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Unformatted text preview: 6*.“ 10. 11. 12. Physics 227 — Hourly Exam 2 Thursday, November 18, 2010, 9:40 PM — 11:00 PM
ARC—103 (A—K), PILL—114 (L—R) and SEC—111 (SZ) Your name sticker SOLUTWMS
Q’X Use a #2 pencil to make entries on the answer sheet. Enter the following
id information now, before the exam starts. In the section labelled NAME (Last, First, MI.) enter your last
name, then ﬁll in the empty circle for a blank, then enter your
ﬁrst name, another blank, and ﬁnally your middle initial. Under STUDENT # enter your 9—digit RUID Number. Under CODE enter the exam code given above. Enter 227 under COURSE. You do not need to write anything else on the
answer sheet for now, but you may continue to read the instructions.
During the exam, you may use a calculator and are allowed one 8.5 x 11
inch sheet of paper with whatever you want written on it. For each of the 16 multiple choice question mark only one answer on the
answer sheet. There is no deduction of points for an incorrect answer, so if
you cannot work out the answer, you should make an educated guess. If you have questions or problems during the exam, raise your hand and a
proctor will assist you. We will provide values of physical constants that
are needed but not given, but we will not provide equations. A proctor will check your name sticker and your student ID sometime during
the exam. Please have them ready. You are not allowed to give help to any other student, ask for help from any
one but a proctor, or change your seat without permission from a proctor.
Doing so will result in a zero score for the exam. When you are done with the exam, hand in only this cover sheet and your answer sheet.
Please sign above by the name sticker to indicate that you have read and understood these instructions. Possibly useful constant: 60 = 8.85 x 10’12 C2/Nm2, k :2 1/47reo = 8.99
X 109 Nm2/C2, c 2 speed of light = 3.00 x 108 m/s, ~qelecmn = qpmton
= 1.602 X 10“19 C, melecmn == electron mass = 9.11 X 10‘31 kg, mpmton 2:
proton mass = 1.67 X 10’27 kg, no 2 4n X 10‘7 Tm = 12.57 X 10“7 Tm, and 1 eV :2 1.602 X 10‘19 J. :> with exam code uh‘aliﬁko A thin copper Wire of 0.20 mm diameter carries a current of 2 A. Copper has
8.4 X 1028 free electrons per m3. What is the drift speed of the electrons? a 6.06 x 103 m sec .. ‘ elm Aha“)! wows)
bl 2.1 x 106 m/éec I (A) ' $11611.) “:1 t 3) v
_..... .. . ,. c) 6.11x10‘41n/sec U. _‘ z
‘9" gNA " Ll,LHO'W)C3.‘Q¥IDL5)CEGym.“) e 1.48><10 m/sec
= uJHO'BMLS A cylindrical copper Wire (resistivity = 1.70 x 10’“8 Q  m) With a diameter
of 1 x 10"3 m and 0.01 m long is used to connect two points on a printed
circuit board at room temperature. If the current in the Wire is 10 mA, What is the potential drop across the Wire? a) 0.54/1V V=IR R: A“
am; ~ "2‘
3; 3:61am V: 11A: 1: (Wig—91):; renew
. m 2 ‘
e) 5.4 mV A EU”) A battery has an emf, 5, and an internal resistance, 7". When a 59 resistor
is connected across the battery, a current of 2A ﬂows. When an 119 resistor
is connected, 1A ﬂows. The internal resistance of the battery is: @ 2:2(1’4’53 azicrﬂq C) 59 ZPﬁ‘D: P4'l‘
(1)100 r; {LIL
e) 79 Consider the circuit in the ﬁgure, With 24.0 V across the network of three
identical resistors each With R 2 16.0 9. What is the reading of an ammeter
With resistance 3.00 Q, When it is inserted at point a at the right end of the 3 resistors? a) 0.75 A
1.0 A 
::X__ at“)... R ‘7‘" +l$
R Quay“ “1" {2+1};
= 0.8‘IA = 8*“ 5. In the circuit shown, the current ﬂowing through the 0.5 Q resistance is
0.80 $2 1.2 Q :1 U a) 4.0A 5"“ “EHQU‘J‘L‘ 8v 3%
5mm upH—asg ' “UL
c; 0.8A 0"" “‘2— .512. r2554» . . . I d) 38A “We 2J2. abbwalw . _ ' {L
8) 80A Vcsfslor, wfw HA hawk 3v, 2A
60 rune/vb C: 3
.51 '5' 2 H“: ~
2.53:: 2. =5 :=~3.2A —> 11qu 6. A resistor dissipates 0.50 W when when the potential drop across it is 3.0 V.
