Physics o"
240 Exam Second
March 912000
Your printedname Your Signature Instructions: long. Theexamis 75 minutes check youhaveall pages. Therearc20 questions, that No or and You mayuseone3" by 5" cardof notes a calculator. othernotes booksare are text PC's,PDA's,or calculators extensive displays not with allowed.Notebook allowed.
Make sure you correctly copy your choicesto the answer sheet. Make sure you put the examversion (3) and your sectionon the answer sheet.
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Section 004 005 006 014 015 016 018 022 023 024 025 026
Time 11 12 1 2 3 4 8 9 10 11 1 t2
Instructor Merlin Merlin Bretz Bretz Brctz Yokoyama Yokoyama Yokoyama Roe Roe Merlin Roe
Room 224Dennison 224Dennison 224Dennison 222WestHall 222WestHaIl 222WestHall 216Dennison 216Dennison 216Dennison 414Dennison 22l Dennison 221Dennison
Prefixes:Mmega=106,kkilo=103,mmilli=10-3,pmicro=10-6,nnano=10-e,ppico=lg-12 Useful constants: Coulomb'slaw constant Chargeon electron Mass of electron Mass of proton Perririttivity of free space Permeability of free space Speedof light in vacuum k = 8.988* 10n N-m'/C' -I.6 * 10-t' e= C me= 9.11x 10-31 kg * 10-21 mp= 1.67 kg = 8.85 * 16-t2 so C2A.{-m2 * 10-7 T-m/A IIo= 4n m/s c = 3.00 x 108
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Physics 240Exam2 1. A battery is used to chargea seriescombinationof two identical capacitors. ff the potential difference acrossthe battery terminalsis V and total chargeQ flows through the battery during the charging processthen: A) B) C) D) E) the chargeon eachcapacitoris Q and the potential difference acrosseachcapacitor is 2V the chargeon eachcapacitoris Q and the potential difference acrosseach capacitor is V the chargeon eachcapacitoris Q and the potential differenceacrosseach capacitor is V/2 the chargeon eachcapacitoris Q/2 and the potential difference acrosseach capacitoris V the chargeon eachcapacitoris Q/2 and the potential difference acrosseach capacitor is V/2
2. Suppose one has available: two sheets copper of = a sheetof mica (thickness 0.1 mm, r = 6) a sheetof glass (thickness= 2 fi:rrr^, = 7) r = a slab of paraffin (thickness 1 cm, r= 2) placebetweenthe two copper sheets: To obtain the largestcapacitance, A) B) C) D) E) a 1 mm gap of air the mica the glass the paraffin the mica, glass,and paraffin
3. A cylindrical copper rod has resistance The rod is reformed to twice its original length with no R. changeof volume.The new rod'sresistance is:
A)R B) 2R c) 4R D) 8R E) R/2
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240Exam2 Physics 4. For an ohmic substance resistivity is the proportionality constantfor: the A) B) C) D) E) current and potential difference current and electric field current density and potential difference current density and electric field potential difference and electric field
5. An electric power plant delivers 10,000kW of electric power over a long distanceto a city. It is better to sendthe the 10,000kW at 10,000V rather than at 220V because: A) B) C) D) E) thereis lessheatingin the transmission wires the resistance the wires is lessat high voltages of more current is transmittedat high voltages the insulation is more effective at high voltages the "iR" drop along the wires is greaterat high voltage
6. An ordinary light bulbis marked watt,120volt".Thebulb's(heated) "60 resistance is: A) B) c) D) 60A 120Q 180Q 240A
E) lss,
7. A battery is connectedacrossa parallel combination of two identical resistors. If the potential difference acrossthe terminals is V and the currentin the battery is i, then: A) B) C) D) E) the potential differenceacrosseachresistoris V and the current in eachresistoris i/2 the potential difference acrosseachresistoris V and the current in eachresistor is i the potential difference acrosseachresistor isYl2 and the current in eachresistor is i/2 the potential difference acrosseachresistor isY/2 and the current in eachresistor is i none of the aboveare true
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Physics 240Exan2
8. A totalresistance 3.0 Q is to be produced combining unknownresistorR with a L2e of by an resistor. Whatis thevalueof R andhowis it to beconnected the 12O resistor? to A) B) C) D) E) 4.0S),parallel 4.0Sl, series 2.4C),parallel 2.4S),series 9.0C),series
9. Two 110-Vlight bulbs,one"25 W" andtheother"100W", areconnected series a 110V in to source. Then: A) B) C) D) E) the 25W bulb will thecurrentin bebrighter the 100W bulb is lessthanthatin the25W bulb the voltagedropacross both bulbswill bethe same rhe 100w bulb will bebrighter thecurrentin the 100w bulb is greater thanthatin the25 w bulb
