This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Physics 241
' Fall 2009
Exam 2 November 10, 2009 Giving information to or receiving information from another person while taking this exam is
cheating. To intentionally do anything that would cause the level of your knowledge of the
material to be misrepresented is cheating. Anyone found to be cheating will receive an F for
the course and their names will be forwarded to the Dean of Students. Sign Name 7 Student ID If during the exam you feel there is an equation that should be on the equation sheet contact one of
the exam proctors. Your request will be considered and placed before all the students, if your
request is deemed acceptable. If you feel any of the questions are ambiguous or unclear, complete the problems according to your
interpretation of the problem. Include all your work and calculations clearly. Turn in the paper
version of the exam along with your optical scan sheet. This will allow you to argue your case, if
your solution does not agree with that given as the answer. VERSION 1 Physics 241, Exam 1 Equation Sheet
1 ' 2
k = 9109 NC": I: = 47:12 so = 9.10"12 NC 2 1eV = 14510491 e =1.610“9C .
_ m F=k—1qii= E=ki£ E(p)=ZE,.p dE;k%§Lf 5:1 Ah? 7' 7' £0
_ 4 Q ” _ .. a  a a
¢=jEadA gSEﬁdA=8— AV=‘V,,1{,=—JEdl dU=—Fdl F=qE
S S 0 a
dv=d—U=—Edf VJ? V=2ﬂ Ex=—d—V E =31; 135—91
go ‘ r 1;. dx y dy dz
a AV kdq Q s A Qd 1Q2 1 1
:—_—.— V: ”—— C:— C: a V: U:——=—— V:
E AF r V ' d 29A 2 c 29 2
1 z   _ L _
u=—£oE 8=K£a E=—VV R—P— P=1V a (P Paﬂpo
A
T 4'3
j'cosw) d9 = sin(9) J' sin(9)d9 = — cos(9) jsin2(9)de = g — 5mm) jcos2(9)d9
_d_r_ 1 dr r2 2 —— —=zn(r) jrd9=re jdr=r Ink=3 T r T F=qiixf3 dF=Ide§ Smface (if E ' d7 = #91 Enciosed Loop lelzNZIZ
Kn=ma' V = N d¢tum
d: P=I V rms rms P=—I V 2 mm max
1G =10_4T
#0 = 417x104 Tm/A 1Wb=1Tm2 3' Question 1. xﬁxxkxi
~wxmxmxm 3
I
3
I
I Y waxMxi
ﬁj'gxmxmxm o 1. 2L éL All. 5L ﬁt.
A coil of wire with an area 0sz m2, enters a region of with magnetic ﬁeld, 5—Tesla pointing
into the page. The right edge of the coil of wire starts at 0 as shown. Which of the following
graphs correctly shows the induced current in the coil of wire and also the direction of the current as a function of the right edge of the loop of wire? (Positive current is deﬁned as in
the clockwise direction around the coil of wire.) 3) Question 2. A uniform Bﬁeld, Bo enters a closed surface through a face of area 2A0. The same ﬁeld
lines exit uniformly through the back surface of area A0. What is the strength of the exiting
Bﬁeld? BO B [a] B0 [19] I [C] "2i [d] 230 [e] 430 Question 3. The magnetic ﬁeld of the earth at its surface is of order; [a] 10"2 gauss [b] lgauss [c] lOOgauss {d} lTesla [e] 10 Tesla V2. r Question 4.