When the potential drop across it is 1.0 V, the same: resistor will dissipate: a) 0.5OW ? __ Vi: 12.11:“th
b) 0.17 W . f" .i , 
c) 1.5 W .1) R 3311/? = 31/95 :‘ ‘83,?" Pa: V'Ll‘z.‘ ‘AB‘z‘Ds'gw e none of these 7. A 1 MP capacitor is charged up to a voltage of 100V. The capacitor is
discharged through a 10 S2 resistor. What is the current ﬂowing after 30 microseconds? _ 71:11;
am 3: “I08,
3) 23A to >VIR' = \UOV/lpaL'J—(OA
. _‘_ I _
d? 0.05AA I 2 WA ( E”... 30W) /\° 5') — 0.57%
e 9.5 g 8. An electron and a proton in the same uniform magnetic field trace out
circles of the same radius, one clockwise and the other counterclockwise. What is the ratio of electron to proton momentum? P:‘Q&L’:f~ c) (5.4 x 104) ‘53 ‘5 B
d) It depends on the radius of the circle.
e) It depends on the magnetic field. P ,. 6 Br 9. Which of the following statements is false? a) The magnetic force does zero work on a charged particle moving in a magnetic ﬁeld.
b) A current—carrying closed loop of wire in a constant, uniform mag—
netic ﬁel 'c force on it. lg A charge moving through a magnetic ﬁeld always fee s a nonzero
magaa am“ force.
*0 (rm By The magnetic torque on a current—carrying coil of wire is zero when
‘ . the magnetic ﬁeld is perpendicular to the plane of the coil.
“4“; ~ e) The net magnetic flux through any closed surface is zero. 10. A wire of length d = 0.5 m lies along the x axis and carries a current I =
2.0 A in the +9: direction. The magnetic ﬁeld in this region is uniform and
in the my plane. The resulting force on the wire is 1.0 X 10“2 2 N. Which
of the following must be true? a) Nothing further about the 1? ﬁeld can be determined. we.
b)' By=~0.005T '6' a. 3; 5i {é Marsh ‘1“, ,Je .D‘.
c) By=0.005T « A .a mag?‘ Ar. 63%,,“
d) By=0.01T mat: x )c B \> m 3 , y = 0.01 cmwﬁ WWW
“ cm paws—yd"
11. A circular coil of radius 40.0 cm with 20 turns lies in the x~y plane in B Z :: D uniform magnetic ﬁeld of magnitude 0.5 T in the +9: direction. The current
in the loop is 6.0 A (in the direction shown in the ﬁgure). The magnitude
and direction of the torque vector acting on the coil is y a) 1.5 Nm in the +2 direction
b) 30 Nm in the —z direction
c) 1.5 Nm in the +y direction a I m in the —y directio ) e none 0 t e others The z—axis is coming
out of the page. 12. Two long straight current—carrying parallel wires cross the 1: axis and carry
currents l and 31 in the same direction, as shown. At what value of a: is the net magnetic ﬁeld zero? a 0 BS—oekﬁs Cube. “1 bp‘ﬂbﬁk b) 2 chlneL'wa5, AdeZ cam X
dc) 10 (RM +9 01 e) 13 w\w§s‘u5\n5 8: ﬁ ‘gz kJ. 4"" x: 13. A long solenoid of 400 turns of wire is 15 cm in length. It carries a current.
of 4.0 A, and is ﬁlled with silicon steel (K = 5200). What is the magnetic ﬁeld inside the solenoid at its center? a) About 2.0 mT B _. K “a H I b About 13. mT _ '122
c; About 20. T “SW—0°“ “"7"” ﬂ>( us) Go e About 10. T 14. In the ﬁgure shown, a conductor consisting of a circular arc of 45° with
radius R and two wires attached to this arc going radially outward (and
effectively inﬁnite in length) has a current I passing through it. What is
the magnitude of the magnetic ﬁeld at point P, the center of the arc? 3») (Mo D/(ZR) b) (#0 0/033) c) 0
W
' MO I (47rR) The, radial ‘65; £9 140+
Mgbula'b msacﬂ a'f' P. (I? Evatwykuiw 00mg,
{0 ix; :0.) (Alglduwr— 1/?
bit—aloof, rm .mfw C(91)“ \90? WNW 31m: Milan, $0 15. A cylindrical wire of cross sectional radius R = 0.0010 in carries a total
current I = 20 A, which is uniformly distributed inside the wire. At a
distance 7" = 0.00050 m from the center of the wire, inside the wire, what is the magnetic ﬁeld strength? B :_ MOI“; ~ Ma y I x "72.) w .a) 0.0020 T :2 Wm 21”. "T 12‘ b .00064T 4) ‘ “a
0) 0.00401“ 9:. 41231. .,. _, (“WHO (20) ENG d) 0.0080T “'3’ 7"" Uh“)
e) The magnetic ﬁeld strength inside the wire is 0 T. B 2* urgr. 16. Two long parallel conductors are separated by a distance of 0.05 m. One of
them carries current of 6.0 A and the other 7.0 in the opposite direction.
The force per unit length the ﬁrst wire exerts on the second is: a) (1.7 x 10—4) N/m; attractive F \_ M“ I I\
b) (3.4 x 10“4 N In; attractive \ le T 2""
. m; repu s1ve _
d) (3.4 x 10‘4) N/m; repulsive 2&1?le '1) LL30” e) none of the above (:5. “0.2)
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 Fall '11
 RonaldGilman
 Physics, Electron, Magnetism, Magnetic Field

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