10. A certain capacitor, series a 720Slresistor, being in with is charged. theendof 10msthe At capacitor's charge halfthefinalvalue. capacitance is The is about: A) B) C) D) E) 9.6uF 14riP 20pF 7.2F 10F
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Physics Exam 240 2 11. A uniform magneticfield is directedinto the page.A chargedparticle, moving in the plane of the page,follows a clockwise spiral of decreasing radius as shown. A reasonableexplanationis: a & a
6
A
@
-+ B 6
A) B) C) D) E)
the charge positiveandslowingdown is the charge positiveandspeeding is up thecharge negative speeding is and up the charge negative slowingdown is and noneof the above
12. An electron enters regionof uniformperpendicular andB fields.It is observed the a E that velocityv of the electron unaffected. possible is A explanation is: A) B) C) D) E) v is parallelto E andhasmagnitude E/B v is parallelto B v is perpendicular bothE andB andhasmagnitude to BIE v is perpendicular bothE andB andhasmagnitude to E/B thegivensituation impossible is
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Physics 240Bxam2 13. The current is from left to right in the conductor shown.The magneticfield is into the pageand point S is at a higher potential than point T. The chargecarriersare:
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T
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A) posrtrve B) negative
c) neutral
D) absent E) movingnearthe speed light of
t4. A square loop of wire lies in theplaneof thepageandcarries currentI asshown.Thereis a a uniformmagnetic field B parallelto thesideMK asindicated, directed towardthe top of the page. The loop will tendto rotate:
A) B) C) D) E)
aboutPQ with KL comingout of thepage aboutPQ with KL goinginto thepage aboutRS with MK comingout of thepage aboutRS with MK goinginto thepage aboutan axisperpendicular thepage to
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Physics 240ExamZ 15. Two long straight wires are parallel and carry current in the samedirection. The currentsin the wires are 8.0 A and 12 A and the wires are separated 0.40 cm. The magnitude of the magnetic by point midway betweenthe wires is: field in tesla at a
A) 0 B) 4.0x10-a D) 1.2xL0'a E) 20x1.0-a
c) 8.0x10-a
16. Fourlong straightwirescarryequalcunents into thepageasshown. The magnetic forceexerted on wire F is:
n
s
a *-l-' I
a s
N
a
A) B) C) D) E) north east south west zero
17, Solenoid hastwicetheradiusandsix timesthenumberof turnsper unit lengthassolenoid 2 1. Theratio of the magnetic field in theinteriorof solenoid to thatin theinterior of solenoid1 is: 2
A) 2 B) u6
c) 6
D) 1 E) U3
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240Exarn2 Physics 18. A long straight wire carrying a 3.0 A currententersa room through a window 1.5 m high and 1.0 m wide. The path integral Jn .ar aroundthe window frame has the value (in T.m):
A) 2.5x10-7 B) 0.20
c) 3.8x10-6
D) 3.0x10-7 E) noneof these
flux throughit field andthemagnetic this to L9. Suppose pageis perpendicular a uniformmagnetic an is 5 Wb. If the pageis turnedby 30' around edgetheflux throughthepagewill be: A) 2.5Wb B) 4.3Wb
c) swb
D) 5.8wb E) 10Wb
loop.The straightwire carries a conducting 20. A long straightwire is in the planeof a rectangular the While thewire is beingmovedtowardtherectangle currentin currenti, asshown. constant is: the rectangle
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A) B) C) D) E) zero clockwise counterclockwise in in elockwise the left sideandcounterclockwise theright side in in counterclockwise the left sideandclockwise theright side
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v,fuvgan) Physics 240Exam2
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Answer Key -- 240Winter 00 Exam 2 1. C 2. B 3. C 4. D 5. A 6. D 7. A 8. A 9. A 10. C 11. D 12. D 13. A 14. A 15. B L6. B on thecharge eachcapacitor Q andthepotential is difference across eachcapacitor V/2 is themica 4R cuffentdensityandelectricfield thereis lessheating the transmission in wires 240A thepotential difference across each resistor V andthe currentin eachresistoris i/2 is parallel 4.0 SJ, the25 W bulb will be brighter 20 U.r' thecharge negative slowing is and down v is perpendicular bothE andB andhasmagnitude to E/B positive aboutPQ with KL comingout of thepage 4.0xL0-a east
t7. c
18. C 19. B 20. C
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3.8x10-6 4.3Wb counterclockwise
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