What is the power dissipated by the 100 ohm resistor? [a] 40mW
1009 [b] 0.02w
3V "W
W [c] 20 mA
TM/Wer ' [d] W
509 [e] 0.18W Question 5. When connecting ampmeters or voltmeters in a circuit which is the correct way to measure the
current and voltage in the load? [a] Ml Amp or Volt meter, M2 Amp or Volt meter
[b] Ml Volt meter , M2 Amp meter [c] Ml ~Amp meter, M2 Volt meter [(1] MlAmp or Volt meter, M2 Voltonly [e] Ml — Volt only, M2 Amp or Volt meter V2 r Question 6. A magnet as shown is brought near a
cathode ray tube. The electrons emitted
from the cathode follow a path through the
ﬁeld and then hit the screen. Where on the
cathode rays screen do the electrons hit? Question 7. A number of circular loop of wire are
near a straight wire carrying a .r current I as shown. When i is
increasing, which loops are subject
to a repulsive magnetic force? (Narrow profiles mean that they are 0 4
actually perpendicular to the page, seen edge on) [a] 1 and 2 [d] all of them
[b] 3 only [e] none of them
[c] 4 only Question 8. A cross section of a long conductor of a type called a coaxial cable is shown in the ﬁgure and
gives the radii (a, b, c). Equal but opposite currents I are uniformly distributed in the two
conductors colored gray. The expression for the magnetic ﬁeld B(r) in the ranges of b < r < a
is “01032 " 7'2) no”.
a] 2n r(a2 + [92) [d] 27: ab2
.E'PL 1101012 — r2)
[b] 22: a [8] 27m:2 — b2)
' 2 2
[C] ”01(‘1 — r ) 2n: r(czz — b2) V1 Question 11.. A circuit has a battery with a voltage of 10 V, resistor R1 = 10 Q, resistor R2 =
15 Q, and inductor L = 20 H. Switch S is closed for a very long time and
then opened to form an RL circuit. If R2 is a light bulb, how long wouid the
light bulb stay lit? (Assume the light bulb stays lit until the current from the
inductor is 10% of the initial current from the inductor once switch 8 is opened) [a] 0.14045 R.
[b] 4.605s [c] 3.0709 V '  R:
[d] 1.7273 3 [e] 1.151 3 Question 12. An ac source provides an emf of VAc(t) = V0 sin(0)t). When the angular
frequency 0;) is very large, what is the peak voltage across R2? [(1] Zero
[17} VD VoRz c
RI+R2 Question 9. The potential drop is 6.4uV across a resistor of resistance 1.00. How many
electrons enter the wire in 5 seconds? (note e = 1.6x10'530) [a] 3.2x1019 . R [b] 8.0X1015 _/\/\/\/_
2.5><1012 ’
[c] L_ V ‘_ [d] 2.0><10l4 [e]1.6><1019 Question 10. A 2 cm by 15 cm rectangular coil has 300 turns and rotates through the plane of the loop in a region
of uniform magnetic ﬁled of 0.4 Tesla. The magnetic ﬁeld is perpendicular to the axis of rotation. What must its rotational speed, cycles/sec, be to generate a maximum emf of llOVolts?
[a] 49 cycles/sec [b] 0.36 cycles/sec [c] 5 cycles/sec [d] 305 cycles/sec [e] 1 cycle/ sec Question 15. ‘
For the circuit shown find the current through the resistor RA. [a] 0.15 A
[b] 0.3 A [c] 0.45 A
[d] 0.67r A [e] 0.75 A V2. Question 13. A straight wire carrying a current I is bent into the shape shown.
Determine the net magnetic force on the wire, if the wire is in a uniform
magnetic field B directed along the yaxis (jaxis) [a] ZIBL in the +2 direction «I———'2L—I [b] ZIBL in the z direction [0] 4IBL in the +2 direction [d] 6IBL in the +2 direction _ [e] zero Question 14. in the figure shown what is the magnitude of the magnetic field at the
point P if a = 2.0cm, b = 5.0cm and l = 20 Amps? [a] 4.5 [4T 30
[b] 7.5 ,uT ’4). , r .. J'. Pni:~‘.. [[c] 9.0 “T I b ——n< ”9‘  [d] 6.0 in“ [e] 3 .6 [JT V2. Question 16. A thin nonconducting disk as a radius R and a uniform surface charge per
unit area a, spins with angular velocity on ,about an axis through the center of the disk and perpendicular to the plane of the disk. Find the magnetic
moment ,u of the spinning disk. 1
a —7rcrwR4 4 27mm
R 2 [b] 1
c —7rR20'w 2 [d] —1R2m2
27:0 1 22
—O'0)R
[6167: ...
View
Full Document
 Spring '08
 Wei

Click to edit the document details