2.0.44. 0? Hug—cur wire-S - I a l '2. , z I 2. Q “““ @Q ————— @ e ----- 6 e ————— e i ><a l i #Xi ‘ i 7‘3 ' i R 1 I l w I 3 “L i I “I E I [pg 1 l {\ i ”(a) 3 *(b) 3 ”(6)3 L’ («:03 7. (10 points) Two circular loops of wire, each of radius R, lie flat on a table. The centers of the loops are separated from each other by a distance of BB. As viewed from above, loop 1 is on the right and has a current in the clockwise direction. L00p 2 is on the left and has a current in the counter clockwise direction. (a) Draw a representative set of field lines produced by loop 1. Include enough information in the drawing to make clear what the field looks like. (b) Draw a representative set of force vectors 0n loop 2, enough to make clear that you know the force at all points. In what direction is the net force acting on loop 2. 5i 9- VCLMJ T23?) {Gr-LL) ' ‘ 61.1“ NH’ Fm‘ce- CS hrqurA, loofl Lita—US": «Micro. is A imrj‘u‘ Slang. an “FLU- 9f‘vtce. mam" (Mi) 1 *i’hmvk HM. Offlos'FVLJV CiN‘cLC he! Form. cm a skis- cum—6&7! firm to? 1. 8. (20 points) Prove that the magnetic field is uniform everywhere inside an infinitely long, tightly wound, current—carrying solenoid. You must Show your work and explain each step to get credit. Set-e. /a.¢-i-v‘ra. Mf—as aorta-l “Fax—Hoook. 9. (20 points) As shown in the figure below, a, rectangular loop is near a long wire. The 100p is a distance R from the wire; it has a width of a and a height of b. A current I flows through the wire that varies with time such that [(t) = 3 + ct, with c > 0. Determine the EMF induced in the loop at t z 1 second. In which direction does the induced current LaafiOW? finerwfiv 'Wé- fiat-v; R‘vid Hm. EMF: 99M .1; ”=1 Fawraeiafgi 53...“). g: ”CJQE/‘J‘E‘ I -'TLL1 £405! is ég: §§.JE auburn g: Mal/2m- Foimkad 391% Jim P’“°5e'; ‘07} M; ("r-314% Lame} role... But; 1§I UM‘RS - Account?- Across +51% AN‘M ég a. ifiéfj 50 We. ken-Vi. +0 er ”‘44-. iv: “Us. iu'fhajfaj. DmFi‘mg a Emit. Heat f“?‘” T am Y "" ”A“ A”: A' __A :- (MET-u— (15%: 5‘3“!" " g 211“? ("2‘ k)“: zu‘rdlq' J 4, 3:; r91 3:41 Hm wartime“ 57;st inflow-3 Moi 34" 1‘ P" git: “new 9dr _ '3 Mai- _ __ ‘46:“ : Mot-A %\ QB LSR a??? £1 4* " KP“ “err? (176‘ 2"“ )Le. .. MQIAMR‘rb " 3T 52,, N31”; P‘l’fl M +93“. +10%“ Agfgfiéaswdfl 5'4" :66“):- ETC-'7 (£5: figfil fig? %(3+¢£3. ' .. ~Mo°KC EYE Ma. 4. , Avid E: t: Mfgén .- 3”? L. 25 w “795) The Carnegi— 9's imiucad anachrwdaakmfih £49) (0.5 Wadi-J about) 7% arfgfia. Ma. Engpmsiwfi flux ”4+0 6 +£13- ‘fwflfl. I ...
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